Effects of water-saving superabsorbent polymer on antioxidant enzyme activities and lipid peroxidation in oat (Avena sativa L.) under drought stress

BACKGROUND: Drought stress significantly limits oat (Avena sativa L.) growth and productivity. Thus an efficient management of soil moisture and study of metabolic changes in response to drought are important for improved production of oat. The objective was to gain a better understanding of drought tolerance mechanisms and improve soil water management strategies using water‐saving superabsorbent polymer (SAP) at 60 kg ha^?1 under three irrigation levels (adequate, moderate and deficit) using a new type of hydraulic pressure‐controlled auto irrigator. RESULTS: The results showed that the relative water content and leaf water potential (ψ₁) were much higher in oats treated with SAP. Although the SAP had little effect on plant biomass accumulation under adequate and moderate irrigation, it significantly increased the biomass by 52.7% under deficit irrigation. Plants treated with SAP under deficit irrigation showed a significant decrease in superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and glutathione reductase activities in leaves compared with control plants. CONCLUSION: Our results suggested that drought stress leads to production of oxygen radicals, which results in increased lipid peroxidation and oxidative stress in the plant, and the application of SAP could conserve soil water, making same available to plants for increased biomass accumulation and reduced oxidative stress especially under severe water stress. Copyright © 2010 Society of Chemical Industry     

Effectiveness of a water-saving super-absorbent polymer in soil water conservation for corn (Zea mays L.) based on eco-physiological parameters

BACKGROUND: The objective was to study soil water conservation and physiological growth of corn (Zea mays L.) using water‐saving super‐absorbent polymer (SAP) at 30 kg ha^?1. The effectiveness of SAP was studied under three irrigation levels (adequate, moderate and deficit) using a new type of negative hydraulic pressure controlled auto‐irrigator in the years 2009 and 2010 in a greenhouse at Beijing, P.R. China. RESULTS: Eight weeks after sowing, plant height and leaf area increased significantly by 41.6 and 79.6% under deficit irrigation for SAP treatment. The SAP had little effect on shoot dry mass under adequate and moderate irrigation but increased it significantly by 133.5% under deficit irrigation. Similarly, the efficiency of water use also increased by 97.1%. Leaf water potential under adequate and moderate irrigation differs slightly for SAP application, whereas under deficit irrigation the values were exceeded significantly by 27.8%. The superior growth and water use efficiency of corn treated with SAP under deficit irrigation was ascribed to maintenance of higher relative water contents in leaves as well as intercellular carbon dioxide concentration, net photosynthesis and transpiration rate. CONCLUSIONS: Our results suggested that plant growth and different physiological activities are restricted by drought stress and the application of super‐absorbent polymer could conserve soil water, making same available to plants for increased growth and biomass accumulation especially under severe water stress. Thus, application of SAP is a suitable soil management practice for the locations characterised by severe water stress. Copyright © 2011 Society of Chemical Industry     

A lysimeter study of nitrate leaching, optimum fertilisation rate and growth responses of corn (Zea mays L.) following soil amendment with water-saving super-absorbent polymer

BACKGROUND: Nitrate leaching and the resulting groundwater contamination from intensive cereal production has become a major concern for long‐term farmland efficiency and environmental sustainability in northern China. The aim of this study was to evaluate a water‐saving super‐absorbent polymer (SAP) for minimising NO₃^? leaching from soil and optimising corn growth and yield. Thirty‐six undisturbed soil lysimeters were installed in a field lysimeter facility in drought‐affected northern China to study the growth and yield characteristics of summer corn (Zea mays L.) as well as the amount of NO₃–leaching losses under different fertiliser (standard, medium or 75% and low, or 50% of conventional fertilisation rate) and SAP (control, 0; level‐1, 15 kg ha^?1 and level‐2, 30 kg ha^?1) treatments. RESULTS: Corn yield fell by 19.7% under medium and 37.7% under low fertilisation; the application of SAP increased yield significantly by 44.4% on level‐1 and 80.3% on level‐2. Similarly, plant height, leaf area, number of grains as well as protein, soluble sugar and starch contents in the grain also increased with SAP treatment. Application of SAP at 30 kg ha^?1 plus half of conventional fertilisation can reduce maximum (64.1%) nitrate leaching losses from soil. CONCLUSIONS: Application of SAP at 30 kg ha^?1 plus only half the amount of conventional fertiliser rate (150 kg urea, and 50 kg each of superphosphate and potassium sulfate) would be a more appropriate practice both for minimising nitrate leaching and sustainable corn production under the arid and semiarid conditions of northern China. Copyright © 2011 Society of Chemical Industry     

Effect of drought on polyamine metabolism,yield, protein content and in vitro protein digestibility in tepary (Phaseolus acutifolius) and common (Phaseolus vulgaris) bean seeds

The objective of the present study was to investigate the effect of drought on the metabolism of proline, ornithine and polyamines, and the enzymes involved in their synthesis and degradation, in tepary and common bean seeds. Furthermore, the effect on seed yield, protein content and in vitro protein digestibility was also studied. Genotypes of tepary bean (Phaseolus acutifolius) used were: PI‐301‐801 from Nicaragua; G‐400‐35 from Oaxaca, Mexico; L‐242‐24 and L‐242‐36 from Sonora, Mexico; L‐172 from Arizona, USA; and the common bean (Phaseolus vulgaris) variety Flor de Mayo Bajío (FMB) from Mexico. The cultivars were grown in a greenhouse under controlled temperature, light and humidity. Water content in plants (WCP) decreased when irrigation was stopped (1 and 2 weeks after blooming). Common bean had the lowest WCP value (73.75%), while the best genotypes were PI‐301‐801 (91.62%), G‐400‐35 (88.70%) and L‐242‐24 (85.73%). Tepary bean plants had superior water absorption capacity, which helped to increase yield. De novo synthesis of drought proteins may explain the increased protein content present under drought conditions. The results suggest that water stress induced ornithine amino transferase activity and ornithine concentration. Proline also increased under drought conditions (p < 0.05). Genotypes L‐242‐24 and G‐400‐35, which had the highest yield, also had a major concentration of polyamines under water stress. The results also suggest that arginase activity participated in amino acid synthesis such as ornithine and, consequently, in the protein concentration under water stress. Genotypes G‐400‐35 and L‐242‐24 are good alternatives for cultivation in arid zones. Copyright © 2003 Society of Chemical Industry     

Influence of water and nitrogen deficit on fruit ripening and aroma potential of Vitis vinifera L cv Sauvignon blanc in field conditions

S‐Cysteine conjugate precursors of three volatile thiols were monitored in Vitis vinifera L cv Sauvignon blanc grapes during fruit ripening to assess the influence of vine water and nitrogen status on the grape aroma potential in field conditions. Four dry farmed plots were studied in the Pessac‐Léognan and Graves appellations (Bordeaux area) in 1998, which was a very dry vintage, and in 1999, when regular summer rainfall occurred. Soil water‐holding capacity ranged from very low to high. Soil total nitrogen content was related to soil organic matter content, which was highly variable on the four plots. Vine vigour was enhanced by both high water and nitrogen status. Major compounds in grapes depended mainly on vine water status. Water deficit‐stressed vines produced small berries with low sugar and low total acidity. Grape aroma potential was highest in vines under mild water deficit and moderate nitrogen supply. Severe water deficit stress seemed to limit aroma potential, as did nitrogen deficiency. Consequences for site selection and irrigation management for Sauvignon blanc are discussed. Copyright © 2004 Society of Chemical Industry     

Soil moisture stress‐induced alterations in bioconstituents determining tea quality

The impact of water stress on the biochemical constituents that determine black tea quality was investigated. Phenylalanine ammonia lyase (PAL) activity was highest in the drought tolerant ‘Assam’ cultivar UPASI‐2, followed by UPASI‐8 and UPASI‐9, under non‐stress conditions. Under soil moisture stress a reduction in PAL activity was found in all three clones investigated. A strong positive correlation was observed between an increase in soil moisture deficit and a decrease in PAL activity. Lower PAL activity correlated well with lower synthesis of flavanols such as epigallocatechin gallate (EGCG) and epicatechin gallate (ECG), which are important precursors of theaflavin‐3,3′‐digallate that determines final tea quality. Altered synthesis of EGCG and ECG could be due to their molecular rearrangement at elevated leaf temperature during drought. Synthesis of quality constituents such as gallic acid and caffeine declined significantly owing to both drought and waterlogging stress. The reduction in gallic acid due to water stress could lead to lower synthesis of theaflavin fractions such as epitheaflavic acid, epitheaflavic acid‐3′‐gallate and theaflavic acid and, thereby, quality deterioration. Similarly to drought, flooding stress was also found to alter the biochemical constituents necessary for tea quality. Copyright © 2003 Society of Chemical Industry     

硫酸盐法蒸煮过程中木素-聚木糖复合体化学结构的变化

以木素脱氢聚合物(DHP)和聚木糖为原料,合成了木素-聚木糖复合体(DHPXC);以该复合体作为植物原料中木素-碳水化合物复合体(LCC)模拟物,对其进行了硫酸盐法蒸煮。对蒸煮后产物进行了红外光谱和高分辨率液体核磁共振分析,探讨了硫酸盐法蒸煮过程中植物纤维原料中LCC的结构变化和降解情况。研究结果表明,木素-聚木糖复合体经硫酸盐法蒸煮后,酸不溶物中含有大量聚木糖,聚木糖与木素依然以LCC的形式连接在一起。蒸煮后木素结构中含有一定量的肉桂醇结构,木素结构单元之间主要通过β-β结构连接,还含有一定量的β-5和β-O-4结构。     

Water sorption kinetics of superabsorbent hydrogels of saponified cassava starch‐graft‐poly(acrylamide)

Superabsorbent polymers (SAPs) are hydrophilic polymeric networks that can absorb, swell and retain large quantity of water and other physiological fluids. In this paper, the water sorption pattern and kinetics of cassava starch based SAP hydrogels were studied under different conditions of swelling such as soaking duration, pH, presence of salts, and particle size of the hydrogel. The kinetics was studied using Voigt‐based viscoelastic model to determine the rate parameter and the swelling rate (SR). It was noted that under all conditions, the water sorption followed a second order kinetics. The absorbency was directly proportional to the rate of swelling. But when the sample was allowed to swell in aqueous solutions of CaCl₂ and AlCl₃, the absorbency as well as the SR was irregular. The particle size also had significant effect on water absorption by the SAP and the polymer with smaller particles showed more absorption than those with larger particle size. The solvent induced phase transition of the superabsorbent hydrogel was also studied.     

烯效唑浸种对大豆苗期抗旱性的影响

为明确烯效唑对大豆苗期抗旱性的影响,以浙春3号为试材,采用不同浓度（0、0．05、0．1、0．2和0．4mg／kg）烯效唑浸种,探讨不同水分胁迫（正常供水、轻度胁迫和中度胁迫）下烯效唑对大豆苗期的抗旱效应。结果表明：烯效唑浸种降低了苗高,提高了大豆出苗率、茎粗和根冠比;同时还提高了叶片相对含水量、脯氨酸（Pro）含量和可溶性糖含量。烯效唑处理降低了丙二醛（MDA）含量,从而降低了脂质过氧化程度,提高了保护性酶的活性。正常供水下,SOD、POD和CAT酶活性均以0．1mg／kg处理最高,分别较对照提高了18．75％、8．43％和37．4％;轻度水分胁迫下,SOD、POD和CAT酶活性均以0．2mg／kg处理最高,分别较对照提高了23．53％、11．63％和47．5％;中度水分胁迫下,SOD、POD和CAT的酶活性均以0．4mg／kg处理最高,较对照分别提高了22．86％、11．2％和56．1％。可见,适宜浓度的烯效唑浸种可改善套作大豆苗期生长,提高抗旱能力。     

Influence of rootstock on drought response in young 'Gale Gala' apple (Malus domestica Borkh.) trees

BACKGROUND: Drought is a major environmental stress limiting plant growth, productivity, and survival worldwide. Rootstocks are widely used to enhance plants resistance to drought stresses. This study determined influence of rootstock on drought responses in 1‐year‐old ‘Gale Gala’ apple trees grafted onto Malus sieversii or M. hupehensis. RESULTS: Choice of rootstock resulted in differential response to drought stress. Specifically, M. sieversii caused less drought‐induced reduction in relative growth rate, biomass accumulation, leaf area, leaf chlorophyll content, relative water content, photosynthesis rate and maximum chlorophyll fluorescence yield but greater increase in whole‐plant water use efficiency compared to M. hupehensis. Secondly, compared with M. hupehensis, M. sieversii caused less drought‐induced accumulation of reactive oxygen species but more increase in activities of antioxidant enzymes. In addition, xylem sap abscisic acid concentration was greater in trees grafted onto M. hupehensis than in those grafted onto M. sieversii under drought stress. CONCLUSION: ‘Gale Gala’ trees' response to drought stress was associated with the rootstock's genotype onto which it was grafted. Trees with M. sieversii as rootstock are more drought resistant than trees with M. hupehensis as rootstock, which suggests that M. sieversii can be widely used as rootstock in arid and semi‐arid regions. Copyright © 2012 Society of Chemical Industry     

Reduced irrigation and rootstock effects on vegetative growth,yield and its components,and leaf physiological responses of Shiraz

Background and Aims: The study investigated whether rootstocks can modify grapevine responses to reduced irrigation. Methods and Results: Drip-irrigated Shiraz vines on eight rootstocks were subjected to industry standard and 30% reduced irrigation regimes over four seasons. Reducing irrigation decreased pruning weights and yield, but did not consistently affect irrigation water use index (IWUI). It increased leaf Δ¹³C. Reduced irrigation and elevated vapour pressure deficit (VPD) were associated with decreases in leaf water potential (ψ_l), leaf stomatal conductance and assimilation rate. Reducing irrigation raised leaf transpiration efficiency, whereas elevated VPD lowered it. These effects of reduced irrigation were independent of rootstock. Vines grafted to 101-14 had a higher ψ_l and achieved the highest yield and IWUI. The yields of vines grafted to Ramsey, Schwarzmann and 140 Ruggeri were also high. Vines grafted to 101-14, Ramsey and 1103 Paulsen had the higher rates of leaf assimilation. Rootstock did not affect Δ¹³C. Conclusion: The gain in leaf transpiration efficiency caused by reducing irrigation was not associated with a gain in IWUI. Rootstocks 101-14, Ramsey, Schwarzmann and 140 Ruggeri achieved higher yields and IWUI under both standard and reduced irrigation regimes. Significance of the Study: Among grafted vines growing on saline soil but receiving non-saline irrigation water and subject to a 30% reduction in irrigation, the yield responses of vines grafted on rootstocks rated as having good drought tolerance were the same as those of vines grafted on rootstocks rated as having poor drought tolerance.     

Grapevine canopy response to a high‐temperature event during deficit irrigation

Background and Aims: Despite much anecdotal evidence, there has been little scientific investigation of the potential effects of a high‐temperature event on grapevines during deficit irrigation. This study examined the interaction between temperature and water status on leaf physiology. Methods and Results: Two experiments used Cabernet Sauvignon cuttings grown in a glasshouse at approximately 27–30°C before deficit irrigation treatments were imposed. When water stress was apparent, a 2‐day high‐temperature event with maximum daytime temperatures of approximately 40–45°C was generated. Leaf damage, stomatal conductance and water potential of deficit‐irrigated vines were all affected to a greater extent than in the well‐watered vines. Conclusions: The negative effects of a high‐temperature event on vine physiology were more severe in vines experiencing water stress than in well‐watered vines, but recovery was rapid even without re‐watering. Significance of the Study: An increase in the use of deficit irrigation will lead to a greater likelihood of vines being water stressed on hot days, and the observed responses indicate that this will result in greater damage to the vine.     

Selenium (Se) improves drought tolerance in crop plants – a myth or fact?

Climate change has emerged as one of the most complex challenges of the 21st century and has become an area of interest in the past few decades. Many countries of the world have become extremely vulnerable to the impacts of climate change. The scarcity of water is a serious concern for food security of these countries and climate change has aggravated the risks of extreme events like drought. Oxidative stress, caused by a variety of active oxygen species formed under drought stress, damages many cellular constituents, such as carbohydrates, lipids, nucleic acids and proteins, which ultimately reduces plant growth, respiration and photosynthesis. Se has become an element of interest to many biologists owing to its physiological and toxicological importance. It plays a beneficial role in plants by enhancing growth, reducing damage caused by oxidative stress, enhancing chlorophyll content under light stress, stimulating senesce to produce antioxidants and improving plant tolerance to drought stress by regulating water status. Researchers have adopted different strategies to evaluate the role of selenium in plants under drought stress. Some of the relevant work available regarding the role of Se in alleviating adverse effect of drought stress is discussed in this paper. © 2015 Society of Chemical Industry     

The effect of changing patterns in soil-moisture availability on grapevine root distribution, and viticultural implications for converting full-cover irrigation into a point-source irrigation system

Improvements in the efficiency of water use in Australian vineyards have included a move away from diffuse or 'total cover' irrigation techniques to drip irrigation systems. This change in irrigation method has a significant effect on moisture distribution within the soil profile, with implications for root growth, root-system architecture, and soil-water acquisition. Those issues are addressed in this paper. Our report is based on grapevines that had been established under a diffuse irrigation system (overhead sprinklers or microjets) and subsequently converted to drippers. Results are also presented to show the influence of soils with different water holding capacities on root distribution within a single vineyard. Variations in soil texture within a vineyard were found to influence the vertical distribution of roots, whereas irrigation history had more influence on horizontal variations in root density within a depth range. Conversion of vines from sprinkler irrigation to drippers resulted in a marked increase in total root mass (volume) under the drip line, particularly 25–50 cm below the surface. Roots were differentially influenced by irrigation history according to their diameter class. Under drip irrigation, the largest increase in root-length density occurred with roots in diameter classes between 1 and 4 mm diameter. Grapevines established under sprinklers, and subsequently converted to drip irrigation, had significantly larger root systems (within the volume of soil sampled) than did vines maintained under sprinklers throughout. Therefore, vines established under sprinkler irrigation and then converted to drippers may be better equipped to cope with deficit irrigation during drought (via either RDI or PRD), by virtue of those additional roots.     

Effect of reduced irrigation on growth,yield, ripening rates and water relations of Chardonnay vines grafted to five rootstocks

Background and Aims: In the first decade of the 21st century, drought within the Murray–Darling Basin has reduced the amount of water available for irrigation. We investigated whether the response of vines to reduced irrigation was modified by rootstock. Methods and Results: Reduced irrigation (5 versus 8 ML/(ha·year)) was applied to Chardonnay vines grafted to five rootstocks (Ramsey, 140 Ruggeri, 1103 Paulsen, 110 Richter and K51‐40) for four seasons. It decreased the yield from 29.3 to 26.7 kg/vine, and increased the irrigation water use index (IWUI) from 4.7 to 6.6 t/(ha·ML), but gains in this index declined as the trial progressed. The values of mid‐afternoon leaf water potential were not affected by reduced irrigation, but leaf CO₂ assimilation declined from 13.1 to 11.7 µmol/(m²·s). These effects were independent of rootstock. Reduced irrigation did not increase soil salinity (ECe) or vine tissue Na and Cl concentrations. Vines on Ramsey and 1103 Paulsen rootstocks had higher yields, 32.2 and 30.0 kg/vine, respectively, and the highest IWUIs, 5.9 and 5.5 t/(ha·ML). In two of the three seasons, reducing irrigation did not affect the rates of ripening (°Brix/growing degree days) excepting vines on 1103 Paulsen. Ripening rates varied by 1.5‐fold between seasons. Conclusion: The yield and growth responses of Chardonnay vines to a 35% reduction in irrigation were not modified by rootstock. Significance of the Study: Reducing irrigation did not lead to a build‐up of soil salts. The response of vines to reduced irrigation on rootstocks rated as having good drought tolerance was the same as that for vines on a rootstock rated as having poor drought tolerance.     

Short communication: Effect of corn planting population on phosphorus concentration and uptake in corn silage

Greater utilization of nutrients reduces the potential runoff of nutrients to bodies of water. The objective of this study was to determine the concentration of P in corn biomass to estimate the removal of P from the soil when planting corn at different population levels. Whole-plant corn samples were collected during an on-farm research project conducted previously. The study included 7 different growing and harvesting conditions. In each cornfield, corn was planted in plots at a theoretical seeding rate of 55,000, 70,000, 85,000, and 100,000 seeds/ha. Each seeding rate had 4 replicates within each field. At harvesting time, 5 consecutive plants from the 2 center rows and at 2 randomly selected spots within each plot were cut by hand at 15 cm above ground. Whole plants were weighed and chopped. After mixing thoroughly, a sample of the chopped material was placed in a bag, immediately placed in a cooler with dry ice, and transferred to the laboratory for storage. After thawing and drying, samples were ground and analyzed for P concentration. Single plant biomass and the number of standing plants at harvesting were used to determine dry matter yield. Total extraction of P was estimated as the product between plant biomass and P concentration. All variables were analyzed using a statistical model that included the effects of field, planting population, planting population nested within field, and random residual error. The concentration of P in the corn plant was greatest for 55,000 and 70,000 plants/ha (0.250% dry matter) and least for 85,000 and 100,000 plants/ha (0.235% dry matter), whereas the uptake of P through the harvested biomass increased when corn planting population increased. In conclusion, increasing the planting population of corn for silage can increase P uptake from the soil, therefore reducing the potential runoff of P to bodies of water.     

Developmental variation in sensitivity of Vitis vinifera L. (Shiraz) berries to soil water deficit

A large-scale, long-term irrigation experiment was established near Waikerie in the South Australian Riverland to investigate the feasibility of controlling berry size and ripening at the vineyard scale with modern irrigation systems. Irrigation treatments were devised to impose water stress, by withholding irrigation, during four periods of berry development after flowering of Vitis vinifera (variety Shiraz). Varying water deficits were achieved during each period and between the four seasons, which were climatically diverse. In one season water deficit during the period after flowering resulted in the greatest reduction in berry weight compared with that of well-watered vines, however, in another, water deficit during this period had no effect on berry weight. By comparison, berries appeared to be insensitive to water deficit during the month before harvest in all four seasons. A soil water deficit index was derived to compare the varying levels of water deficit between treatments and seasons on berry development. Deficit effects on berry development were assessed using either comparative growth rate or berry weight near harvest. Regression analysis of berry development against soil water deficit indicated that berries were most sensitive to water stress during the post flowering period.     

Water‐saving approaches for improving wheat production

The greatest fear of global climate change is drought. World‐wide, 61% of countries receive rainfall of less than 500 mm annually; domestication of wheat first occurred in such a semiarid region of southwestern Asia, and it seems that wheat foods originally came from dryland gardens. Wheat plants respond to drought through morphological, physiological and metabolic modifications in all plant parts. At the cellular level, plant responses to water deficit may result from cell damage, whereas other responses may correspond to adaptive processes. Although a large number of drought‐induced genes have been identified in a wide range of wheat varieties, a molecular basis for wheat plant tolerance to water stress remains far from being completely understood. The rapid translocation of abscissic acid (ABA) in shoots via xylem flux, and the increase of ABA concentration in wheat plant parts correlate with the major physiological changes that occur during plant response to drought. It is widely accepted that ABA mediates general adaptive responses to drought. For a relatively determinate target stress environment, and with stable genotype × environment interaction, the probability for achieving progress is high. This approach will be possible only after we learn more about the physiology and genetics of wheat plant responses to water stress and their interactions. The difficulties encountered by molecular biologists in attempting to improve crop drought tolerance are due to our ignorance in agronomy and crop physiology and not to lack of knowledge or technical expertise in molecular biology. Copyright © 2005 Society of Chemical Industry     

干旱胁迫后复水对烤烟生长及其生理特性的影响

  目的  为明确干旱胁迫后复水对烤烟生长及其生理基础的影响。  方法  采用盆栽试验方法,以耐旱型烤烟品种“豫烟6号”和水分敏感型“豫烟10号”为试验材料,设置正常供水、轻度干旱、中度干旱、轻度干旱后复水和中度干旱后复水5个处理,比较分析干旱胁迫后复水对烤烟生长及其生理特性的影响。  结果  （1）随着干旱的加剧,两个烤烟品种生长受到抑制,生理性能下降,株高、茎围、最大叶长、最大叶宽、最大叶面积、有效叶片数、根系干重和单株干重均降低或显著降低,叶绿素含量、净光合速率（P_n）、气孔导度（G_s）、蒸腾速率（T_r）、PSII最大光能转化效率（F_v/F_m）、PSⅡ实际光化学效率（Φ_PSⅡ）和光化学淬灭系数（qP）均显著降低,而非光化学猝灭系数（NPQ）、胞间二氧化碳浓度（C_i）、丙二醛（MDA）含量、超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性均显著增加;与正常供水相比,豫烟10号在干旱胁迫下各指标变化幅度大于豫烟6号,对干旱较敏感。（2）干旱胁迫后复水,与干旱处理结束时相比,两个烤烟品种生长得到明显恢复,光合作用增强,抗氧化系统平衡得到明显改善。豫烟10号在干旱胁迫后复水各指标变化幅度均大于豫烟6号,干旱胁迫后复水恢复较好。  结论  在干旱胁迫下,两个烤烟品种的生长和生理性能均受到不同程度的抑制,且均与正常供水处理间差异显著;复水后,两个烤烟品种的生长及其生理性能均得到不同程度的恢复,其多数指标均以中度干旱胁迫后复水处理恢复较好,且与正常供水处理无显著差异。      

Allometric and biochemical responses of grapevines subjected to drought and enhanced ultraviolet‐B radiation

Background and Aims: The aim of this study was to evaluate differences in adaptive responses in grapevines (Vitis vinifera L. cv Soultanina) exposed to either drought, enhanced ultraviolet‐B (UV‐B) radiation or the combination of the two environmental stresses. Methods and Results: Results indicated pronounced effects on allometric parameters in plants exposed to the enhanced UV‐B radiation. The combined application of drought and enhanced UV‐B radiation considerably affected shoot growth rate and leaf dry weight. Guaiacol peroxidase (GPX, EC 1.11.1.7), ascorbate peroxidase (APX, EC 1.11.1.11), superoxide dismutase (SOD, 1.15.1.1) and catalase (CAT, 1.11.1.6) activities increased significantly in the enhanced UV‐B radiation treatment. Drought resulted in a significant increase in proline concentration, while the exposure of plants to enhanced UV‐B radiation resulted in the production of UV‐B absorbing compounds (UV_abs). Conclusions: Under drought conditions proline accumulation seemed to be the main mechanism of adaptation contributing to plant's antioxidant defence. On the other hand, under enhanced UV‐B radiation, the accumulation of the UV‐B absorbing compounds and the increase in antioxidant enzymes activities constitute the main mechanisms of grapevine adaptation. Significance of the Study: The data obtained indicate the occurrence of two different mechanisms of adaptation in response to the stressor applied. Furthermore, the patterns of proline and UV_abs concentration changes under stress conditions suggest that the biosynthesis of these two compounds might follow competing metabolic pathways.