Compensatory Growth Responses During Reproductive Phase of Cowpea after Relief of Water Stress

Unpredictable drought affects growth and yield of dryland cowpea ( Vigna unguiculata [L.] Walp.) during rainy season. With the objective of identifying compensatory growth responses after relief of water stress, pot-grown plants (cv. C-752) were water-stressed at flowering, and physiological responses, short term dry matter partitioning upon relief of water stress, and productivity at maturity were studied. Water stress decreased, to varying degrees, leaf water potential, stomatal conductance, photosynthesis rate and transpiration rate. Recovery in assimilation lagged behind that in water relations. Assimilate supply seemed to be limiting early pod growth upon relief of water stress due to low photosynthesis rate, reduced leaf area per pod, and increased partitioning to leaf expansion. However, later pod growth was not limited by assimilate supply and final dry matter per pod was similar in both non-stressed and stress-affected plant. Cowpea exhibited the following growth responses during pod-fill stage upon relief of water stress: 1. increase in leaf area, 2. shift in dry matter partitioning in favour of leaf expansion, 3. extended green leaf duration, and 4. increase in pod number. These partially compensating physiological responses probably ensure reasonable productivity of dryland cowpea during rainy season.     

Effect of Post-Anthesis Water Stress on Accumulation of Dry Matter, Carbon and Nitrogen and Their Partitioning in Wheat Varieties Differing in Drought Tolerance

In four wheat ( Triticum aestivum L.) cultivars of tall (C306 and Narmada) and dwarf (HD2329 and Kundan) type, post-anthesis water stress affected the dry matter accumulation in plant parts with respect to main shoot controls. HD2329 among the dwarf types and Narmada 112 among the tall types were more adversely affected by stress, with greater reductions in their biomass and grain yield. Of the tolerant types, C306 (tall) showed a marginal reduction while Kundan (dwarf) had no reduction in these parameters as a result of stress. The results also indicated a varietal response to carbon and nitrogen accumulation and their partitioning in the main shoot when subjected to post-anthesis stress. In the susceptible dwarf cultivar HD2329, and in the susceptible tall cultivar Narmada 112, carbon and nitrogen contents were reduced in the grains of stressed main shoots. Of the tolerant cultivars, the dwarf type Kundan was not affected by stress, while the tall type C306 registered an increase in carbon content and its partitioning to grain.     

Dissipation of sulfosulfuron in soil and wheat plant under predominant cropping conditions and in a simulated model ecosystem

Environmental fate and dissipation of the sulfonylurea herbicide sulfosulfuron was investigated in soil (inceptisol) and wheat plant under predominant cropping conditions. Studies were conducted in natural field conditions and in a simulated model ecosystem. Thirty days after the wheat seeds had been sown, sulfosulfuron [N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-2-(ethylsulfonyl)imidazo[1,2-a]pyridine-3-sulfonamide] 75% w/w WG formulation was applied once in the field. The dosages were 25 and 50 g of active ingredient (ai)/ha. Studies were conducted in significantly separated individual plots to avoid contamination. In a predetermined interval, soil samples were collected and analyzed for the residues of sulfosulfuron. At harvest, wheat grain, straw, and soil samples were analyzed for the residues. Similar experiments were conducted in a model ecosystem. Apart from this, after harvest, the succeeding crops coriander (Coriandrum sativum) and edible amaranth (Amaranthus mangostanus L.) were raised in the model ecosystem and studied for the residues. No residues were detected in wheat grain, straw, and soil samples collected at harvest from both experiments or in the succeeding crops coriander and edible amaranth in the model ecosystem when tested at the minimum detection level of 0.001 microg/g. The dissipation of sulfosulfuron was found to have first-order kinetics in soil and plant in both studies. The dissipation data of sulfosulfuron in the model ecosystem were compared with those from the natural field conditions.     

De novo transcriptome assembly and development of EST-SSR markers for Pterocarpus santalinus L. f. (Red sanders), a threatened and endemic tree of India

Genetic Resources and Crop Evolution - The endemic and precious tree Pterocarpus santalinus L. f. (Red sanders) is a drought hardy species for conservation in peninsular India due to its...     

Transformation of Brassica oleracea var. capitata with bacterial betA gene enhances tolerance to salt stress

The bacterial betA gene for biosynthesis of glycinebetaine was transferred to cabbage (Brassica oleracea var. capitata) cultivar ‘Golden Acre’ through Agrobacterium-mediated transformation of hypocotyl explants. Transgenic status was established through Southern hybridization and mRNA expression in the shoots. The transformants exhibited higher tolerance to NaCl stress compared to untransformed parent plants. In physiological assessment of salinity tolerance, transgenics showed better growth response and greater stability in maintaining plant water relations at increasing levels of salinity. These results demonstrate that engineering glycinebetaine biosynthetic pathway into cabbage can lead to enhanced salt tolerance.     

Mechanical and physical characterization of sodium hydroxide treated Borassus fruit fibers

In order to improve the properties by chemical modification and to optimize the alkali concentration,we treated Borassus fruit fine fibers with aqueous sodium hydroxide solutions of different concentrations.In each case,the tensile properties of the fibers were determined.The morphology of the untreated and alkali treated fibers was observed using scanning electron microscope.The surface of the fibers became rough on alkali treatment.The tensile properties of the fibers improved on alkali treatment.The fibers attained maximum tensile properties when treated with 15% aqueous sodium hydroxide solution and decreased thereafter.The crystallinity index of the fibers showed a similar trend.The thermal stability of the alkali treated fibers was found to be higher than that of untreated fibers.Further,the char content was maximum for fibers treated with alkali having concentration of 15% and above.The chemical composition indicated that the percentageof α-cellulose was maximum when the fibers were treated with 15% aqueous sodium hydroxide solution and then decreased thereafter thus indicating the beginning of degradation of the fibers at higher concentrations.Thus,the optimum concentration of NaOH was established as 15% for alkali treatment of the Borassus fibers.     

Lipoxygenase Metabolites of α-linolenic Acid in the Development of Resistance in Pigeonpea, Cajanus cajan (L.) Millsp, Seedlings Against Fusarium udum Infection

Lipoxygenase (LOX) activity was measured in germinating pigeonpea Cajanus cajan seedlings, resistant (ICP-8863) and susceptible (ICP-2376) to wilt fungus, before and after infection with Fusarium udum. LOX activity was significantly higher in the resistant than in the susceptible cultivars of pigeonpea and was enhanced further in response to infection with Fusarium udum. This increase in LOX activity in the resistant cultivars of pigeonpea appears to be due to the induction of lipoxygenase isozymes in response to infection. Analysis of the endogenous LOX metabolites in pigeonpea seedlings revealed the predominant formation of 13-hydroperoxyoctadecadienoic acid (13-HPODE) in healthy seedlings and 13-hydroperoxyoctadecatrienoic acid (13-HPOTrE) in infected seedlings. Further studies on the effects of LOX metabolites on the growth and multiplication of Fusarium udum showed that HPOTrEs, LOX metabolites of -linolenic acid, are more anti-fungal compared to HPODEs, LOX metabolites of linoleic acid.     

Influence of Solar Radiation and Vapour Pressure Deficit on Transpiration Efficiency of Rainfed Sorghum

Besides assimilation, plant water relations are important aspects of physiological basis of productivity of crops in water limited environment. The relationships of photosynthesis rate, transpiration rate, leaf water potential and stomatal conductance with photosynthetically active radiation (PAR) and vapour pressure deficit (VPD) during pre-flowering (panicle initiation to ear emergence) and grain filling (from anthesis to maturity) stages of a sorghum hybrid (cv. CSH-6 ) grown under rainfed conditions were studied. Photosynthesis rate declined when PAR was above 1300 μmol m⁻² s⁻¹. during both the growth stages. Higher transpiration rate during grain filling stage at higher PAR caused the transpiration efficiency to be lower than during pre-flowering stage when PAR was above 1200 μmol m⁻²s⁻¹.Leaf water potential and stomatal conductance decreased with increase in PAR. Leaf water potential was higher during pre-flowering than during grain filling stage but maximum photosynthesis rate was similar during both the growth stages. Changes in VPD did not qualitatively alter the relationships of the physiological variables with PAR.
Decreasing photosynthesis rate and LWP at high PAR suggest that photosynthesis rate was limited by low leaf water potential when PAR was optimal, and by low PAR even when leaf water potential was high in rainfed sorghum during rainy season.     

椰子树叶鞘纤维增强体的结构特征

利用傅立叶红外光谱分析、化学分析、Ｘ射线和差热分析等方法,分析和评价了椰子树叶鞘纤维在制备绿色复合材料的用作纤维增强体适应性。用电镜扫描的方法研究了经碱处理和未处理的纤维形态。FTIR光谱分析和化学分析结果表明,经碱处理的纤维中半纤维素含量降低;Ｘ射线衍射证实碱处理的纤维结晶度增加。碱处理的纤维热稳定性略有增加,且抗拉性能也有所增加。综合机械和其他物理性能,这种椰子树叶鞘纤维增强体适用于制作绿色复合材料。     

Ammonia Metabolism in the Leaves and Ears of Wheat (Triticum aestivum L.) During Growth and Development

The pattern of free NH₄⁺ accumulation and its metabolism was studied during the growth and development of field-grown wheat cv. HD 2204 at two applied N levels viz. 30 and 120 kg ha⁻¹. The study was confined to the 3rd, 5th and flag leaf blades and the developing ears, borne on the main shoot, during their ontogeny. The NH₄⁺ levels were considerably lower in young leaves and increased sharply as the leaves senesced when the activity of glutamine synthetase (GS) declined. In contrast to GS, glutamate dehydrogenase (GDH) remained active even during senescence. Concentrations of protein, free amino acid and total reduced N declined with age in the leaves. An assessment of free NH₄⁺ pool, free amino acid content and the activity of GS and GDH in the floral parts revealed that glumes, awns and grains also were active sites of NH₄⁺ turnover. Higher applied N level not only increased leaf and grain N concentration but also led to higher free NH₄⁺ levels in leaves and in developing ears. Presence of NH₄⁺ in the entrapped transpirate revealed that NH₄⁺ is released from both leaves and ears during senescence.