Effects of NaCl Salinity on Growth and Production of Young Cladodes of Opuntia ficus-indica

The effects of salinity on the growth and production of `nopalitos' (young cladode sprouts) of Opuntia ficus-indica (L.) Mill. cv. Copena V-1 were investigated. Salinity (NaCl) irrigation levels with electrical conductivities of 2, 5, 10, 13, 18 and 21 dS m^–1 were used. In general, all cladode variables (stem area, number of young cladodes, length and width of cladodes, and fresh and dry weights) decreased with increasing salinity. The root-to-stem ratio and young cladode water content decreased significantly as salinity increased. Other variables that decreased with increasing salinity included harvest index, relative growth rate, stem area ratio, dry mass accumulation, and Na⁺ and Cl^– concentrations. For rooted cladodes, increased salinity decreased fresh weight, succulence, and root fresh weight, dry weight and length. Our conclusions suggest that this species is salt sensitive; however, there is some indication that it could be effectively managed in saline environments. Further studies and evaluation of different cultivars are needed to identify the mechanism of adaptation of salt tolerance in this species.     

Relationship between Water Content and Growth of Seed and Fibre of Three Cotton Genotypes

Three cotton genotypes (varying in their final seed size), viz. H-6 and H-4 ( Gossypium hirsutum L.) and V-797 ( Gossypium herbaceum L.) were studied for their growth kinetics of seed and fibre. Both biphasic linear and polynomial models were used to demark different phases of cotton seed growth. The polynomial model appeared to be appropriate to define the growth phases of cotton seed as compared to the linear model. The rate and the duration of dry matter accumulation were obtained by differentiating the best-fit polynomial equations. Based on the data of dry weight and water content, cotton seed development is divided into four different phases, viz. (a) cell division, (b) cell elongation, (c) dry matter accumulation and (d) maturation. The rate of dry matter accumulation showed a close correlation with water content of seed as well as of the fibre, in all three genotypes studied. It is proposed that water content of seed or fibre plays an important role in determining dry weight of three genotypes.     

Cotton Response to Salinity and Different Potassium-Sodium Ratio in Irrigation Water

The present study was designed to investigate cotton response to different salinity levels at different K/Na ratios of irrigation water.
The salinity levels in irrigation water were 3200 and 6400 mg/1 and the control treatment had a 320 mg/L. Potassium/Sodium ratios in irrigation water were 1: 9 and 1: 4.
Some agronomic traits were studied as well as leaf water Potential (LWP), and leaf samples were taken for elemental analysis.
Statistical analysis showed that increasing total salinity of irrigation water reduced seed yield and total dry weight of cotton but not number of total or open bolls. Lower K/Na ratio (1:9) was of benificial effects on most agronomic traits.
Increasing salinity of irrigation water caused an increase in Na, but not K or Ca content of the cotton leaves; while decreasing K/Na ratio in the saline irrigation water decreased the K/Na ratio in the leaves. Lower leaf water potential was found to be associated with higher levels of both water salinity and K/Na ratio.
A strong relationships were found between cotton seed yield, LWP and K/total bases content in leaves. Ionic content relations (K/Na and K/total bases content) were found to be of a strong association with LWP.
In brief, it could be concluded that increasing K to certain extent; K/Na (1: 9) could be useful in irrigating cotton plant with high water salinity.
The benificial effects of potassium additions to diminish the salinity effects in cotton may be the consequence of improved plant water relations, as well as the status of ion relationships.     

Effect of Soil Moisture on Relative Leaf Water Content, Chlorophyll, Proline and Sugar Accumulation in Wheat

The responses of four wheat ( Triticum aestivum L.) varieties to soil moisture were determined by measuring plant parameters such as relative leaf water content (RLWC) and the chlorophyll, proline and sugar contents of the leaf over two seasons. Two levels of irrigation treatments were adopted: irrigated and rainfed. The rainfed plants had consistently higher amounts of proline and sugar but lower RLWC and chlorophyll content. As drought intensified, differences between the irrigated and the rainfed plants with respect to all of these characters increased. The RLWC values of the irrigated plants were significantly higher in the morning but lower values were found at noon, showing some recovery in the afternoon.     

The Response of Four Sorghum Accessions/Cultivars to Salinity During Plant Development

Whole-plant-response of four sorghum accessions to increasing mM NaCl concentrations of 0, 100, and 150 was assessed at three growth stages (GS-1, GS-2, and GS-3), in a sand-culture experiment. Accession comparisons were made on the basis of absolute and relative salt tolerance values. Increasing salinity significantly reduced plant height at GS-1, whilst shoot and root dry weight were less affected. The effect of NaCl on these characters was greater at GS-2 and GS-3, and accessions differed significantly in their responses to salinity. On the basis of plant height data, Giza 114 had the highest absolute salt tolerance at all three growth stages. However based on shoot and root dry weight data, Double TX and Giza 114 were both significantly more NaCl-tolerant than INRA 133 and INRA 353 at GS-2. Based on relative salt tolerance values of shoot and root dry weight, and plant height, Double TX and Giza 114 were more affected by salinity at GS-3 than INRA 133 and INRA 353. INRA 133 and INRA 353 exhibited progressively higher tolerance at all growth stages, and produced more grains than Double TX and Giza 114 , and consequently had higher grain yield per plant. NaCl salinity had little effect on grain weight. Plant sensitivity to NaCl at three growth stages differs in the four accessions, and is genotype-specific. This suggests that there is considerable variation in salt tolerance in sorghum at the adult stage which may be exploited through selection and breeding of plants to effect further improvement in salinity tolerance in this species.     

The Effect of Short Warm Breaks during Chilling on Water Status, Intensity of Photosynthesis of Maize Seedlings and Final Grain Yield

The effects of short-term exposure of seedlings to suboptimal temperature (14 °C for 1 or 4 h in 24 h cycles) during chilling (5 °C for 12 days) on the water status and intensity of photosynthesis of tolerant (TG) and chilling-sensitive (SG) maize genotypes were studied. Daily warming for 1 or 4 h resulted in a decrease in the hydration of the seedlings to 31.1 % and 61.5 % (SG) and 14.8 % (TG) and 39.1 % (SG), respectively, in comparison with the continuously chilled control. During warming for 4 h, both genotypes absorbed water from soil in amounts that partly compensated for its loss through transpiration, after the plants had been moved to the lower temperature. A protective effect of shorter warming (1 h) on the hydration of the seedlings was a result of a strong, stomatal limitation of transpiration during the initial days of chilling. Warming for 1 or 4 h also increased the ability of TG stomata to close in reaction to water deficit in chilling conditions. The effect of increased temperature delayed the decrease of P_N in leaves and limited RGR inhibition of the seedling mass caused by chilling. Daily warming of plants at the seedling phase (14 and 20 °C for 1 or 4 h) reduced the unfavourable effect of chilling (5 °C for a period of 8 days) on the final yield, the filling of caryopses and their number in a cob after growth in natural conditions.     

Water Relations, Abscisic Acid and Yield of Wheat Plants in Relation to the Interactive Effect of Seawater and Growth Bioregulators

Irrigation of wheat plants with seawater (10 and 25 %) led to significant increases in free and bound abscisic acid (ABA) in leaves, especially at 25 %. The relative water content (RWC) and water use efficiency (calculated from grain yield, WUE_G, or from biomass yield, WUE_B) of the seawater-irrigated plants were lower than those of the control. Grain pre-soaking in gibberellic acid (GA₃), indole-3-acetic acid (IAA) or ABA reduced the levels of accumulated ABA (free and bound) produced by seawater irrigation. The stress imposed by seawater generally reduced yield and yield components of wheat plants and the effect was more pronounced at the higher level of seawater irrigation (25 %). Furthermore, seawater treatments decreased the carbohydrate content and increased the protein content of the developing grains. The effect of seawater treatments on ion concentrations in the developing grains was not consistent. The application of growth bioregulators appeared to mitigate the effect of seawater salinity stress on wheat productivity. GA₃ was the most effective hormone in this regard. The economic yield (grain yield) had a strong positive correlation with RWC, WUE_G, WUE_B, plant height, shoot fresh and dry weight, grain number/main spike, kernel weight and harvest index.     

水分胁迫条件下高粱叶片的渗透调节及其对气孔导度和蒸腾速率的影响

两个抗旱性不同的高粱品种“3197B”和“三尺三”,在水分胁迫条件下,抗旱品种3197B渗透势降低,渗透调节能力较强.正常灌水时,两品种的气孔导度和蒸腾速率均随光照增强而增加,品种间差异不大;水分胁迫条件下,上午3197B气孔导度和蒸腾速率高于三尺三,午后水分胁迫严重时又低于三尺三,但其叶水势和膨压比三尺三高.     

Investigation of Factors Determining Genotypic Differences in Seed Yield of Non-irrigated and Irrigated Chickpeas Using a Physiological Model of Yield Determination

Physiological attributes determining yield, both under drought and under irrigated conditions, of some advanced chickpea lines of recent origin were investigated over two seasons using a physiological model. Total shoot biomass, grain yield, and vegetative (D_v) and reproductive (D_r) durations were measured and the crop growth rates (C) and the rate of partitioning to seed (p) were estimated. The contribution of model parameters to variations in grain yield were determined by path analysis, and the relationships of the yield determinants with seed yield were obtained by regression techniques. The model was found to be suitable for chickpea, and when the parameters were fitted the model explained 98% of the variation. Irrigation enhanced D_r and C. While C was the major single yield determinant, the combination of C and p in non-irrigated environments explained most of the grain yield variation. D_v and D_r exhibited a negative relationship while C and p exhibited a positive relationship under drought stress and a negative relationship in the irrigated environment. There were indications of the existence of an optimum D_v for maximum C among the genotypes, suggesting the need to select for optimum duration genotypes. As high values for p and C in severe drought stress and D_r and C in the irrigated environments are advantageous for high yield, separate breeding strategies are needed for different soil water environments.     

Effect of Mulch from Selected Multipurpose Trees (MPTs) on Growth, Nitrogen Nutrition and Yield of Maize (Zea mays L.)

Leaf extracts and mulch from 14 multipurpose trees were used to test their effects on maize germination, growth and yield. Maize germination was significantly reduced by leaf extracts of all species with increasing extract concentration. The most drastic reductions were caused by Gliricidia sepium , Tetrapleura tetraptera , Lonchocarpus sireceus , Senna siamea and Leucaena leucocephala . Terminalia superba , Tetrapleura tetraptera , Pithecelobium dulce , Gliricidia sepium and Senna siamea significantly reduced maize root growth at the lowest extract concentration, while shoot length was most significantly reduced by Gliricidia sepium , Leucaena leucocephala , Alchornea coordifolia , Pithecelobium dulce , Terminalia superba , and Tetrapleura tetraptera at all concentrations. Growth of maize in pots and yield in the field were controlled by nitrogen supply and uptake. Fast-decomposing leaf material rich in nitrogen promoted growth and yield of maize. Thus Leucaena leucocephala and Gliricidia sepium , both nitrogen-fixing legumes with high nitrogen contents and fast-decomposing leaf materials, significantly increased maize growth and yield. This suggests that the negative effects of leaf extracts observed in the laboratory are ecologically irrelevant in the field.     

Non-destructive Limits to Seed Growth and Leaf Protease Activities in Nodulating and Non-nodulating Soybean Isolines

Leaf senescence leads to a progressive decline in the photosynthetic competence of the leaf. This paper describes some effects of source:sink imbalance on leaf protein catabolism and senescence in soybean. We manipulated pod growth by restricting 100 or 50 % (PR-100 or PR-50, respectively) of young pods at the R4 stage in plastic drinking straws. This effectively reduces final seed mass without interrupting the vascular connections of pods. Nodulating (NOD+) and non-nodulating (NOD−) isolines of the 'Clay' soybean were grown in drainage lysimeters and three pod-restriction (PR) treatments were compared. Pod restriction decreased seed biomass per plant as a result of lower individual seed mass, which was only partially balanced by the increase in seed number. The nitrogen concentration in seeds remained unchanged in NOD+ plants, while it increased with the degree of sink restriction in seeds of NOD− plants. Leaf soluble protein, CO₂ exchange rate and seed nitrogen content were consistently lower in NOD− plants; the leaf protein level remained stable with time in PR-100 plants, decreased for PR-50 and dropped for controls. Endoprotease (HBase) and carboxypeptidase (CPase) activities were significantly lower in leaves from PR-100 plants, while aminopeptidase activity was enhanced, indicating a de novo synthesis of leaf protein. This is consistent with the reported accumulation of vegetative storage proteins (VSPs) in soybean and other legumes after moderate or severe sink reduction. Thus, small modifications of the source:sink ratio such as those obtained by the non-destructive PR technique have an impact on leaf protein catabolism. Nodulating and non-nodulating soybean isolines showed similar responses to PR in terms of leaf senescence initiation and progression, but the rate of the processes appear to be largely influenced by plant N status.     

Effects of Stem-Injected Plant Growth Regulators, with or without Sucrose, on Grain Production, Biomass and Photosynthetic Activity of Field-Grown Corn Plants

Study of plant growth regulators (PGRs) through conventional foliar application or tissue culture or other organic materials has limitations. No previous study has examined the effects of long-term continuous addition of PGRs, with or without sucrose, to field-grown corn ( Zea mays L.) plants. A field study was conducted to determine the effects on corn plant growth and productivity during the grain-filling period of a continuous supply of PGRs, with or without sucrose, using a recently developed injection technique to deliver pressurized solutions through syringe needles sealed to the stem with latex. Our four PGRs (IAA, ABA, ethephon and salicylic acid) and a distilled water control, and two levels of sucrose (150 g l⁻¹ and a distilled water control) were injected into corn plants for 42 consecutive days during the grain-filling period. The plants injected with solutions not containing sucrose took up 42 ml more than those injected with sucrose-containing solutions. Corn plants injected with salicylic acid (SA) produced 9 % more grain yield than plants injected with no PGRs. The combination of SA and sucrose increased the photosynthetic rate by 42 % when compared with distilled water. Injection of ethephon resulted in an 11 % reduction in grain yield. Neither IAA nor ABA altered plant photosynthesis or productivity. Sucrose injection increased the dry weight of injected internodes and stover, and induced partial stomatal closure, although without any measurable effect on net photosynthetic rate. This study showed that stem injection makes possible the study of changes in plant physiology during grain-filling due to the effects of PGRs and metabolites administered continuously over protracted periods of time. It also demonstrated a previously undocumented stimulation of plant photosynthesis and grain yield by SA.     

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.     

Differential Response of Two Wheat Genotypes to Nitrogen Supply. I. Ontogenic Changes in Laminae Growth and Photosynthesis

Two wheat genotypes viz. Uniculm 'gigas' (VI) and Kalyansona (V2) were raised till maturity with low (N1) and adequate (N2) nitrogen levels supplied at 30 and 120kg ha⁻¹, respectively. Laminae, numbering 1–8 on the main shoot, were examined for various parameters at weekly intervals from emergence through senescence. N1 resulted in gradual reduction in laminae growth from 5th leaf onwards with maximum effect on flag and penultimate laminae of both the genotypes. Chlorophyll concentration, soluble protein, rubisco concentration and rubisco activity in response to low N supply was reduced in the top two laminae in V2. Pn rate varied little with leaf position in wheat at adequate N supply. In V2, low N supply resulted in the reduction of laminae N content by about 25% with corresponding reduction in Pn rates in the penultimate and flag laminae. VI, in contrast, exhibited no significant change in leaf N concentration and hence maintained similar Pn rates at both levels of N supply throughout the ontogeny.
It is concluded that the two genotypes responded differently to N supply in relation to laminae growth and photosynthesis. Uniculm 'Gigas' (VI) responded to low N with large reduction in laminae size, adequately maintaining the metabolic constituents such as chlorophyll, soluble protein, rubisco and laminae N concentration and Kalyansona (V2), in contrast, responded with small changes in laminae size and greater reduction in synthesis and maintenance of the metabolic constituents.     

Water Relations and Transpiration of Quinoa (Chenopodium quinoa Willd.) Under Salinity and Soil Drying

Drought and salinity are the two major factors limiting crop growth and production in arid and semi‐arid regions. The separate and combined effects of salinity and progressive drought in quinoa (Chenopodium quinoa Willd.) were studied in a greenhouse experiment. Stomatal conductance (g_s), leaf water potential (Ψ_l), shoot and root abscisic acid concentration ([ABA]) and transpiration rate were measured in full irrigation (FI; around 95 % of water holding capacity (WHC)) and progressive drought (PD) treatments using the irrigation water with five salinity levels (0, 10, 20, 30 and 40 dS m^?1); the treatments are referred to as FI₀, FI₁₀, FI₂₀, FI₃₀, FI₄₀; PD₀, PD₁₀, PD₂₀, PD₃₀, PD₄₀, respectively. The measurements were carried out over 9 days of continuous drought. The results showed that increasing salinity levels decreased the total soil water potential (Ψ_T) and consequently decreased g_s and Ψ_l values in both FI and PD. During the drought period, the xylem [ABA] extracted from the shoots increased faster than that extracted from the roots. A reduction in Ψ_T, caused by salinity and soil drying, reduced transpiration and increased apparent root resistance (R) to water uptake, especially in PD₀ and PD₄₀ during the last days of the drought period. The reasons for the increase in apparent root resistance are discussed. At the end of the drought period, the minimum value of relative available soil water (RAW) was reached in PD₀. Under non‐saline conditions, Ψ_l decreased sharply when RAW reached 0.42 or lower, but under the saline conditions of PD₁₀ and PD₂₀, the threshold values of RAW were 0.67 and 0.96, respectively. In conclusion, due to the additive effect of osmotic and matric potential during soil drying on soil water availability, quinoa should be re‐irrigated at higher RAW in salt‐affected soils, i.e. before the soil water content reaches the critical threshold level causing the drop in Ψ_l resulting in stomatal closure.     

Oxidative Stress and Antioxidants in Wheat Genotypes: Possible Mechanism of Water Stress Tolerance

The role of plant antioxidant systems in water stress tolerance was studied in three contrasting wheat genotypes. Water stress imposed at different stages after anthesis resulted in an increase in lipid peroxidation and a decrease in membrane stability and chlorophyll and carotenoid contents. The antioxidant enzymes ascorbate peroxidase, glutathione reductase and non-specific peroxidase also increased significantly under water stress. Genotype PBW 175, which had highest ascorbate peroxidase, glutathione reductase and peroxidase activity, had the lowest lipid peroxidation (malondialdehyde content) and highest membrane stability and contents of chlorophyll and carotenoids under water stress, while the susceptible genotype WH 542 exhibited the lowest antioxidant enzyme activity, membrane stability and contents of chlorophyll and carotenoids and the highest lipid peroxidation. Genotype HD 2402 showed intermediate behaviour. It seems that drought tolerance of PBW 175, as represented by higher membrane stability and chlorophyll and carotenoid contents and lower lipid peroxidation, is related to its higher antioxidant enzyme activity.     

Relationship between Prehardening, Photosynthetic Activity at Cold Acclimation Temperatures and Frost Tolerance in Winter Rape (Brassica napus var. oleifera). The Consequences for the Reliability of Frost Resistance Estimation under Controlled Conditions

The effect of prehardening (early stage of growth at moderate low temperatures (+12°C) during the day) on the reliability of frost resistance estimation in a controlled environment has been studied on three winter oilseed rape cultivars differing markedly in their field survival rate (Leo, Górczański and Idol). It has been also examined the relationship between the photosynthetic activity during the first stage of cold acclimation and the level of frost resistance observed in investigated cultivars. Presented results demonstrated that prehardening, which increases to a significant degree the effectiveness of the cold acclimation process, also increases the differences in cold hardiness between cultivars, and limits the magnitude of experimental errors made during frost resistance estimation under controlled conditions. In all studied cultivars, prehardening increases significantly the photosynthetic activity during cold acclimation. On the other hand, both in the prehardened and in the non-prehardened plants, no relation has been found between either gas exchange rates or chlorophyll 'a' fluorescence characteristics at low temperatures and cultivar ability for acclimation. Neither the existing differences in photosynthetic activity, nor the degree of photosynthetic apparatus acclimation to cold, which occurs during prehardening, are the factors responsible for the frost resistance variation observed between studied cultivars.     

Response of Mustard (Brassica juncea L.) to Applied Nitrogen with or without Ethrel Spray under Non-irrigated Conditions

Field studies were conducted during the winter seasons of 1995–96 and 1996–97 at the Agricultural Farm of Aligarh Muslim University, Aligarh, India on mustard ( Brassica juncea L. Czern & Coss., var. Alankar) under non-irrigated conditions, to evaluate the effect of foliar spray of 200 p.p.m. ethrel (2-chloroethyl phosphonic acid) at flowering growth stage along with basal 0, 40, 80 or 120 kg N ha⁻¹ on net photosynthetic rate (P_N), stomatal conductance (C_S), stomatal resistance (R_S), leaf K content, relative water content (RWC), leaf area index (LAI) and total dry matter (TDM) production monitored at 20 days after spray application, and plant N content, seed N content, nitrogen harvest index (NHI), nitrogen yield merit (NYM), pods plant⁻¹, 1000 seed weight, seed yield, biological yield, harvest index (HI), seed yield merit (SYM) and merit of genotype (MOG) at harvest. Results indicated that, at 0 or 40 kg N ha⁻¹, ethrel did not produce any significance effect, but at basal 80 kg N ha⁻¹, ethrel affected the parameters favourably with the exception of 1000 seed weight, HI, seed N and NHI. Ethrel-sprayed plants utilized N from the soil more effectively and showed increased NYM. Yield attributes, seed yield and merit of genotype (in terms of NYM and SYM) were also enhanced. Ethrel spray enhanced seed yield under water stress conditions mainly by increasing K uptake and retaining higher RWC, thereby decreasing R_S and increasing LAI, P_N and TDM production.     

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.     

Effects of Chemical Ameliorants on Stomatal Frequency and Water Relations in Brinjal (Solanum melongena L.) under Moisture Stress Conditions

A study was conducted to investigate the effects of three chemical ameliorants, namely, cycocel, limewash and potassium chloride, on stomatal frequency, leaf water potential and relative water content in brinjal ( Solanum melongena L.) plants under moisture stress conditions. Moisture stress imposed at three stages decreased stomatal frequency, the length and breadth of stomata, leaf water potential and relative water content. Of the chemical ameliorants investigated, potassium chloride performed best in terms of stomatal behaviour and leaf water potential, whereas cycocel proved best in the case of relative water content.