Leaf Growth

Strawberry cultivar 'Rapella'grown in a glasshouse responded to shade with reductions in leaf area, number of leaves, crowns and inflorescences and shoot dry weight. There was no apparent interaction of shading and salinity on vegetative growth. Shading depressed the ...

Soil application of synthetic Fe(III)-chelates, mainly those derived from ethylendiamine di(o-hydroxyphenylacetic) acid (ED-DHA) and ethylendiamine di(2-hydroxy-4-methylphenylacetic) acid (EDDHMA), is the most effective, but the most expensive practice used to correct iron deficiency in plants growing on calcareous soils. Previous studies that compared the effectiveness of EDDHA/Fe 3+ and EDDHMA/Fe 3+ always used commercial products and their results are contradictory. In this study, the effectiveness of commercial EDDHA/Fe 3+ and EDDHMA/Fe 3+ fertilizers to correct iron chlorosis in three different crops (sunflower, peach and pear) was compared using doses calculated with the actual content of chelated iron determined by HPLC. The effectiveness of the Fe(III)-chelate derived from the ethylenediamine di(2-hydroxy-5sulfophenylacetic) acid (EDDHSA), that recently has been marketed as iron fertilizer, was also tested in the sunflower and pear experiments. For the three experiments, sev...

The spatial extent and timing of the impact of fish farms on the distribution and performance of a Posidonia oceanica meadow were examined in an embayment of the south-eastern coast of Spain (Hornillo Bay, Murcia). Changes in seagrass distribution were determined using available seagrass mapping (from 1988, i.e., before the onset of aquaculture activities and 1998) and by successive sampling in 1994 and 1998. Environmental variables (light attenuation coefficient, water-column dissolved nutrients and organic content of sediments) together with plant performance (shoot biomass, leaf growth rate, photosynthetic activity, carbohydrate reserves, the number of leaves per shoot, epiphyte loads and herbivore pressure) were measured in plants affected by organic discharges, and were compared with those found in reference healthy plants over an annual growth cycle. Since the onset of fish farm activity, 11.29 ha of P. oceanica meadow has been completely lost and 9.86 ha significantly degraded, thus resulting in a total affected area which accounts for about 53% of the former meadow, or 7-fold the fish farming area. Unequal propagation of seagrass die-off or degradation reflects the relevance of local factors such as depth and hydrodynamism on the true extent of fish farm impact. Water transparency decreases and dissolved nutrient and organic content of sediments increases in the vicinity of cages compared to distant reference stations, thus supporting the notion of environmental gradients caused by the organic release from cages, which spreads outwards. Shoot size, leaf growth rate and the number of leaves per shoot in plants close to the fish farm decreased. Moreover, low leaf growth and low rhizome carbohydrate concentration (always relative to that found in an undisturbed area) indicated carbon budget imbalances. Since light reduction in the affected area was only modest (31% of light reaching the sea surface, while at the same depth this figure was 39% at the reference site), and light availability was well above the minimum requirement estimated for this species, neither this factor nor epiphyte overgrowth (epiphyte load was lower in the affected area) seem to explain such carbon imbalances or the observed meadow regression. Alternatively, the high herbivore pressure found in the affected zone suggests that overgrazing is one of the main causes of decreasing shoot sizes and hence of carbon imbalance, reduced growth and shoot mortality. The impact of fish farms on seagrasses, therefore, seems to be highly variable and depends on complex interactions between a large number of processes.

For the mass production of chestnut trees with selected, hybrid, or genetically engineered genotypes, one potentially desirable propagation strategy is based on somatic embryogenesis. Although methods exist for the initiation of embryogenic cultures of Castanea sativa from immature zygotic embryos or leaf explants, the embryos produced have had low rates of conversion into plantlets. This study explored the possible benefits for somatic embryos that have already undergone maturation and cold treatments, of (a) partial slow or fast desiccation, and (b) of the addition of plant growth regulators or glutamine to the germination medium. Germination response was evaluated in terms of both conversions to plantlets and through embryos developing only shoots (shoot germination) that could be rooted following the micropropagation protocols developed for chestnut. Two or 3 wk slow desiccation in sealed empty Petri dishes resulted in a slight reduction in water content that nevertheless increased total potential plant recovery, shoot length, and the number of leaves per plantlet. However, best results were achieved by 2 h fast drying in a laminar flow hood, which reduced embryo moisture content to 57–58% and enhanced the potential plant recovery and quality of regenerated plantlets. Plant yield was also promoted by addition of 0.44 μM benzyladenine and 200–438 mg/l of glutamine to the germination medium, and plantlet quality (as evidenced by root, shoot, and leaf growth) by the further addition of 0.49 μM indole-3-butyric acid.

Over the past 14 years, long-term ecological research (LTER) was conducted on the desert perennial, Welwitschia mirabilis (Gnetales: Welwitschiaceae), located in the Welwitschia Wash near Gobabeb in the Central Namib Desert. We measured leaf growth of 21 plants on a monthly basis and compared this with climatic data. The population structure as well as its spatial distribution was determined for 110 individuals. Growth rate was 0.37 mm day−1, but varied 22-fold within individuals, fluctuating seasonally and varying between years. Seasonal patterns were correlated with air humidity, while annual differences were affected by rainfall. During three years, growth rate quadrupled following episodic rainfall events >11 mm during mid-summer. One natural recruitment event followed a 13-mm rainfall at the end of summer. Fog did not appear to influence growth patterns and germination. Plant location affected growth rate; plants growing on the low banks, or ledges, of the main drainage channel grew at a higher rate, responded better and longer to rainfall and had relatively larger leaves than plants in the main channel or its tributaries. This could be due to better water and nutrient conditions on the ledges than elsewhere. The population appears to be growing outwards, with the smallest (youngest?) plants highest. Sex ratio was male-biased and males grew larger than females. Our study, in conjunction with the extensive literature base on Welwitschia, published here in a bibliography comprising 297 papers, indicates the knowledge gaps and needs for further ecological studies, including the continuation of our LTER programme. This should elucidate the reproductive output, seed dispersal, recruitment, water availability, age structure, and ecological differences between the sexes, and long-term life history strategies. Such knowledge would contribute to desert ecology and improve the management strategies of this unique Namib Desert perennial.

Solvent leaf extracts of Terminalia catappa were evaluated for
their cytotoxic and their radical scavenging potential. Brine shrimp
assay was used for exploring cytotoxic activity, all the extracts
namely hexane, DCM, chloroform, acetone and methanol were
tested at the dose level of 25, 50, 100 and 200microgram /ml. A
dose dependent response was obtained in all the extracts.
Chloroform extract showed 100percent activity at the highest dose
of 200μg/ml. Antioxidant activity was evaluated by one
qualitative(TLC based) and two quantitative radical scavenging
assays namely DPPH (2, 2- Diphenyl-1- picryl hydrazyl) assay
and ferric reducing antioxidant power (FRAP) assay. In both
assays acetone extract exhibited significant reduction of free
radicals. The IC50 value of acetone extract was 36.9μg/ml.
Ascorbic acid was used in these assays as reference compound.
FRAP value of acetone extract was found to be 6.73 much higher
than all the other extracts.

Three Indian Brassica juncea cultivars were studied for embryogenic response of microspores, microspore embryo regeneration, ploidy assessment of microspore-derived plants and their diploidization. Genotype dependence for microspore totipotency was observed and a significant effect of genotype by bud size selection was established. The addition of activated charcoal in NLN medium containing 13% (w/v) sucrose and 10 μM silver nitrate resulted in a fourfold increase in microspore embryogenesis, ranging from 100 to 405 embryos per Petri dish corresponding to 2,700–10,935 embryos per 100 buds. Conversion/germination of embryos produced in presence or absence of activated charcoal was similar but air-drying of microspore embryos was essential. Incubation of microspore embryos at 4 ± 1°C for 10 days in dark resulted in 82.3% conversion. The majority of plants produced from these embryos was haploid. Treating microspore-derived plants at the 3–4 leaf growth stage with 0.34% colchicine for 2–3 h resulted in greatest survival (70%) and chromosome doubling (75%) frequencies. Doubled haploid plants were self-pollinated and grown to maturity under field conditions.

Under phosphorus deficiency reductions in plant leaf area have been attributed to both direct effects of P on the individual leaf expansion rate and to a reduced availability of assimilates for leaf growth. In this work we use experimental and simulation techniques to identify and quantify these processes in wheat plants growing under P-deficient conditions. In a glasshouse experiment we studied the effects of soil P addition (0–138 kg P2O5 ha-1) on tillering, leaf emergence, leaf expansion, plant growth, and leaf photosynthesis of wheat plants (cv. INTA Oasis) that were not water stressed. Plants were grown in pots containing a P-deficient (3 mg P g-1 soil) sandy soil. Sowing and pots were arranged to simulate a crop stand of 173 plants m-2. Experimental results were integrated in a simulation model to study the relative importance of each process in determining the plant leaf area during vegetative stages of wheat. Phosphorus deficiency significantly reduced plant leaf area and dry weight production. Under P-deficient conditions the phyllochron (PHY) was increased up to a 32%, compared to that of high-P plants. In low-P plants the rate of individual leaf area expansion during the quasi-linear phase of leaf expansion (LER) was significantly reduced. The effect of P deficiency on LER was the main determinant of the final size of the individual leaves. In recently expanded leaves phosphorus deficiency reduced the photosynthesis rate per unit leaf area at high radiation (AMAX), up to 57%. Relative values of AMAX showed an hyperbolic relationship with leaf P% saturating at 0.27%. Relative values of the tillering rate showed an hyperbolic relationship with the shoot P% saturating at values above 0.38%. The value of LER was not related to the concentration of P in leaves or shoots. A morphogenetic model of leaf area development and growth was developed to quantify the effect of assimilate supply at canopy level on total leaf area expansion, and to study the sensitivity of different model variables to changes in model parameters. Simulation results indicated that under mild P stress conditions up to 80% of the observed reduction in plant leaf area was due to the effects of P deficiency on leaf emergence and tillering. Under extreme P-deficient conditions the simulation model failed to explain the experimental results indicating that other factors not taken into account by the model, i.e. direct effects of P on leaf expansion, must have been active. Possible mechanisms of action of the direct effects of P on individual leaf expansion are discussed in this work.

Rice is an important food crop worldwide. Its productivity has been influenced by various abiotic and biotic factors including temperature, drought, salt, microbe, ozone, hormone and glyphosate. The responses of plants to stress are regulated by multiple signaling pathways, and the mechanisms of leaf growth and development in response to stress remain unclear to date. Recently, proteomics studies have provided new evidence for better understanding the mechanisms. The proteins in response to different stress conditions are mainly involved in photosynthesis, signal transduction, transcription, protein synthesis and destination, defense response, cytoskeleton, energy, cell wall and other metabolism. In addition, some stress type-specific proteins have been identified, such as small heat shock proteins under temperature stress, S-like RNase homolog and actin depolymerizing factor under drought stress, ascorbate peroxidase and lipid peroxidation under salt stress, probenazole-inducible protein and rice pathogenesis-related proteins under blast fungus. Many of the proteins including ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisCO), molecular chaperones, antioxidases and S-adenosylmethionine synthetase play very important roles in leaves. This paper reviews the proteomic characterization of rice leaves in response to various environmental factors.

Abstract. Sugarcane (Saccharum officinarum L.) an important sugar crop, shows high sensitivity to salinity at various growth stages. This study was conducted to determine the comparative response of a salt-tolerant (CP-4333) and a salt-sensitive (CP-71-3002) sugarcane clone to the ...

Methods were developed to assess and quantify the predictive quality of simulation models, with the intent to contribute to evaluation of model studies by non-scientists. In a case study, two models of different complexity, LINTUL and SUCROS87, were used to predict yield of forage maize under Dutch meteorological conditions. The models predict yield under potential conditions, i.e. temperature- and radiation limited yield, assuming other production factors to be optimal. After a review of concerns voiced in model-based applied research, the simulation models were described in a systematic manner to simplify access to the software code. A model analysis showed that the models contain switches, describing abrupt changes occurring in the crop (e.g. change of temperature driven leaf area growth to photosynthesis driven leaf growth; onset of leaf senescence). Some switches introduced discontinuities in the relation between state variables and parameters. Such properties make non-standard...