Leonardo Lombardini
The University of Georgia, Horticulture, Faculty Member
Research Interests:
A field experiment was conducted for 2 years (2019 and 2020) to determine the response to the application of Biochar (BC) obtained from the coffee pulp in combination with chemical fertilization (CF) in coffee trees. The established... more
A field experiment was conducted for 2 years (2019 and 2020) to determine the response to the application of Biochar (BC) obtained from the coffee pulp in combination with chemical fertilization (CF) in coffee trees. The established treatments were the edaphic application of different doses of BC (0, 4, 8, and 16 t ha−1) and levels of CF (0, 33, 66, and 100% of the nutritional requirements) on the physical (bulk density (ρa), stable aggregates), chemical (nutrient availability), and biological (respiration) properties of soil from a coffee crop. Regarding the physical properties, it was mainly observed that BC doses of 8 or 16 t ha−1 reduced ρa (0.82 and 0.83 g cm−3, respectively) and increased the aggregation status (96.5% and 96.84%, respectively) in comparison to 0 t ha−1 in 2020. The chemical properties showed that the application of 16 t ha−1 BC decreased about 60% of the exchangeable acidity (EA) compared to the control (0 t ha−1) whereas the pH (4.96 and 4.92) and organic car...
Research Interests:
Drought is one of the main abiotic stresses in coffee crop, and the use of biochar (BC) has been considered an alternative to mitigate this kind of stress. Plants of the Castillo variety were grown in pots and PVC pipes filled with silt... more
Drought is one of the main abiotic stresses in coffee crop, and the use of biochar (BC) has been considered an alternative to mitigate this kind of stress. Plants of the Castillo variety were grown in pots and PVC pipes filled with silt loam soil in two separate experiments to evaluate the effect of the coffee pulp biochar application on the physiological responses under water deficit conditions. Four different BC doses (0, 4, 8, and 16 t ha-1) were incorporated. Water deficit was imposed through the progressive reduction irrigation (25%, 50%, 75%, and 90% of water lost via evapotranspiration). Gas exchange, maximum quantum yield of PSII (Fv/Fm), biomass, and water status were measured. Reduced irrigation (RI) negatively affected Fv/Fm , leaf gas exchange, biomass, and water status. 8 t ha -1 (BC) increased photosynthesis in both well-irrigated (WI) plants (6 µmol m-2 s-1) or with RI (3.5 µmol m-2 s-1) compared to 0 t ha -1 BC (RI: 1.8 µmol m-2 s-1 and WI: 3.9 µmol m-2 s-1). To summarize, 8 t ha-1 BC can be a recommended practice for coffee production not only to capture carbon and reintroduce it to the soil, but also to alleviate the effects of moderate water deficit.
Research Interests:
CeO2NPs displayed concentration and coating property dependent effects on soybean photosynthesis and water use efficiency.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Carbohydrate translocation, which follows anatomical and developmental patterns, is ruled by source-sink relations where energycontaining compounds are moved from sources of production to sinks of utilization. Seasonal carbohydrate... more
Carbohydrate translocation, which follows anatomical and developmental patterns, is ruled by source-sink relations where energycontaining compounds are moved from sources of production to sinks of utilization. Seasonal carbohydrate concentrations in various tree parts were measured and compared in 10 cm (4 in) trunk diameter live oaks (Quercus virginiana P. Miller). Tissue samples from roots, trunks, twigs and leaves were collected from three-year-old field-grown trees on four dates throughout the 2005–2006 seasons. Laboratory analyses of glucose and starch were performed, and values were compared and contrasted according to sample location and time of year. Glucose levels were significantly higher in leaves during the winter (P ≤ 0.001), while starch concentrations were significantly higher in root and trunk tissues during the spring and winter assessments (P ≤ 0.001). Carbohydrate concentrations varied among tissues sampled within the tree. This study provides valuable information...
Research Interests:
Horticultural crops include a wide range of commodities, such as fruits and vegetables, that are highly valuable for humanity. They are extensively grown worldwide, and their production can be described as an open and highly complex... more
Horticultural crops include a wide range of commodities, such as fruits and vegetables, that are highly valuable for humanity. They are extensively grown worldwide, and their production can be described as an open and highly complex system affected by many factors, among which we can count weather, soil and cropping system, as well as the interaction between these factors. The aim of environmental physiology is to characterize the interaction between envi ronmental stress and crop response, in order to maximize both yield quantity and quality. This review presents the most recent findings about the effects of the main abiotic environmental factors (light, temperature, and water) on whole plant physiology of horticultural crops. Environmental stresses can cause morpho-anatomical, physiological and biochemical changes in crops, resulting in a strong profit reduction. A clear understanding of environmental factors and their interaction with physiological processes is extremely importan...
Research Interests:
Research Interests:
Tree transplanting practices influence plant survival, establishment, and subsequent landscape value. However, transplanting practices vary substantially within the horticultural industry. Of particular importance is the location of the... more
Tree transplanting practices influence plant survival, establishment, and subsequent landscape value. However, transplanting practices vary substantially within the horticultural industry. Of particular importance is the location of the root collar relative to soil grade at transplant. The objective of this study was to determine the effects of factorial combinations of planting depths, root collar at grade or 7.6 cm either above or below grade, and soil amendments on container-grown (11 L) Quercus virginiana Mill. Soil treatments included a tilled native soil (heavy clay loam, Zack Series, Zack-urban land complex, fine, montmorillonitic, thermic, udic paleustalfs), native soils amended with 7.6 cm of coarse blasting sand or peat that were then tilled to a depth of 23 cm, or raised beds containing 20 cm of sandy loam soil (Silawa fine sandy loam, siliceous, thermic, ultic haplustalfs). A significant (P ≤ 0.05) block by soil amendment interaction occurred for photosynthetic activity....
Research Interests:
A greenhouse experiment was conducted to evaluate the effects of water stress on leaf water potential, plant growth, and photosynthesis in purple passionflower (Passiflora incarnata). Twenty 4-L pots with two plants in each pot were... more
A greenhouse experiment was conducted to evaluate the effects of water stress on leaf water potential, plant growth, and photosynthesis in purple passionflower (Passiflora incarnata). Twenty 4-L pots with two plants in each pot were arranged in a completely randomized design. Ten pots received a daily irrigation dose of 100% evapotranspiration (ET) throughout the 43-day experiment (control). The other 10 pots were subjected to a reduced irrigation (RI) treatment, which was implemented stepwise to achieve a gradual increase in stress, by irrigating them with 50% ET first, then with 25% ET and, finally, with 10% ET. The last stress phase was followed by a recovery phase in which all treatments received the same amount of water (100% ET). A lower water potential was obtained at 10% ET compared with control plants (−2.51 and −0.98 MPa, respectively). Plants in both 25% and 10% ET irrigation treatments had reduced net CO2 assimilation rates (4.25 and 3.50 μmol·m−2·s−1, respectively) than...
Research Interests:
Research Interests:
The horticulture industry provides significant contributions to society, including healthy foods, economic development, recreation and leisure activities, among others. However, there are critical issues facing the horticulture industry... more
The horticulture industry provides significant contributions to society, including healthy foods, economic development, recreation and leisure activities, among others. However, there are critical issues facing the horticulture industry which should be illuminated to ensure ongoing vitality and relevance, particularly within the COVID-19 pandemic context. The present study used the Delphi Technique to identify the most critical issues facing the horticulture industry as perceived by a panel of industry experts. Data were collected from February to October 2020 and thus preceded the initial declaration of COVID-19 as a global pandemic through the lifting of stay-at-home orders in most states. The expert panel arrived at a consensus on 34 specific issues, five of which were specifically related to the COVID-19 pandemic. Using the Constant Comparative Method, the issues were thematically analyzed and grouped into five primary categories, including (alphabetically ordered): (1) disease ...
Ecotypic, clonal, and racial variation present in tree species across their native ranges represent a largely untapped opportunity to select superior seed sources or clonal materials to withstand a variety of unique environmental stresses... more
Ecotypic, clonal, and racial variation present in tree species across their native ranges represent a largely untapped opportunity to select superior seed sources or clonal materials to withstand a variety of unique environmental stresses imposed in built environments and managed landscapes. This paper focuses on three important woody plant genera (Quercus L., Platanus L., and Taxodium Rich.) and researchers’ efforts to discover superior genotypes with tolerances to environmental stresses, including alkaline soil conditions, moisture deficits, and temperature extremes. The study authors are also interested in exploiting geographic provenances and open-pollinated family selection to identify unique genotypes or populations having desirable ornamental attributes, rapid root regeneration potential, and/or desirable plant architecture. A discussion of current results, potential impacts on selection of urban forest trees for managed landscapes, and plans for future development and resear...
Research Interests:
With container-grown trees offered to the public in an increasing array of sizes, it is important to determine the effects of different sizes of container stock on transplant establishment. Clonal replicates of Vitex agnus-castus, Acer... more
With container-grown trees offered to the public in an increasing array of sizes, it is important to determine the effects of different sizes of container stock on transplant establishment. Clonal replicates of Vitex agnus-castus, Acer rubrum var. drummondii, and Taxodium distichum grown under common nursery conditions in five container sizes, 3.5, 11.7, 23.3, 97.8, or 175.0 L (#1, #3, #7, #25, or #45, respectively), were transplanted to a sandy clay loam field. Physiological stress was measured using xylem water potential and photosynthetic gas exchange rates. Height, trunk diameter, and canopy spread were monitored post-transplant for three growing seasons and root growth was sampled for the first two growing seasons. Trees of all three species from smaller-sized containers, 23.3 L (#7) or less, exhibited reduced transplant shock, decreased establishment time and increased growth rates in comparison to larger-sized containers, apart from increased mortality in 3.5 L (#1) A. rubrum...
Research Interests:
Research Interests:
Research Interests:
The claim that organic agriculture produces higher levels of phytochemicals has been controversial for decades. Using strawberries as a model crop in field conditions, a preharvest leaf wounding stress was applied to study the production... more
The claim that organic agriculture produces higher levels of phytochemicals has been controversial for decades. Using strawberries as a model crop in field conditions, a preharvest leaf wounding stress was applied to study the production of phytochemicals in fruits. As a result phenolic compounds (PCs) and total soluble sugars increased significantly, where specific phenylpropanoids showed increment up to 137% and several genes related to PCs biosynthesis and sugar transport were overexpressed. It was observed that the accumulation of PCs on fruits can be triggered by the application of wounding stress in a distant tissue and this accumulation is directly related to carbon partition and associated gene expression. This supports the idea that higher levels of healthy phytochemicals reported in organic fruits and vegetables could be due to the wounding component of the biotic stress attributed to insects to which the plant are exposed to.
Pecan tree pruning is a standard cultural practice in commercial pecan farming operations. Pruning often promotes canopy light infiltration, air movement, and crop load management. Timing of pecan tree pruning is often during winter for... more
Pecan tree pruning is a standard cultural practice in commercial pecan farming operations. Pruning often promotes canopy light infiltration, air movement, and crop load management. Timing of pecan tree pruning is often during winter for labor and time management purposes, yet the most effective pruning time is not known for pecan. `Pawnee' trees were pruned during March (winter), May, June, July and August in a commercial orchard in Charlie, Texas during the 2003 and 2004 growing seasons. June pruning produced the greatest two year summed annual average yield (2447.7 kernel lb/acre), largest increase of kernel lb/acre (625%) and largest increase percent kernel (113%) between 2003 and 2004. Furthermore, June produced the largest nuts (39.8 nuts/lb) with the lowest yield (337.5 kernel lbs/acre) in 2003, and smallest nuts (59.4 nuts/lb) with the highest yield (2110.2 kernel lb/acre) in 2004. March pruning produced the least variable yield of kernel lb/acre (38% decrease) between 20...
Research Interests:
Over the past decade, renewed emphasis has been placed on extension services in developing countries to reduce rural poverty and improve food security. Despite this emphasis, complex physical, political, and socioeconomic environments in... more
Over the past decade, renewed emphasis has been placed on extension services in developing countries to reduce rural poverty and improve food security. Despite this emphasis, complex physical, political, and socioeconomic environments in developing countries pose significant difficulties to extension agents’ success rates of adoption of new practices and/or behavior change among rural populations. In addition, agents have meager resources at their disposal. Development programs in the health sector have had success with employing behavior change theories for program design, driven by the Barrier Analysis as a method for gathering data about target populations. Theory and research suggest this method provides key information about why a target population might adopt new practices. If extension agents in developing countries such as Guatemala had access to such information, they might intentionally design interventions that lead to adoption. This paper provides an examination of examp...
Research Interests:
Water relation parameters were calculated from analysis of 92 pressure-volume isotherms of leaves of two olive varieties, `Leccino' and `Frantoio', measured after 4 weeks of salinity stress and 4 weeks of subsequent relief either... more
Water relation parameters were calculated from analysis of 92 pressure-volume isotherms of leaves of two olive varieties, `Leccino' and `Frantoio', measured after 4 weeks of salinity stress and 4 weeks of subsequent relief either in hydroponics or soil culture. `Frantoio' was more salt-tolerant than `Leccino', but no major differences in water relation parameters emerged between the two varieties. Increasing salinity from 0 to 200 mM NaCl decreased predawn leaf water potential from –0.5 MPa to –1.3 MPa, relative water content (RWC) from 97.6% to 89%, and leaf osmotic potential (Ψπ) from –2.0 to –3.5 MPa. Relative water content at turgor loss point (RWCtlp) was decreased from 89% to 85% (soil culture) and from 86% to 80% (hydroponic culture) in 0 to 200 mM CaCl-treated plants, respectively; a lower RWCtlp was also retained during the relief from salinity. Active osmotic adjustments induced by salinity was the result of accumulation of both inorganic ions and compatibl...
Research Interests:
Aleppo Pine (Pinus halepensis Mill.) is known to be the most drought-resistant Mediterranean Pine. This species is widely distributed throughout the Mediterranean region and displays a high intraspecific variability, with respect to its... more
Aleppo Pine (Pinus halepensis Mill.) is known to be the most drought-resistant Mediterranean Pine. This species is widely distributed throughout the Mediterranean region and displays a high intraspecific variability, with respect to its physiological and morphological response to environmental conditions. In this experiment we evaluated the response of Pinus halepensis seedlings to drought. Sixty germinated seeds (accession A6, Shaharia, Israel) were grown in soil for 8 weeks and then transferred to black plexiglass tanks containing half-strength air-sparged Hoagland solution. After 6 weeks of acclimation to hydroponics, the osmotic potential of the solution was lowered by adding polyethylene-glycol (PEG) 8000. Water potential was lowered in 0.2 MPa increments every 4 days, until a final value of –0.8 was reached. The seedlings were then maintained at –0.8 MPa for a further 8 days. Ultrasonic acoustic emissions, pressure–volume (P–V) curves, shoot and root growth, leaf area, xylem d...
Research Interests:
Instrumentation to measure soil respiration is currently readily available. However, the relationship between soil respiration and root activity or root mass is not known. Herein we report on preliminary result using a 13CO2 pulse to the... more
Instrumentation to measure soil respiration is currently readily available. However, the relationship between soil respiration and root activity or root mass is not known. Herein we report on preliminary result using a 13CO2 pulse to the foliage to determine if 13C respiration can be related to either root activity or root mass. An experiment was performed in the field on a 5-year-old apple tree (cv. Jonagold on M7). The tree canopy was enclosed in a Mylar® balloon and 2.1 g 13CO2 were pulsed in the balloon for 1 hr. After the pulse, air emitted by the soil and selected roots was collected every 6 hr for 8 days, by bubbling it in 2 M NaOH. 13C/12C ratios were measured with the mass spectrometer. The emission of 13CO2 from the roots gradually increased after the pulse reaching a peak after 100 hr. The emission trend was not linear, but it seemed related to soil temperature. Leaves and fruit were also collected daily. 13C content in leaves was 1.15% right after the pulse, but it progr...
Research Interests:
The recent development of small portable infrared thermometers has made canopy temperature an easily measured characteristc in the field. Our objective was to correlate a reduction of soil water with foliage temperature and to compare it... more
The recent development of small portable infrared thermometers has made canopy temperature an easily measured characteristc in the field. Our objective was to correlate a reduction of soil water with foliage temperature and to compare it with other indicators of plant stress (Pn, E, gs, leaf expansion, sap flow). During Summer 1998, we evaluated the responses of potted apple rootstocks (cultivars Budagowski 9, M9, and Mark) to soil water deficit. Irrigation was withheld for 7 days, and the canopy temperature (Tc) was measured daily with an infrared camera. Tc was always higher than air temperature (Ta). Tc between control and stress plants began to differentiate from day 3. In Mark, this difference was maintained until the end of the experiment. However, gas exchange in Mark seemed to be less affected by the stress than in the other two cultivars. At day 7, midday stomatal conductance (gs) was 38.0, 32.3, and 72.0 mmol·m–2·s–1 in Budagowski 9, M9, and Mark, respectively (control val...
Research Interests:
Trials were established in Summer 2002 and 2003 to test the consequences of the application of a kaolin-based particle film (Surround WP, Engelhard Corp.) on gas exchange, nut quality, casebearer density and population of natural... more
Trials were established in Summer 2002 and 2003 to test the consequences of the application of a kaolin-based particle film (Surround WP, Engelhard Corp.) on gas exchange, nut quality, casebearer density and population of natural predators (insects and arachnids) on pecan (Carya illinoinensis, cv. `Pawnee') trees. Film application started immediately after bud break and was repeated every 7-10 days for seven (2002) or nine (2003) times during the season. On both years, treated trees frequently showed lower leaf temperature (up to 4 °C) than untreated trees. Leaf net assimilation rate, stomatal conductance and stem water potential were not affected by film application. Nut size and quality did not differ between the two treatments. In 2003, shellout (percentage of nut consisting of kernel) was in fact 54.2% and 55.5% for treated and control trees, respectively. Moreover, the two treatments yielded similar percentage of kernel crop grading as fancy, choice, standard and damaged. S...
Research Interests:
Pecans nuts from `Kanza' and `Desirable' cultivars were irradiated with 0, 1.5, and 3.0 kGy using electron beam (E-beam) irradiation and stored under accelerated conditions (40 °C and 55% to 60% RH). Antioxidant capacity (AC),... more
Pecans nuts from `Kanza' and `Desirable' cultivars were irradiated with 0, 1.5, and 3.0 kGy using electron beam (E-beam) irradiation and stored under accelerated conditions (40 °C and 55% to 60% RH). Antioxidant capacity (AC), phenolic (TP) and condensed tannin (CT) content, HPLC phenolic profile, tocopherol content, peroxide value (PV), and fatty acid profile were evaluated in kernels after 0, 7, 21, 55, and 134 days of storage. Irradiation had no detrimental effects in AC and TP; however, variation was found throughout storage. Tocopherol content of 1.5 and 3.0 kGy kernels decreased after irradiation, but no further decrease was observed thereafter. Irradiated `Desirable' samples had greater PV than controls, while `Kanza' 1.5 kGy samples had increased PV only after 134 days of storage. No change in fatty acid composition was detected for any cultivar. Color modification induced by storage included a decrease in lightness and yellowness and an initial increase of r...
Research Interests:
Planting depth during container production may influence plant growth, establishment, and subsequent landscape value. A lack of knowledge about the effects of common transplanting practices may lead to suboptimal performance of planted... more
Planting depth during container production may influence plant growth, establishment, and subsequent landscape value. A lack of knowledge about the effects of common transplanting practices may lead to suboptimal performance of planted landscape trees. Planting depth, i.e., location of the root collar relative to soil grade, is of particular concern for posttransplant tree growth both when transplanted to larger containers during production and after transplanting into the landscape. It is unknown whether negative effects of poor planting practices are compounded during the production phases and affect subsequent landscape establishment. This study investigated effects of planting depth during two successive phases of container production (10.8 L and 36.6 L) and eventual landscape establishment using lacebark elm (Ulmus parvifolia Jacq.). Tree growth was greater when planted at grade during the initial container (10.8 L) production phase and was reduced when planted 5 cm below grade...
Research Interests:
Seedlings from 13 open-pollinated families of Taxodium distichum (L.) L.C. Richard from the gulf coast, central and south Texas, and Mexico were grown in a nursery in College Station, Texas. Forty seedlings per family were measured on... more
Seedlings from 13 open-pollinated families of Taxodium distichum (L.) L.C. Richard from the gulf coast, central and south Texas, and Mexico were grown in a nursery in College Station, Texas. Forty seedlings per family were measured on three dates during the production cycle; 99, 109, and 133 days after sowing in Spring and Summer 2004. A two-step cluster analysis based on height and trunk diameter created 3 clusters of families. Cluster 1 had a mean height of 32 cm and a mean trunk diameter of 3.3 mm. Cluster 2 had a mean height of 33 cm and a mean trunk diameter of 3.4 mm. Cluster 3 had a mean height of 43 cm and a mean trunk diameter of 4.1 mm. Although clusters 1 and 2 are statistically significantly different, practically there is little difference between the two. The families from Mexico and central Texas were all in cluster 1 or 2 and the families collected from the gulf coast were all placed in cluster 3, with the exception of a single family from Biloxi, Miss., which was pl...
Research Interests:
An assessment of anatomical traits of pecan cultivars (`Pawnee', `Mohawk', and `Starking hardy giant') collected from three locations (Tifton, Ga.; Chetopa, Kans.; and Stillwater, Okla.) was conducted at Texas A&M University.... more
An assessment of anatomical traits of pecan cultivars (`Pawnee', `Mohawk', and `Starking hardy giant') collected from three locations (Tifton, Ga.; Chetopa, Kans.; and Stillwater, Okla.) was conducted at Texas A&M University. The objective of the study was to provide an understanding of patterns of geographic variation within the natural range for anatomical (stomatal density, stomatal index, and epidermal cell density) traits. Microscopy using acetate casts was used as the means to investigate the patterns of variation in the epidermal characteristics of pecan leaf. `Starking hardy giant' had the greatest number of stomates/cm2 (46,229, 47,807, and 45,990 at Tifton, Chetopa, and Stillwater, respectively) while `Mohawk' had the least (37,397, 36,217, and 35,305). `Pawnee' had the greatest number of epidermal cells/cm2 (251,806, 250,098 and 254,883 at Tifton, Chetopa, and Stillwater, respectively) while `Starking hardy giant' had the least (141,699, 138,40...
Research Interests:
Trials were conducted during summer months of 2002 and 2003 to evaluate the effects of a kaolin-based particle film (Surround WP, Engelhard Corp.) on gas exchange, nut quality, casebearer density and population of natural enemies (insects... more
Trials were conducted during summer months of 2002 and 2003 to evaluate the effects of a kaolin-based particle film (Surround WP, Engelhard Corp.) on gas exchange, nut quality, casebearer density and population of natural enemies (insects and arachnids) on pecan (Carya illinoinensis `Pawnee') trees. Film application was repeated for seven (2002) or nine (2003) times during the growing season. In both years, treated trees showed lower leaf temperature (up to 4 °C) than untreated trees. During the warmest hours of the day, kaolin-treated leaves were generally 0 to 2 °C cooler than air temperatures, compared to 4 to 6 °C for control leaves. Leaf net assimilation rate, stomatal conductance and stem water potential were not affected by film application. Nut size and quality did not differ between the two treatments. Shellout (percentage of nut consisting of kernel) was not affected by treatment and averaged about 55%. Crop grade distribution (fancy, choice, standard, and damaged) was...
Research Interests:
The Texas Pecan Board was established in 1998 to administer the Texas Pecan Checkoff Program and is financed through a half cent per pound assessment on grower pecan sales. The Board spends the assessment collections on a variety of... more
The Texas Pecan Board was established in 1998 to administer the Texas Pecan Checkoff Program and is financed through a half cent per pound assessment on grower pecan sales. The Board spends the assessment collections on a variety of advertising campaigns in an attempt to expand demand for Texas pecans and to increase the welfare of Texas pecan growers. This article presents an evaluation of the economic effectiveness of the Texas Pecan Checkoff Program in expanding sales of Texas pecans. First, the effects of Texas Pecan Board promotion on sales of all Texas pecans are determined using the ordinary least squares estimator followed by a test for differential effects of Texas Pecan Board promotion activities on sales of improved and native Texas pecan varieties using the seemingly unrelated regression estimator. The analysis indicates that the Texas Pecan Checkoff Program has effectively increased sales of improved varieties of Texas pecans but has had no statistically measurable impa...
Research Interests:
Insufficient fruit retention limits profitability of certain pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars. The present study examined efficacy of aminoethoxyvinylglycine (formulated as ReTain®; Valent BioSciences,... more
Insufficient fruit retention limits profitability of certain pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars. The present study examined efficacy of aminoethoxyvinylglycine (formulated as ReTain®; Valent BioSciences, Libertyville, IL), a natural ethylene inhibitor, for increasing crop-load through increased fruit retention in pecan trees grown at three distinct locations within the U.S. pecan belt. Several years of field studies found that timely postpollination ReTain® sprays [132 mg·L−1 a.i. (11.7 oz./acre)] to canopies could increase fruit retention of ‘Desirable’ and increase crop yield by 16% to 38% in trees carrying a “moderate to heavy” crop. ReTain® did not detectably increase fruit retention on trees carrying a “light” crop-load. The ReTain®-associated increase in yield of “heavy” crop-load trees did not necessarily decrease subsequent year yield. ReTain® appears to offer commercial potential as a crop-load management tool for ‘Desirable’ through regulation of Stag...
Research Interests:
Twenty-five-year-old `Cape Fear', `Desirable', and `Kiowa' pecan [Carya illinoinensis (Wangenh.) C. Koch] trees were either not pruned, or subjected to single selective or mechanical pruning using a mechanical hedger [or hedge... more
Twenty-five-year-old `Cape Fear', `Desirable', and `Kiowa' pecan [Carya illinoinensis (Wangenh.) C. Koch] trees were either not pruned, or subjected to single selective or mechanical pruning using a mechanical hedger [or hedge pruning (HP)] in the dormant season 2003. Canopy light interception, yield, and nut quality were monitored during a period of three years. Leaf area index and light interception were significantly affected during the first growing season after treatment application, but after three years canopies grew back to control levels. In general, there were small positive effects observed on yield and nut quality after pruning. Minor improvements were recorded for `Desirable', in which yield was affected positively by both pruning strategies in 2004. However, most effects disappeared by the third year. `Desirable' responded better than `Cape Fear', whereas no beneficial effects were recorded on `Kiowa'. In 2005, yield was significantly reduce...
Research Interests: Horticulture, NUTS, Yield, Profit, Hedging, and 4 moreLeaf Area Index, Pruning, Short Term, and Horticultural production
The objective of this study was to evaluate kernels of different pecan (Carya illinoinensis) cultivars for their antioxidant profile and their contribution to nutritional and quality attributes. Kernels were analyzed for their antioxidant... more
The objective of this study was to evaluate kernels of different pecan (Carya illinoinensis) cultivars for their antioxidant profile and their contribution to nutritional and quality attributes. Kernels were analyzed for their antioxidant capacity (AC), phenolic, tannin, and vitamin C content. Fatty acid (FA) composition and phenolic profile were determined using, respectively, gas and liquid chromatographic techniques. AC was measured using one spectrophotometrical [2,2-diphenyl-1-picrylhydrazyl (DPPH)] and one fluorescence method [oxygen radical absorbance capacity (ORAC)]. Phenolic and tannin content were determined using spectrophotometrical assays. Ascorbic and dehydroascorbic acid were determined using a HPLC. Both AC methodologies gave similar results with marked differences between cultivars. `Desirable' had an antioxidant capacity of 47,747 μg·g-1 TEq/DW with DPPH method followed closely by `Cheyenne' (36,192 μg·g-1 TEq/DW) and, with smaller amounts, by `Cape Fear&#...
Research Interests:
Pecan is a riparian species distributed over an area of geographic and climatic variation; such a wide distribution produces exposure to varied environmental conditions, providing a potential for genetic adaptation within the cultivars.... more
Pecan is a riparian species distributed over an area of geographic and climatic variation; such a wide distribution produces exposure to varied environmental conditions, providing a potential for genetic adaptation within the cultivars. Genotypes can be screened in order to obtain more drought tolerant cultivars using indirect screening parameters (chlorophyll fluorescence, osmotic adjustment, and abscisic acid assay) based on physiological responses of plants to abiotic stress conditions. A study was established at Texas A&M University, College Station, using a mixture of fritted clay (Quick dry) and pure sand in 1:1 (by weight) ratio to study the effects of drought on pecan rootstocks. The experiment was set up with the three water potential levels as treatments (–0.033 MPa, –0.1 MPa, –0.3 MPa) in a randomized complete-block design with three blocks. Measurements will include leaf water relations (relative water content, leaf water potential, osmotic adjustments, etc.), gas exchan...
Research Interests:
A greenhouse study was conducted to evaluate the response of four garden roses (Rosa ×hybrid L.), ‘RADrazz’, ‘Belinda’s Dream’, ‘Old Blush’, and ‘Marie Pavie’, to drought stress. Plants grown in containers were subjected to two watering... more
A greenhouse study was conducted to evaluate the response of four garden roses (Rosa ×hybrid L.), ‘RADrazz’, ‘Belinda’s Dream’, ‘Old Blush’, and ‘Marie Pavie’, to drought stress. Plants grown in containers were subjected to two watering treatments, well-irrigated [water as needed: ≈35% substrate moisture content (SMC) at re-watering] and cyclic drought stress (withholding irrigation until plants exhibit incipient wilting: ≈10% SMC, then re-watering to field capacity for subsequent dry down). Shoot growth and flower number were reduced in the drought treatment compared with the well-irrigated plants in all cultivars with least reduction in ‘RADrazz’. Drought stress reduced root growth in ‘Belinda’s Dream’ and ‘Marie Pavie’, whereas there was no difference in root growth in ‘RADrazz’ and ‘Old Blush’. Decreased SMC induced reduction in net photosynthetic rate (Pn), stomatal conductance (gS), transpiration rate (E), and midday leaf water potential (ψ). Leaf water use efficiency (WUE) in...
Research Interests:
Wilting during shelf life is a major cause of postharvest shrink for bedding plants shipped long distances from production greenhouses to retail outlets. The objective of this research was to determine if irrigation at lower, constant... more
Wilting during shelf life is a major cause of postharvest shrink for bedding plants shipped long distances from production greenhouses to retail outlets. The objective of this research was to determine if irrigation at lower, constant substrate moisture content (SMC) during greenhouse production would be a feasible way to acclimate plants for reduced shrinkage during shelf life while potentially conserving irrigation water. In two separate experiments conducted in the fall and spring seasons, rooted plugs of Angelonia angustifolia ‘Angelface Blue’ (angelonia) were grown in greenhouse production until a marketable stage in substrates irrigated at SMC levels of 10%, 20%, 30%, and 40% using a controlled irrigation system. At the end of the greenhouse production stage, plants were irrigated to container capacity and subjected to a simulated shipping environment in shipping boxes in the dark for 2 days. After shipping, plants were placed back in the greenhouse and watered minimally to si...
Research Interests:
The objective of this study was to assess the changes in leaflet zinc (Zn), leaf nutritional state, vegetative and physiological parameters, and yield quality in pecan trees sprayed with different Zn compounds. Eight-year-old ‘Western... more
The objective of this study was to assess the changes in leaflet zinc (Zn), leaf nutritional state, vegetative and physiological parameters, and yield quality in pecan trees sprayed with different Zn compounds. Eight-year-old ‘Western Schley’ pecan trees grafted to native seedlings were treated with ZnNO3 (100 mg·L−1 Zn), Zn-EDTA (50, 100, and 150 mg·L−1 Zn), and Zn-DTPA (100 mg·L−1 Zn) and compared with the Zn-untreated control. After 3 years of evaluation, the trees with the best appearance were those treated with ZnNO3 (100 mg·L−1 Zn) and Zn-DTPA (100 mg·L−1 Zn), which showed leaf Zn concentration increases of 73% and 69%, respectively, when compared with the controls. The chlorophyll values of the Zn-treated trees reached 46 SPAD units, equivalent to 43 mg·kg−1 dry weight (DW) of chlorophyll compared with values of 22 mg·kg−1 DW in Zn-deficient leaves. On a leaf area basis, chlorophyll value was 37% lower under Zn deficiency conditions than that of Zn-treated trees. Nut quality ...
Research Interests:
An assessment of leaf anatomic traits of pecan [Carya illinoinensis (Wangenh.) C. Koch] cultivars (Pawnee, Mohawk, and Starking Hardy Giant) collected from three locations (Tifton, GA; Chetopa, KS; and Stillwater, OK) was conducted to... more
An assessment of leaf anatomic traits of pecan [Carya illinoinensis (Wangenh.) C. Koch] cultivars (Pawnee, Mohawk, and Starking Hardy Giant) collected from three locations (Tifton, GA; Chetopa, KS; and Stillwater, OK) was conducted to provide an understanding of patterns of ecogeographical variation within the natural range. Acetate casts of representative leaves were prepared for microscopic characterization of epidermal traits (stomatal density, stomatal index, and epidermal cell density). There were differences among the three pecan cultivars at the same location, but there were no differences in stomatal density within the same cultivar grown at three distinct locations. The stomatal density of ‘Pawnee’ leaves (404 stomata/mm2) was intermediate between that of ‘Mohawk’ (363 stomata/mm2) and ‘Starking Hardy Giant’ (463 stomata/mm2). ‘Pawnee’ had the greatest epidermal cell density (2511 cells/mm2) whereas ‘Starking Hardy Giant’ showed the least (1414 cells/mm2). Within a location...
Research Interests:
A study was conducted to characterize the morphological and physiological responses of four herbaceous perennial species subjected to two subsequent drought cycles. Lantana camara L. `New Gold' (lantana), Lobelia cardinalis L.... more
A study was conducted to characterize the morphological and physiological responses of four herbaceous perennial species subjected to two subsequent drought cycles. Lantana camara L. `New Gold' (lantana), Lobelia cardinalis L. (cardinal flower), Salvia farinacea Benth. `Henry Duelberg' (mealy sage), and Scaevola aemula R. Br. `New Wonder' (fan flower) were subjected to two consecutive 10-day drought cycles. Growth response, leaf gas exchange, and chlorophyll fluorescence were measured during the experiment. The morphology of L. cardinalis and L. camara was not affected by drought, while S. farinacea had reductions in plant height and leaf area and S. aemula had reductions in dry weight. Overall, plant growth and development continued even when substrate water content was reduced to 0.13 mm3·mm-3, which indicated a level of substrate water below container capacity was sufficient for greenhouse production of these species. The drought treatments had little effect on the ph...
Research Interests:
After an outbreak of blotch leafminer (Cameraria caryaefoliella) on field-grown pecan (Carya illinoinensis) trees in 2010, an experiment was conducted to evaluate the consequences of the injury on carbon assimilation and photosynthetic... more
After an outbreak of blotch leafminer (Cameraria caryaefoliella) on field-grown pecan (Carya illinoinensis) trees in 2010, an experiment was conducted to evaluate the consequences of the injury on carbon assimilation and photosynthetic efficiency, and, in particular, to assess if low-to-moderate injury induces a compensatory increase in photosynthesis. Gas exchange and light-adapted fluorescence were measured on non-injured portions of the leaflet lamina adjacent to the injured area as well as on portions of leaflets that included leafminer injury. Results indicate that damage of the photosynthetic apparatus did not extend beyond the injured areas by leafminers. Furthermore, although a strong relationship between the proportion of leafminer injury and area-based net CO2 assimilation rate of injured leaflet tissue was found, there was no evidence that pecan leaves were able to compensate for leafminer injury by upregulating CO2 assimilation in leaflet tissue that was unaffected.
Research Interests:
An experiment was conducted to investigate the morphologic characteristics and photosynthetic response of sun and shade leaves of mature pecan [Carya illinoinensis (Wangenh.) K. Koch] trees. Treatments were established according to leaf... more
An experiment was conducted to investigate the morphologic characteristics and photosynthetic response of sun and shade leaves of mature pecan [Carya illinoinensis (Wangenh.) K. Koch] trees. Treatments were established according to leaf type (sun or shade leaves) and cultivar (Pawnee and Stuart). Sun leaves were chosen from those growing on exterior portions of the tree canopy and exposed to full sunlight for most of the day [≥1500 μmol·m−2·s−1 photosynthetic photon flux (PPF)]. Shade leaves were those growing in interior parts of the tree canopy (≤100 μmol·m−2·s−1 PPF). Epidermis characteristics, leaf area, and chlorophyll (Chl) content were also measured. Results indicated that stomatal density (stomata/mm2), leaf area, and leaflet area were greater in sun leaves than in shade leaves in both cultivars investigated. Specific leaf area was greater in shade leaves than sun leaves. Chlorophyll fluorescence, total Chl content, Chl a, Chl b, and Chl a/b were unaffected by leaf type or c...
Research Interests:
Leaf anatomical traits of Mexican and U.S. pecan [Carya illinoinensis (Wangenh.) K. Koch] seedstocks grown in a single location were studied to determine patterns of ecogeographic variation within the natural range. Stomatal density was... more
Leaf anatomical traits of Mexican and U.S. pecan [Carya illinoinensis (Wangenh.) K. Koch] seedstocks grown in a single location were studied to determine patterns of ecogeographic variation within the natural range. Stomatal density was uniform among open-pollinated seedlings of a common maternal parent with twofold differences in stomatal density separating some seedstocks. There was an inverse relationship between stomatal density and epidermal cell density. Stomatal density and stomatal index of Mexican seedstocks were related to longitude and annual precipitation of origin. Stomatal density increased along the longitudinal gradient toward the east coast of Mexico; seedstocks originating from areas on the east coast of Mexico had greater stomatal density than seedstocks originating from the drier areas on the west coast. Stomatal density and stomatal index did not follow a pattern along latitude or longitude in the U.S. seedstocks. Although isotopic carbon (13C) discrimination di...
Research Interests:
A study was conducted among the attendees of the Annual Texas Master Gardener Conference held in College Station, TX, in May 2006. Participants were asked to complete a 31-question survey to understand their knowledge of the nutritional... more
A study was conducted among the attendees of the Annual Texas Master Gardener Conference held in College Station, TX, in May 2006. Participants were asked to complete a 31-question survey to understand their knowledge of the nutritional attributes and storage guidelines of pecans (Carya illinoinensis). A total of 177 attendees completed the survey, corresponding to 32.2% of the total number of conference attendees. Participants were asked to complete the survey to test their nutritional knowledge, purchasing attitude, consumption, and storage preferences of pecans (23 questions). The remaining eight questions requested biographical and demographical information. Results revealed that taste was the main reason people ate pecans followed by the perception of eating something healthy. Over four-fifths of survey respondents knew that pecans contain heart-healthy fats and proteins. Approximately one-half of the respondents were aware that pecans are a source of minerals and antioxidants....
Research Interests:
A greenhouse study comparing the physiological responses and uptake of coffee (Coffea arabica L.) plants to foliar applications of zinc sulfate (ZnSO) and zinc nano-fertilizer (ZnO NPs) was conducted with the aim to understand their... more
A greenhouse study comparing the physiological responses and uptake of coffee (Coffea arabica L.) plants to foliar applications of zinc sulfate (ZnSO) and zinc nano-fertilizer (ZnO NPs) was conducted with the aim to understand their effects on plant physiology. One-year old coffee plants were grown in greenhouse conditions and treated with two foliar applications of 10 mg/L of Zn as either zinc sulfate monohydrate (ZnSO ‧ HO) or zinc oxide nanoparticle (ZnO NPs 20% w/t) and compared to untreated control plants over the course of 45 days. ZnO NPs positively affected the fresh weight and dry weight (FW and DW) of roots and leaves, increasing the FW by 37% (root) and 95% (leaves) when compared to control. The DW increase was 28%, 85%, and 20% in roots, stems, and leaves, respectively. The net photosynthetic rate increased 55% in response to ZnO NPs treatment at the end of experiment when compared to control. ZnO NPs-treated leaves contained significantly higher amounts of Zn (1267.1 ± 367.2 mg/kg DW) when compared to ZnSO-treated plants (344.1 ± 106.2 mg/kg DW), while control plants had the lowest Zn content in the leaf tissue (53.6 ± 18.9 mg/kg DW). X-ray micro-analyses maps demonstrated the increased penetrance of ZnO NPs in coffee leaf tissue. Overall, ZnO NPs had a more positive impact on coffee growth and physiology than conventional Zn salts, which was most likely due to their increased ability to be absorbed by the leaf. These results indicate that the application of ZnO NPs could be considered for coffee systems to improve fruit set and quality, especially in areas where Zn deficiency is high.