Effect of abscisic acid on the transport of assimilates in barley

The effect of abscisic acid (ABA) on assimilate transport in barley was investigated in two parallel experiments. First, the effect upon [¹⁴C]sucrose transport from the flag leaf to the ear of a single ABA application made at different stages of growth of the fruits was investigated; the effect was measured 24 h after treatment. Second, the effect of a single application of ABA made at the same stages of growth as above on grain weight of the mature plant was investigated. In both types of experiments ABA was applied once to the ear of different plants as an aqueous solution (10^-3–10^-5 M), one to five weeks after anthesis. [¹⁴C] sucrose was applied by means of agar blocks. Parallel to these experiments, the endogenous content of ABA was investigated in the developing grains. When ears were treated with ABA two or four weeks after anthesis, an increase of up to 70% in the ¹⁴C-transport from the flag leaf to the ear was observed within a 24-h period after treatment (short duration experiments). At these growth stages the endogenous concentrations of ABA were low. In sharp contrast, ABA, especially in a concentration of 10^-3 M, decreased ¹⁴C-import from the flag leaf when applied three weeks after anthesis. At this stage the endogenous ABA content had reached its maximum. Long duration experiments with a single application of ABA to the car two weeks after anthesis resulted in a marked increase of weight per thousand kernels. ABA applications made earlier or later than two weeks after anthesis either reduced the grain weight or had no effect. It is concluded that ABA is involved in the regulation of assimilate transport from the leaves to the grains, possibly by influencing the unloading of sieve tubes in the ears. Promotion or inhibition of assimilate import by exogenously applied ABA may depend on the developmental stage of the grains and on the endogenous ABA level.Abbreviations ABA abscisic acid - TKW weight per thousand kernels     

Exogenous ABA Increases Yield in Field-Grown Wheat with Moderate Water Restriction

Water stress is one of the most important environmental factors that regulate a plant’s growth and development. In agronomic practice the effects of water stress are translated into low yield and/or reduced quality. Abscisic acid (ABA) sprays (1 mM) were applied to wheat plants at different phenological stages and the effects on several physiological variables and on yield were evaluated under field conditions at different water regimes. Studies were conducted in the field across three consecutive winter–spring seasons. ABA treatments were applied at the beginning of shoot enlargement and repeated at anthesis. Exogenous ABA increased shoot dry weight and maintained a high concentration of photosynthetic pigments for a longer period of time during grain growth and maturation. Although ABA applications increased stomatal closure immediately after its application, the longer-term effect was to allow for a greater ostiolar opening of the stomatal pore which resulted in increased conductance of gases and water vapor. ABA also improved the transport of photoassimilates from the leaves and stem to the developing grains, that is, it effectively increased the sink strength of the grains. This correlated with a yield increase without significantly changing the protein quality in the grains. Thus, elevated ABA levels from exogenous application or genetic selection could help improve agricultural production of grains in arid areas where irrigation is not possible.     

氮素形态对小麦花后不同器官内源激素含量的影响

采用盆栽方法,研究了酰胺态氮、铵态氮和硝态氮对小麦(Triticum aestivum)花后根系、旗叶和籽粒内源激素IAA、GA₃、ABA和ZR含量的影响。结果表明,小麦不同器官的内源激素含量对3种氮素形态的响应不同。氮素形态调节籽粒灌浆是通过根系、旗叶和籽粒中内源激素的协同作用而实现的。酰胺态氮与硝态氮处理相比,小麦花后5~15 d,旗叶GA₃含量、籽粒IAA和ABA含量较高,籽粒灌浆速率(Grain-filling rate, GFR)较高;花后15~25 d,根系GA₃含量、旗叶IAA和GA₃含量、籽粒ABA含量较高,籽粒IAA含量较低,GFR较低。铵态氮与硝态氮处理相比,小麦花后5 d,籽粒ZR含量较高;花后15 d前后,籽粒IAA、ABA含量较低,GFR较低;花后20~25 d,根系ZR、GA₃含量较低,旗叶IAA、GA₃含量较低,ABA含量较高,籽粒ABA、GA₃含量较低,IAA含量较高,GFR较高。铵态氮比硝态氮处理的小麦籽粒粒重显著增加。铵态氮和酰胺态氮处理比硝态氮处理增产显著。建议在‘豫麦49’施肥时,使用铵态氮或酰胺态氮并配施硝化抑制剂。     

Abscisic acid added to the nutrient solution induces a water deficit-like response in Trifolium subterraneum

The response of subterranean clover (Trifolium subterraneum) to the addition of increasing concentrations of abscisic acid (ABA) in the nutrient solution (10^?3, 10^?2 and 10^?1 mol m^?3) was studied under growth room conditions. Six cultivars of contrasting yield capacity were compared. Plants were grown in Hoagland's solution until they had produced at least four fully developed leaves. ABA was then added and its effect on the fresh weight, leaf number and longest root length was determined, 1 day, 4 days, 7 days and 11 days after addition. The addition of ABA caused significant reductions in all the measured growth parameters, as well as a significant decrease in leaf water potential, which was dependent on the ABA concentration. The average growth reduction after 11 days under 10^?1 mol m^?3 ABA were within previously reported ranges for this crop under drought, in field conditions. The average leaf number, area of a fully developed leaf and the dry weight per plant of the six cultivars decreased by approximately 50%, whereas the root/shoot ratio increased by 80%. The variation and ranking for this treatment resembled closely those obtained for the same cultivars in field experiments. The cvs Clare, Nuba and Seaton Park, showed the best results under both control and ABA treated conditions. The correlation between the response to ABA in nutrient solution and previous water deficit studies raises the possibility of using this approach as an alternative way to quantify the drought sensitivity of subterranean clover cultivars.     

RFLP mapping of quantitative trait loci controlling abscisic acid concentration in leaves of drought-stressed maize (Zea mays L.)

 Abscisic acid (ABA) concentration in leaves of drought-stressed plants is a quantitatively inherited trait. In order to identify quantitative trait loci (QTLs) controlling leaf ABA concentration (L-ABA) in maize, leaf samples were collected from 80 F_3:4 families of the cross Os420 (high L-ABA)×IABO78 (low L-ABA) tested under drought conditions in field trials conducted over 2 years. In each year, leaf samples were collected at stem elongation and near anthesis. The genetic map obtained with 106 restriction fragment length polymorphism (RFLP) loci covered 1370 cM, which represented approximately 85% of the UMC maize map. Sixteen different QTLs with a LOD>2.0 were revealed in at least one sampling. Across samplings, only four QTLs significantly influenced L-ABA, accounting for 66% of the phenotypic variation and 76% of the genetic variation among families. At these QTLs, the alleles which increased L-ABA were contributed by Os420. The two most important QTLs were mapped on chromosome 2 near csu133 and csu109a. The effects associated with the QTL near csu133 were more pronounced near anthesis. The support intervals of the four primary QTLs for L-ABA did not overlap the presumed map position of mutants impaired in ABA biosynthesis. Received: 27 January 1998 / Accepted: 22 April 1998     

Growth, light interception and yield responses of spring wheat (Triticum aestivum L.) grown under elevated CO2 and O3 in open-top chambers

Spring wheat cv. Minaret was grown to maturity under three carbon dioxide (CO₂) and two ozone (O₃) concentrations in open-top chambers (OTC). Green leaf area index (LAI) was increased by elevated CO₂ under ambient O₃ conditions as a direct result of increases in tillering, rather than individual leaf areas. Yellow LAI was also greater in the 550 and 680 μmol mol^–1 CO₂ treatments than in the chambered ambient control; individual leaves on the main shoot senesced more rapidly under 550 μmol mol^–1 CO₂, but senescence was delayed at 680 μmol mol^–1 CO₂. Fractional light interception (f) during the vegetative period was up to 26% greater under 680 μmol mol^–1 CO₂ than in the control treatment, but seasonal accumulated intercepted radiation was only increased by 8%. As a result of greater carbon assimilation during canopy development, plants grown under elevated CO₂ were taller at anthesis and stem and ear biomass were 27 and 16% greater than in control plants. At maturity, yield was 30% greater in the 680 μmol mol^–1 CO₂ treatment, due to a combination of increases in the number of ears per m^–2, grain number per ear and individual grain weight (IGW). Exposure to a seasonal mean (7 h d^–1) of 84 nmol mol^–1 O₃ under ambient CO₂ decreased green LAI and increased yellow LAI, thereby reducing both f and accumulated intercepted radiation by ≈ 16%. Individual leaves senesced completely 7–28 days earlier than in control plants. At anthesis, the plants were shorter than controls and exhibited reductions in stem and ear biomass of 15 and 23%. Grain yield at maturity was decreased by 30% due to a combination of reductions in ear number m^–2, the numbers of grains per spikelet and per ear and IGW. The presence of elevated CO₂ reduced the rate of O₃-induced leaf senescence and resulted in the maintenance of a higher green LAI during vegetative growth under ambient CO₂ conditions. Grain yields at maturity were nevertheless lower than those obtained in the corresponding elevated CO₂ treatments in the absence of elevated O₃. Thus, although the presence of elevated CO₂ reduced the damaging impact of ozone on radiation interception and vegetative growth, substantial yield losses were nevertheless induced. These data suggest that spring wheat may be susceptible to O₃-induced injury during anthesis irrespective of the atmospheric CO₂ concentration. Possible deleterious mechanisms operating through effects on pollen viability, seed set and the duration of grain filling are discussed.     

ATPase activity in plasmalemma-rich vesicles isolated by aqueous two-phase partitioning from Vicia faba mesophyll and epidermis: Characterization and influence of abscisic acid and fusicoccin

Plasmalemma-rich microsomal vesicles were prepared from whole leaf and acid-washed epidermal tissue of Vicia faba L. cv. Osnabrücker Markt by aqueous two-phase partitioning in dextran T-500 and polyethylenglycol 1350 aqueous phases. These vesicles were tightly sealed and predominantly right-side out, and contained a K⁺ -stimulated, mg²⁺-dependent and vanadate-sensitive ATPase. The enzyme from both tissues exhibited nearly identical properties: pH optimum 6.4, K_m for ATP 0.60 mM(whole leaf) and 0.67 mM (epidermis). V_max -480 nmol (mg protein)¹ min¹ (whole leaf) and 510 nmol (mg protein)¹ min¹ (epidermis), I₅₀ (Na₃,VO₄) 7.5 μM (whole leaf) and 15 μM (epidermis). The enzyme was not inhibited by NO₃(50 mM)or sodium azide (I mM). DCCD (20 μM) reduced enzyme activity to 50% (whole leaf) and 58% (epidermis), gramicidin S (20 μM) to 36% (whole leaf) and 41%(epidermis). Ca²⁺ inhibited the ATPase [I₅₀, C²⁺: 0.5 mM(whole leaf) and 0.8 mM(epidermis)]. Ca²⁺ inhibited the ATPase [I₅₀, C²⁺ 0.5 mM(whole leaf) und 0.8 (epidermis)]. The vanadate-sensitive ATPase from whole leaf and epidermal tissue was slightly but significantly stimulated by fusicoccin (FC) at a concentration (0.13 μM) promoting stomatal opening. The stimulation was not seen in the solubilized ATPase. Stomata of the cultivar used here were insensitive lo (±)ABA up to 2 μM level which is effective in most other cultivars and species. Likewise, at this concentration no effect of ABA on the activity of the epidermal ATPase was observed. The data are discussed with respect to the interaction of FC and ABA with the ATPase.     

Grain Yield in Pearl Millet in Relation to Source Size and Proximity to Sink

Two pearl millet [Pennisetum glaucum (L.) R. Br. emend. Stuntz] hybrids GHB-30 and MH-179 were given defoliation treatments prior to anthesis comprising zero leaf to intact control. Keeping or removing even flag leaf only significantly altered the grain yield. With increasing leaf area (leaf numbers) the grain yield also significantly increased. Test mass showed more or less a similar trend. The leaves in the upper portion (nearer to sink) showed a greater contribution to the grain yield than the lower ones (away from sink). However, the highest leaf efficiency in terms of contribution per unit leaf area and the contribution by the whole leaf to the grain yield was recorded by 4^th and 3^rd leaf, respectively. The stem (covered with petioles) contributed to the extent of around 12 %. The existing leaves compensated to some extent for the defoliated ones.     

Physiological and yield responses of recombinant chromosome substitution lines of barley to terminal drought in a Mediterranean‐type environment

Physiological traits and productivity of the recombinant chromosome substitution lines (RCSLs) of barley, developed through the cross of Hordeum vulgare ssp. vulgare cv. Harrington and the wild ancestor Hordeum vulgare ssp. spontaneum, were measured in plants growing in microplots (with and without irrigation) and in field conditions in two Mediterranean‐type environments, Cauquenes (rainfed) and Santa Rosa (irrigated). The objectives were to assess the degree of phenotypic variability in response to terminal drought stress and to test whether the introgression of the wild ancestor into cv. Harrington can increase the terminal drought tolerance of RCSLs of barley. Days from emergence to anthesis and from anthesis to maturity of the 80 RCSLs were reduced in only 2–4 days under water stress, in microplots. Specific leaf area (SLA) and stomatal conductance (gs) of 80 RCSLs and cv. Harrington decreased greatly under water stress in plants growing in microplots and field conditions (in 2004/05 growing season). No G × E interaction was detected except for SLA in the microplot experiment. The principal component analysis provided a clear distinction between RCSLs. Along the first principal component, it was possible to identify 24 RCSLs which represent the whole range of grain yield (GY), gs and SLA observed in the 80 RCSLs. The selected 24 RCSLs were evaluated in field conditions at Cauquenes and Santa Rosa, during two growing seasons (2007/08 and 2008/09). The gs and carbon isotope discrimination in grains (Δ¹³C) were significantly (P < 0.001) lower in the rainfed condition (Cauquenes), but the water‐soluble carbohydrates (WSC) in stems at anthesis and maturity was significantly (P < 0.001) higher than in well‐irrigated condition (Santa Rosa). Grain yield was reduced by 63% under drought conditions. Differences between RCSLs in gs, WSC and GY were significant (P < 0.001) in 2007/08. The stress tolerance index (STI) was highly (P < 0.01) correlated with GY in all environments (rainfed and irrigated conditions and the two growing seasons). The relationship between STI and Δ¹³C under rainfed condition allowed identifying drought tolerant and susceptible RCSLs; the former were high yielding lines under rainfed and irrigated conditions (and higher STI values), but with similar GY to cv. Harrington, but presented higher grain Δ¹³C values than cv. Harrington. The drought susceptible lines presented lower GY, STI and Δ¹³C values than cv. Harrington. These results suggest that H. spontaneum has contributed alleles that increase terminal drought tolerance to some of the RCSLs.     

Impact of the TaMATE1B gene on above and below-ground growth of durum wheat grown on an acid and Al3+-toxic soil

Background and aims

Subsoil acidity with a high aluminium (Al³⁺) soil content inhibits root growth and proliferation of durum wheat (tetraploid AABB, Triticum turgidum) leading to poor nutrient and water uptake. This study evaluated the impact of Al³⁺-tolerantTaMATE1B allele on root and shoot traits of durum wheat grown in an acidic soil with a high Al³⁺concentration.

Methods

Two durum wheat lines, Jandaroi–TaMATE1B with the TaMATE1B gene introgressed from Al³⁺-tolerant bread wheat and Jandaroi–null (a sister line lacking the Al³⁺-tolerant TaMATE1B allele), were grown in rhizoboxes in a glasshouse. We mapped root growth and proliferation over time and measured shoot traits and grain yield.

Results

Introgression of the Al³⁺-tolerant TaMATE1B allele into durum wheat enabled root growth and proliferation below 0.25 m of the soil profile, where the soil pH was low (4.1, CaCl₂ extract) with high Al³⁺ content (16.5 mg kg⁻¹), and increased total root length and biomass at 42 days after sowing (DAS; Z₃₃) by 38.3 and 22%, respectively, relative to the Jandaroi–null. Differences in root growth between the two lines were apparent from tillering stage (Z₃₃) and by 50% anthesis (Z₆₄), respectively. Jandaroi–TaMATE1B had 69.2% greater root biomass, 76.2% greater root length, 5.89% greater leaf area and 18% greater shoot biomass than Jandaroi–null at 50% anthesis (Z₆₄). Time to anthesis and physiological maturity was delayed 6–7 days in Jandaroi–TaMATE1B, compared to Jandaroi–null. Jandaroi–TaMATE1B tended to have relatively greater, but not significantly different, shoot biomass, grain yield and yield components than Jandaroi–null.

Conclusions

Introgression of the Al³⁺-tolerant TaMATE1B allele into durum wheat enabled root growth and proliferation down an acidic soil profile with a high Al³⁺ concentration. We assume that in the field where plants need to acquire water at depth differences in above-ground parameters would be amplified.

     

Effects of the deficiens allele on ear development and yield in barley

Lines partially-isogenic for the deficiens (V^tV^t and two-rowed (VV) barley ear types were developed in the genetic background of cv. Kym, for comparisons of ear development and yield components. The suppression of lateral floret growth by the V^t allele during pre-anthesis ear development occurred at a relatively late stage and only occasionally was median floret survival enhanced in the deficiens line. The final size of lateral florets in both deficiens and normal ear types appeared to be largely governed by assimilate supply. At anthesis, the lateral florets comprised about 10% of the dry matter of normal ears, whereas in the deficiens ears the median florets were correspondingly heavier. After anthesis, grain growth in the deficiens line was slower than in the normal line, although final grain weight was not affected. In another experiment the V^t allele occasionally increased the number of grains per ear, but consistently decreased the weight per grain. In drilled plot trials, the mean yield of the deficiens line was 8% lower than the normal. Excision of lateral florets at anthesis showed that photosynthesis in these organs did not contribute to the yield advantage of the normal ear type. It is suggested that the inferior performance of the deficiens type was attributable to the greater physical constriction of endosperm expansion imposed by the development of thicker, more rigid, palea and lemma tissues.     

Does an antagonistic relationship between ABA and ethylene mediate shoot growth when tomato (Lycopersicon esculentum Mill.) plants encounter compacted soil?

This study tested the hypothesis that antagonistic interactions between abscisic acid (ABA) and ethylene mediate the effects of soil compaction on shoot growth. Isogenic wild‐type (Ailsa Craig), ABA‐deficient (notabilis) and a transgenic (ACO1_AS) tomato genotype with a reduced capacity to synthesize ethylene were examined. Exogenous ABA was also applied. Leaf area was comparable when Ailsa Craig and ACO1_AS were grown in uncompacted (1·1 g cm^?3) or compacted (1·5 g cm^?3) soil, but was lower in notabilis. However, a 1·1/1·5 g cm^?3 split‐pot treatment invoked marked genotypic differences, whereby leaf area was comparable to 1·1 g cm^?3 control plants in ACO1_AS but was intermediate between the 1·1 and 1·5 g cm^?3 treatments in Ailsa Craig and notabilis. ABA may be discounted as the root‐sourced signal responsible for reducing leaf area when the roots encountered compacted soil as Ailsa Craig and ACO1_AS showed differing responses despite similar increases in xylem sap ABA concentration; leaf area was invariably lower in notabilis. These genotypic differences were correlated with ethylene evolution; thus the greater leaf area in ACO1_AS was associated with its reduced ability to synthesize ethylene, whereas the reductions in leaf expansion observed when Ailsa Craig and notabilis encountered compacted soil were accompanied by increased ethylene production. Application of ABA had little effect on ACO1_AS, but promoted a recovery of leaf expansion in notabilis, and more surprisingly in Ailsa Craig. These results suggest that antagonistic interactions between ABA and ethylene may regulate leaf expansion when the root system simultaneously encounters uncompacted and compacted soil.     

Effect of triacontanol and chlormequat on growth,plant hormones and artemisinin yield in Artemisia annua L.

Artemisinin and herbage yield of Artemisia annua plants were determined after application of triacontanol (tria.) and chlormequat (2-chloroethyltrimethylammonium chloride). Tria. at 1.0 and 1.5 mgl^–1 produced a statistically significant positive effect on artemisinin level as well as on plant height, leaf and herbage yield. Chlormequat at 1000 and 1500 mgl^–1 also increased artemisinin level, decreased the plant height at higher concentrations and increased the leaf and herbage yield at lower concentrations. Tria. application enhanced GA-like activity, but ABA levels decreased, while chlormequat increased ABA but reduced GA-like substances. The effect of Tria. on artemisinin yield seems to be mediated through its effect on plant growth.CIMAP Publication.     

Nitrogen Metabolism of the Upper Three Leaf Blades of Wheat at Different Soil Nitrogen Levels

Upper three leaf blades on the mainshoot of wheat cultivar, cv. Pusa Lerma, grown under three soil nitrogen levels (0, 30 and 120 kg ha^-1), were examined for changes in total reduced nitrogen and protease activity at pH 4.0 and 7.0. No net loss of reduced nitrogen takes place prior to and around anthesis. The protease activity is low during this period. At later stages there is rise in the loss of nitrogen which is paralleled by enhancement in protease activity. From amongst the leaf blades, nitrogen concentration is significantly high in the flag and penultimate as compared to the values in the third leaf blade. There were significant differences in protease activity (pH 4.0) amongst the leaf blades. At pH 7.0, however, the differences between the flag and penultimate leaf blades were not significant. Highest enzyme activity was in the flag followed by penultimate and then third leaf blade. Soil N application significantly enhanced the nitrogen content of all the leaf blades. At pH 4.0, the protease activity (g fr. wt.^-1) increased significantly due to soil N application (N₃₀ over N₀). There was, however, decline in the enzyme activity at pH 7.0, though the differences at different soil N levels were not significant. Analysis in terms of μmol N (reduced form) accumulated in the grains (ear)^-1 revealed that two-thirds of N is translocated by 28-day stage and the rest between 28-day and final harvest. The three leaf blades together contributed 22.7, 32.6 and 48.5% of the grain N (ear)^-1 at N₀, N₃₀ and N₁₂₀- respectively. Most of the nitrogen applied to the soil is reduced by these leaf blades.     

Effects of early-fruit removal on endogenous cytokinins and abscisic acid in relation to leaf senescence in cotton

Numerous studies have shown that early-fruit removal enhances vegetative growth and development of cotton (Gossypium hirsutum L.). However, few studies have examined changes in leaf senescence and endogenous hormones due to fruit removal. The objective of this study was to determine the correlation between some endogenous phytohormones, particularly the cytokinins and abscisic acid (ABA), and leaf senescence following fruit removal. Cotton was grown in pots and in the field during 2005 and 2006. Two early-fruiting branches were excised from plants at squaring to form the fruit removal treatment while the non-excised plants served as control. Plant biomass, seed cotton yield, cytokinins and ABA levels in main-stem leaves and xylem sap as well as main-stem leaf photosynthetic rate (Pn) and chlorophyll (Chl) concentration were determined after removal or at harvest. Fruit removals increased the leaf area, root and shoot dry weight and plant biomass at 35 days after removal (DAR), whether in potted or field-grown cotton; under field conditions, it also improved plant biomass and seed cotton yield at harvest. The Pn and Chl concentration in excised plants were significantly higher than in control plants from 5 to 35 DAR, suggesting that fruit removal considerably delayed leaf senescence. Fruit-excised plants contained more trans-zeatin and its riboside (t-Z + t-ZR), dihydrozeatin and its riboside (DHZ + DHZR), and isopentenyladenine and its riboside (iP + iPA) but less ABA in both main-stem leaves and xylem sap than control plants from 5 to 35 DAR. These results suggest that removal of early fruiting branches delays main-stem leaf senescence, which can be attributed to increased cytokinin and/or reduced ABA. Cytokinin and ABA are involved in leaf senescence following early fruit removal.     

Nitrogen Translocation in Wheat Plants Under Soil Water Deficit

Accumulation and translocation of nitrogen (N) in the vegetative organs and grains of winter wheat (Triticum aestivum L.) are important processes in determining yield and quality. The present study was conducted to compare the effects of water deficit and cultivars (cv. Lumai 21 and Jinan 17) on N translocation from vegetative organs to grains in a mobile rain-shelter using ¹⁵N-labeled ammonium sulfate fertilizer. The N translocation amounts (defined as the difference between the N amount at anthesis and the N amount at maturity for a vegetative organ) in leaves were greatest for the two cultivars, followed by glumes, stems, and sheaths, respectively. The N translocation ratio (defined as the ratio of the translocation amount to N amount at anthesis) in total above-ground parts were greater for Lumai 21 (0.65 g g⁻¹ DW) than for Jinan 17 (0.60 g g⁻¹ DW), and Lumai 21 plants had a higher N translocation ratio for the N derived from fertilizers. The N contribution (defined as the ratio of the translocation amount to grain N amount) of total vegetative parts aboveground to grain N ranged from 0.50 to 0.77 g g⁻¹ DW, and that of the leaf was the greatest. The results showed that water deficit remarkably increased the N translocation ratio derived from soil and the contributions of N in various vegetative organs to grain N. It is suggested that water deficit would weaken the availability of fertilizer N but enhance the remobilization of prestored N to the grains.     

Alterations in photosynthesis and antioxidant enzyme activity in winter wheat subjected to post-anthesis water-logging

Winter wheat (Triticum aestivum L.) cultivars Yangmai 9 (water-logging tolerant) and Yumai 34 (water-logging sensitive) were subjected to water-logging (WL) from 7 d after anthesis to determine the responses of photosynthesis and anti-oxidative enzyme activities in flag leaf. At 15 d after treatment (DAT), net photosynthetic rate under WL was only 3.7 and 8.9 μmol(CO₂) m⁻² s⁻¹ in Yumai 34 and Yangmai 9, respectively, which was much lower than in the control. Ratios of variable to maximum and variable to initial fluorescence, actual photosynthetic efficiency, and photochemical quenching were much lower, while initial fluorescence and non-photochemical quenching were much higher under WL than in control, indicating damage to photosystem 2. WL decreased activities of superoxide dismutase and catalase in both cultivars, and activity of peroxidase (POD) in Yumai 34, while POD activity in Yangmai 9 was mostly increased. The obvious decrease in the amount of post-anthesis accumulated dry matter, which was redistributed to grains, also contributed to the grain yield loss under WL.     

Abscisic Acid Sprays Significantly Increase Yield per Plant in Vineyard-Grown Wine Grape (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.) cv. Cabernet Sauvignon Through Increased Berry Set with No Negative Effects on Anthocyanin Content and Total Polyphenol Index of Both Juice and Wine

In many cultivars of Vitis vinifera periods of mild water stress during ripening are thought to increase grape quality for winemaking, even though yields may be negatively affected. Because abscisic acid (ABA) is involved in the signaling of water stress in plants, we examine the effects of the ABA signal being given without the concomitant water stress. ABA at 250 mg l⁻¹ was sprayed weekly or biweekly from bud-burst until harvest onto the leaves of vineyard-grown plants of cv. Cabernet Sauvignon. For ABA-treated plants berry yield per bunch and per plant was significantly increased (1.5- to 2.0-fold) across three consecutive harvests (2005 through 2007). Number of berries per bunch and per plant was the primary basis for the significant crop increases, although bunches per plant also tended to increase (1.1- to 1.3-fold) across all three harvests. Other parameters assessed included number of internodes, shoot length, leaf area, leaf water potential at midday, photosynthesis, and stomatal conductance. These parameters showed no significant change with ABA treatment, although shoot length tended to be reduced, as was leaf area relative to control plants. The significantly increased fruit yields were thus accomplished without accompanying increases in leaf photosynthesis and leaf areas. Juice at harvest had equal levels of sugars (Brix) and somewhat higher levels of anthocyanins and total polyphenols relative to control values. The two latter trends continued for the resultant wine across two vintage years. In conclusion, three seasons of experimental trials have demonstrated that ABA application can significantly enhance yield per plant in the field-grown grape (cv. Cabernet Sauvignon) by favoring increased berry set without diminishing the quality of the fruit for winemaking use.     

Interrelationship between Leaf Gas-Exchange Characteristics,Area Leaf Mass,and Yield in Soybean (Glycine max L. Merr) Genotypes

Variability in leaf gas-exchange traits in thirteen soybean (Glycine max L. Merr) genotypes was assessed in a field experiment conducted at high altitude (1 950 m). Leaf net photosynthetic rate (P ^N) exhibited a high degree of variability at all the growth stages studied. P _N and other gas-exchange parameters exhibited a seasonal pattern that was similar for all the genotypes. P _N rate was highest at seed filling stage. P _N was positively and significantly associated with aboveground dry matter and seed yield. The area leaf mass (ALM) exhibited a strong positive association with leaf P _N, aboveground dry matter, and seed yield. The positive association between ALM, P _N, and seed yield suggests that this simple and easy to measure character can be used in breeding programmes as a surrogate for higher photosynthetic efficiency and eventually higher yield.     

Distribution between parts of the main shoot and the tillers of photosynthate produced before and after anthesis in the top three leaves of main shoots of Hobbit and Maris Huntsman winter wheat

The top three leaves of main shoots in crops of Hobbit and Maris Huntsman winter wheat were exposed to ¹⁴CO₂ at 22 and 16 days before and at 10 days after anthesis in 1978. The distribution of the ¹⁴C recovered in whole plants at anthesis and at maturity was measured. There was negligible loss of ¹⁴C between these two times, but some redistribution. The percentage in the tillers was negligible when the flag leaf (leaf 1) was exposed to ¹⁴CO₂, and otherwise less than 12% except for ¹⁴C absorbed by the third leaf at 16 days before anthesis, when it averaged 26% but was very variable. When ¹⁴C was supplied before anthesis, about 20% reached the grain whichever leaf had been supplied. The ear structures contained about 10% of that absorbed by the third leaf and 35% of that absorbed by the flag or second leaf. When ¹⁴C was supplied after anthesis, the amounts reaching the grain from the different leaves were: flag 82%, second 68%, third 56%. Most of the remainder was in the stem. The exposed leaf never retained more than 6%. The amount of ¹⁴C that moved from the stem to the grain between anthesis and maturity was about 50% greater in the semi-dwarf variety Hobbit than in Maris Huntsman. There was no significant varietal difference in the percentage of post-anthesis ¹⁴C reaching the grain. The ear structures of Hobbit contained about a third more ¹⁴C than those of Maris Huntsman. An additional 90 kg N ha^-1, which increased grain yield by 46%, had negligible effects on the distribution of ¹⁴C.