Cadmium induced oxidative stress and changes in soluble and ionically bound cell wall peroxidase activities in roots of seedling and 3–4 leaf stage plants of <Emphasis Type="Italic">Brassica juncea</Emphasis> (L.) czern

Metabolic adaptations to heavy metal toxicity in plants are thought to be related with developmental growth stage and the type of metal by which plant is affected. In the present study, changes in ionically bound CWP, soluble peroxidase activity, H(2)O(2) level and Malonaldehyde content in roots of cadmium and copper stressed seedlings and cadmium stressed 3-4 leaf stage plants of Brassica juncea were investigated. Cadmium inhibits root growth and reduces fresh biomass. The reduction in root growth and fresh biomass is correlated with increased lipid peroxidation and reduced tolerance. Treatment with cadmium resulted in an increase in ionically bound CWP activity in roots of seedlings but no significant change in its activity was found in roots of 3-4 leaf stage plants. Increased level of H(2)O(2) in roots of cadmium and copper treated seedlings, show a direct correlation with increased activity of ionically bound CWP. H(2)O(2) level in 3-4 leaf stage plant roots was found to be very low. Soluble peroxidase activity decreased in cadmium (50 and 100 mu-icroM) treated seedlings but it was ineffective to cause any change in its activity in 3-4 leaf stage plants. Copper treated seedlings showed an increase in ionically bound CWP activity, H(2)O(2) level and MDA content. Ascorbic acid (50 mM) pretreated seedlings shows significant decrease in ionically bound CWP activity when exposed to 50 muM cadmium. Hence, it is concluded that inhibition of root growth in Brassica juncea seedlings by cadmium, is associated with CWP catalyzed H(2)O(2) dependent reactions which are involved in metabolic adaptations to heavy-metal stress.     

东乡野生稻回交重组系的抗旱性评价体系

选用协青早B//东乡野生稻/协青早B回交重组系及其亲本共79份水稻材料,研究了水稻发芽期、苗期、孕穗期、成熟期的种子萌发抗旱指数等31个指标与东乡野生稻回交重组系抗旱性的关系.结果表明:15％ PEG-6000溶液处理的相对发芽势、20％ PEG-6000溶液处理的种子萌发抗旱指数和相对发芽势及水分胁迫后最长根长、苗高、根鲜质量、根干质量、根系相对含水量、萎蔫率、叶片可溶性糖含量、叶片脯氨酸含量、叶片丙二醛含量、叶片相对含水量、卷叶级别、株高、单株分蘖数、单株有效穗数、穗实粒数、着粒密度、结实率、千粒重等21个指标的相对值与抗旱系数或抗旱指数的相关性显著.通过逐步回归分析筛选出9个抗旱性鉴定指标:20％ PEG-6000溶液处理的相对发芽势及水分胁迫后根干质量、根系相对含水量、叶片可溶性糖含量、叶片脯氨酸含量、叶片丙二醛含量、单株有效穗、结实率和千粒重的相对值.根据这些指标和偏相关系数,建立了不同时期的抗旱性评价(D值)方程和评价体系,可对东乡野生稻回交重组系抗旱性进行较好的评价.     

干旱胁迫对持绿性高粱叶片渗透调节及叶绿体超微结构的影响

在盆栽条件下,研究了开花期和灌浆期干旱胁迫(土壤含水量为田间最大持水量的45%~50%)对持绿性高粱(B35)和非持绿性高粱(三尺三)叶片水分、渗透调节物质以及叶绿体超微结构的影响.结果表明: 干旱胁迫下,两高粱品系叶片自由水含量下降,束缚水含量增加,相对含水量降低,水分饱和亏缺增加,相对电导率增大,但三尺三各指标的变化幅度均大于B35.对于渗透调节物质,干旱胁迫下,三尺三可溶性糖含量的增幅大于B35,脯氨酸含量的增幅小于B35,可溶性蛋白含量的降幅大于B35.干旱胁迫下,B35与三尺三的叶绿体超微结构均受到一定程度的破坏,但B35叶绿体结构保持相对完好,受损程度明显小于三尺三.在干旱胁迫下,持绿性高粱通过较强的渗透调节表现出更好的干旱适应能力.
     

Application of photochemical parameters and several indices based on phenotypical traits to assess intraspecific variation of oat (<Emphasis Type="Italic">Avena sativa</Emphasis> L.) tolerance to drought

Functionality of the photosynthetic system under water stress is of major importance in drought tolerance. Oat (Avena sativa L.) doubled haploid (DH) lines obtained by pollination of F ₁ oat crosses with maize were used to assess the differences in plant genotypic response to soil drought. The investigations were based on the measurements of gas exchange and chlorophyll a fluorescence kinetics. Drought was applied to 17-day-old seedlings by withholding water for 14 days and subsequent plant recovery. Non-stressed optimally watered plants served as controls. Yield components were determined when plants reached full maturity. It was shown differences among the oat lines with respect to drought stress susceptibility (SI) and stress tolerance index mean productivity and drought susceptibility index. Sensitivity to drought of individual DH lines was significantly different, as demonstrated by the correlation between drought susceptibility index and yield components, such as dry weight (GW) or grain number (GN) of the harvested plants. GW and GN were lower in drought-sensitive genotypes exposed to drought stress compared to those resistant to drought. The principal component analysis allow to separate three groups of lines differing in their sensitivity to drought stress and indicated that tolerance to drought in oat has a common genetic background.     

Physiological and biochemical parameters for identification of QTLs controlling the winter triticale drought tolerance at the seedling stage

The genetic map of the triticale is created on the basis of double-haploid (DH) lines, derived from F1 hybrids of a cross between the parental line Saka3006 and Modus. In order to localise drought resistance genes, it is necessary to find a phenotype feature which clearly differentiates between parental lines under drought stress conditions. With the future in mind, the aim of the presented studies was to analyse differences in the response to drought stress, between Saka3006 and Modus. Analyses of the water status of leaves, and the activity of the photosynthetic apparatus and protective mechanisms relating to the accumulation of phenolic compounds, were carried out. The studies were completed during the tillering phase.Statistically significant changes, between genotypes experiencing the drought period, were noticed for the osmotic potential, leaf water content, some parameters of chlorophyll fluorescence, and for phenolics and the ferulic acid content. On the basis of the studies, the Saka genotype can be considered drought resistant due to higher leaf water content caused, probably, by smaller hydraulic resistance relative to Modus. The activity of its photosynthetic apparatus during drought was higher than that for the Modus genotype. The high level of phenolic compounds, which can act as photoprotectors and free radical scavengers, was also maintained. All the mentioned parameters can represent the potential phenotype features, which allow the identification of resistance genes on the genetic map of the triticale, which is currently being created.     

Contribution of arbuscular mycorrhizal fungi (AMF) to the adaptations exhibited by the deciduous shrub Anthyllis cytisoides L. under water deficit

Anthyllis cytisoides L. is highly colonized by arbuscular mycorrhizal fungi (AMF) and behaves as a drought-avoider species in the field. Our objectives were: (1) to study the response of A. cytisoides when exposed to moderate (acclimation) or severe (peak) drought and subsequent rewatering under nursery conditions; and (2) to verify if AMF improved the adaptation of A. cytisoides to stress. The soil compactness in drought-acclimated treatments increased four times compared with that of well-watered controls, which could reinforce the effects of water deficit on plant physiology. Photosynthetic rates decreased by around 50% and 70% and leaf conductance decreased by 40% and 50% in drought-acclimated non-mycorrhizal and mycorrhizal plants, respectively. Peak drought limited plant growth, accelerated leaf senescence and induced the conversion of starch into soluble sugars in the leaves of stressed plants. The accumulation of sugars could contribute to a decrease in water potential in order to achieve the required tension to let water move from soil to shoot. Mycorrhizal plants showed a two-fold higher chlorotic leaf biomass than non-mycorrhizal plants under severe drought. Moreover, mycorrhizal A. cytisoides showed enhanced epicuticular waxes on the surfaces of the remaining green leaves. Increased leaf senescence, together with wax deposition, could reduce whole plant transpiration, thus allowing mycorrhizal plants to maintain a higher leaf relative water content (50%) than non-mycorrhizal plants (35%). After drought recovery, leaf abscission in stressed mycorrhizal plants was 10 times greater than that in non-mycorrhizal plants. The results suggest that AMF conferred greater responsiveness of A. cytisoides to drought. Enhanced wax deposition and leaf senescence could be an ecological adaptation to cope with severe water deficit.     

不同水分条件下小麦灌浆期功能叶片的遗传特性

2005-2007年,以小麦DH群体（旱选10号×鲁麦14）的150个株系及其亲本为材料,研究在灌溉和雨养两种水分条件下,小麦灌浆中期上部3片功能叶的长、宽及基角遗传基础及其与产量性状的关系.结果表明：与灌溉条件下的性状相比,雨养条件下小麦灌浆中期上部3片功能叶的长和宽均显著降低,而叶基角表现复杂.两种水分条件下,DH群体所有性状均表现超亲分离,变异系数在5.1%～45.9%,性状平均值多数介于双亲之间;旗叶基角遗传力均最高(91%和97%),而倒3叶基角均最低 (23%和31%);控制旗叶基角的基因数目均最少,灌溉和雨养条件下均分别为4对和2对,控制倒3叶基角的基因数目2007年均最多,分别为21和25对;两种水分条件下控制上部3叶基角,以及灌溉条件下控制倒3叶长的多基因间存在互补作用.3片功能叶长、宽与穗粒数、穗粒重之间多数为显著正相关, 倒3叶长、旗叶基角、倒2叶基角与千粒重、单株产量呈显著正相关,但相关系数均较小（<0.481）.因此,可以在育种早代对上部3叶长、宽进行比较严格的选择,而对叶基角的选择应在育种高代进行;在小麦上部3片功能叶生长的关键时期保证适宜的土壤水分,能够促进叶片正常生长,提高产量.     

QTLs linked to leaf epicuticular wax,physio-morphological and plant production traits under drought stress in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Drought stress is the major constraint to rice (Oryza sativa L.) production and yield stability in rainfed ecosystems. Identifying genomic regions contributing to drought resistance will help to develop rice cultivars suitable for rainfed regions through marker-assisted breeding. Quantitative trait loci (QTLs) linked to leaf epicuticular wax, physio-morphological and plant production traits under water stress and irrigated conditions were mapped in a doubled haploid (DH) line population from the cross CT9993-5-10-1-M/IR62266-42-6-2. The DH lines were subjected to water stress during anthesis. The DH lines showed significant variation for epicuticular wax (EW), physio-morphological and plant production traits under stress and irrigated conditions. A total of 19 QTLs were identified for the various traits under drought stress and irrigated conditions in the field, which individually explained 9.6%–65.6% of the phenotypic variation. A region EM15_10-ME8_4-R1394A-G2132 on chromosome 8 was identified for leaf EW and rate of water loss i.e., time taken to reach 70% RWC from excised leaves in rice lines subjected to drought stress. A large effect QTL (65.6%) was detected on chromosome 2 for harvest index under stress. QTLs identified for EW, rate of water loss from excised leaves and harvest index under stress in this study co-located with QTLs linked to shoot and root-related drought resistance traits in these rice lines and might be useful for rainfed rice improvement.     

Variation in Drought Tolerance of Different Stylosanthes Accessions

Twenty genotypes of Stylosanthes consisting four species were evaluated under rain fed condition employing biochemical and physiological attributes to select drought tolerant lines. Relative water content measured at 50 % flowering stage of the plants showed significant variations among the lines which ranged from 32.11 in S. scabra RRR94-86 to 83.33 % in S. seabrana 2539. The results indicated that S. scabra genotypes were more tolerant to drought over other lines as evidenced by high leaf thickness, proline accumulation, content of sugars and chlorophyll, and nitrate reductase activity.     

Short-term drought response of two white clover clones, sensitive and tolerant to O3

In order to study observed differences in water status between Trifolium repens L. cv. Regal NC-R and NC-S biotypes, tolerant and sensitive to ozone, respectively, and trying to identify possible environmental strains for this widely used ozone biomonitoring system, the response of these two biotypes to a short-term drought was evaluated. The evolution of both soil and plant water status along with leaf gas exchange parameters, leaf ascorbate peroxidase (EC 1.11.1.11), glutathione reductase (EC 1.8.1.7), superoxide dismutase (EC 1.15.1.11) enzymatic activities and leaf content in total soluble protein, total soluble sugars, proline for an equal number of clones of each biotype under drought and control treatments was registered for 5 days under greenhouse conditions and summer direct sunlight. The results obtained show that the water requirement of sensitive NC-S clones is higher, as these tend to display higher values of leaf conductance and water use under optimal water availability. What is more, when the short-term drought is imposed, symptoms of oxidative stress and a negative impact on most of the measured parameters are displayed at an earlier stage in this biotype, proving it to be more sensitive to low water availability. It is therefore suggested that these differences might be linked with the existing variability in ozone sensitivity between the biotypes and that at the same time, they could result in a poorer performance of this biomonitoring system in field assays under conditions of high evapotranspiratory demand, such as those registered during summer time in Southern Europe.     

Physiological changes in them in post-stress emerging <Emphasis Type="Italic">Ctenanthe setosa</Emphasis> plants under drought conditions

The capability of Ctenanthe setosa (Rosc.) Eichler (Marantaceae), pre-exposed to severe drought stress, of adaptation to a new drought conditions was investigated. C. setosa unstressed plants were exposed to drought period of 70 days. These plants were named as primary-stress plants (PS). They were trimmed, and new plants were produced from their rhizomes. New growing plants were named as post-stress emerging (PSE) plants. It was observed that leaf area and petiole length of PSE plants were reduced, as compared to unstressed plants. When PSE plants were exposed to a second drought-stress cycle, it was determined that the degree of their leaf rolling was higher but their relative water content (RWC) was less than these parameters of PS plants during drought period. However, at the 81% rolling degree, RWC in PSE plants was higher than in PS plants. Consequently, it can be said that the PSE plant were more resistant to a new drought stress than unstressed and PS plants. In the leaves of PSE plants, which were exposed to a second drought-stress period, the content of soluble protein decreased in the early period of drought, but increased in the later periods. Also, the content of reducing sugar in PSE plants gradually decreased during the stress period. Proline content increased markedly during drought period, whereas peroxidase activity increased up to the 60th day and then decreased. This text was submitted by the authors in English.     

开花期土壤短期干旱和复水对大豆光合作用和产量的影响

以大豆(Glycine max)为材料, 研究开花期土壤水分变动对叶片光合生理以及产量形成的影响, 以期为大豆的节水栽培和水分高效利用提供理论依据。研究发现, 大豆叶片气孔导度(Gs)对土壤水分的匮缺更加敏感。干旱胁迫降低了叶片的净光合速率(Pn), 但复水后, 叶片水势和净光合速率等在实验过程中都可以得到迅速恢复, 并且蒸腾速率(Tr)、气孔导度和胞间CO₂浓度(Ci)在复水后的第3 天与对照相比显著提高, 表现出一定的超补偿效应。研究发现, 在开花期即使短期的土壤干旱, 也会对大豆后期的生物量及其分配产生较大的影响, 开花期干旱和复水, 显著降低了大豆叶片和茎的生物量, 使根茎比提高16.7% (P<0.05), 收获指数增加26.3%(P<0.05)。     

Genetic variation in physiological responses of mungbeans (<Emphasis Type="Italic">Vigna radiata</Emphasis> (L.) Wilczek) to drought

Mungbean is a relatively drought tolerant leguminous crop with a short life cycle. Using leaf water loss (LWL) as a screen for drought tolerance, two mungbean genotypes exhibiting more than two–fold variation in leaf water loss were explored for the genetic variation in their physiological and molecular responses to drought. Efficient stomatal regulation together with better photosynthetic capacity constituted an important trait combination for drought adaptation in water saving low LWL genotype. The stomatal closure under drought was accompanied with a concomitant down-regulation of farnesyl transferase gene. However, cooler canopy temperature, a well branched root system coupled with a relatively higher proline accumulation in water spending high LWL genotype constituted another set of adaptive traits operating when exposed to deficit soil moisture conditions. We report drought induced down-regulation of proline dehydrogenase and the presence of 118 base pair intron in this gene. The high seed yield of low LWL genotype despite a hotter canopy might be attributed to higher net assimilation and quantum yield recorded under drought in this genotype. Thus, these interlinked features contribute to adaptive mechanisms of mungbeans which is widely grown in harsh environments exposed to drought and high temperatures.     

Drought resistance of bermudagrass (Cynodon spp.) ecotypes collected from different climatic zones

The objectives of this paper were to (1) evaluate drought resistance of a large number of bermudagrass ecotypes collected from different climatic zones of regional Australia and compare their performance to commercial cultivars, (2) describe the mechanisms of drought resistance observed, and (3) investigate the relationship between geographic origins of the ecotypes and their drought resistance. Fifty-two genotypes of bermudagrass were evaluated in two field experiments using lysimeters 40 cm deep. The grasses were grown in well-watered conditions and then a drought treatment was imposed by withholding water and excluding rainfall using a portable rain-out shelter. Two criteria were used to select for drought resistance, i.e. survival period (SP), defined as the number of days after water was withheld to the stage when 100% leaf firing had occurred and Days₅₀ defined as the days required to reach 50% green cover. These experiments suggested that genotypes with superior drought resistance had lower stomatal conductance in the earlier phases of the dry-down period as suggested by less water use and higher canopy temperature depression. Lower water use during the early stage of dry-down resulted in more soil available water at the end of the drought period to extend green-leaf cover. There was no correlation between root dry matter and survival period/Days₅₀. We also found some ecotypes performed better in drought conditions than popular commercial cultivars. There was no relationship between drought resistance and geographic origins, suggesting that drought resistant ecotypes could be obtained from any climatic zone sampled in this study.     

Proline accumulation and nitrate reductase activity in contrasting sorghum lines during mid-season drought stress

Six lines of sorghum ( Sorghum bicolor L. Moench) with differing drought resistance (IS 22380, ICSV 213, IS 13441 and SPH 263, resistant and IS 12739 and IS 12744, susceptible) were grown under field conditions in the semi-arid tropics and analysed for proline and nitrate reductase activity (NRA; EC 1.6.6.1) during a mid-season drought. The resistant lines accumulated high levels of proline, while the susceptible lines showed no significant proline accumulation. Most of the proline was accumulated after growth of the plants had ceased. In a separate greenhouse experiment, most of the proline was found in the green rather than the fired portions of leaves. The levels returned to that of irrigated controls within 5 days of rewatering. Proline levels increased as leaf water potential and relative water content fell, and there was no apparent difference among the different sorghum lines with change in plant water status. Susceptible lines accumulated less proline than resistant lines as leaf death occurred at higher water potentials. Proline accumulation may, however, contribute to the immediate recovery of plants from drought. Leaf NRA reached high levels at about 35 days after sowing in both the stressed and irrigated plants, after which it declined. The decline in NRA was more pronounced in the stressed than in the irrigated plants and closely followed changes in the growth rate. Upon rewatering, NRA increased several-fold in all the lines and, in contrast to proline accumulation, genotypic differences in NRA were small, both during stress and upon rewatering. The high sensitivity of NRA to mild drought stress was reflected in the rapid decline of activity with small changes in leaf water potential and relative water content. The results are discussed in the light of a possible role for proline during recovery from drought, and the maintenance of NRA during stress and its recovery upon rewatering.     

立地条件和树龄对刺槐和小叶杨叶水力性状及抗旱性的影响

以形成黄土高原“小老树”的2种典型树种刺槐和小叶杨为对象,研究了立地条件(沟谷台地和沟间坡地)和树龄对两种树木叶水力学性质和抗旱性的影响,探讨“小老树”形成的水力生理机制.结果表明: 水分较好的沟谷台地上生长的两种树木的叶最大水力导度(K_max)明显大于水分较差的沟间坡地,叶水力脆弱性(P₅₀)也较高;随树龄增加,两种树木的K_max明显下降,但P₅₀差异不大.台地上生长的两种树木的叶表皮导度和PV曲线参数(膨压损失点时的相对含水量RWC_tlp、膨压损失点时的水势ψ_tlp、饱和含水量时的渗透势ψ_sat)均大于坡地;随树龄增加,两种树木的叶表皮导度显著下降,PV曲线参数出现不同程度的下降.两种树木K_max与ψ_tlp呈显著正相关,P₅₀与PV曲线参数之间存在一定的相关性,表明K_max与抗旱性之间存在一种权衡关系,P₅₀是反映两种树木的抗旱性特征之一.     

栽培稻旱胁迫叶片相关性状的遗传解析

利用籼稻窄叶青8号(ZYQ8)和粳稻京系17(JX17)衍生的加倍单倍体(DH)群体127个株系,2002年在杭州采用田间断水法栽培,在水分胁迫下,对叶片的卷叶、相对含水量和电导率3个性状进行了评价和QTL分析。结果表明,3个性状在DH群体中均存在双向超亲分离,接近正态分布,受数量性状基因的控制;检测到影响这些性状的6个QTL,其中卷叶3个(qLR—1,qLR—5和qLR—11)、相对含水量2个(qRWC—1和qRWC—6和电导率1个(qERC—6）。旱胁迫时,目测卷叶方便易行,适于对大批品种或资源筛选,对抗旱栽培稻品种的筛选和利用具有一定的指导意义。     

Evaluation of physiological screening tests for breeding drought resistant triticale (x <Emphasis Type="Italic">Triticosecale</Emphasis> wittmack)

Effects of soil drought on crop yield of 4 strains and 7 cultivars of spring triticale was investigated under field condition. The Drought Susceptibility Index (DSI) was evaluated in a two year experiment by the determination of grain loss in conditions of two soil moisture levels (drought-D and irrigated-IR). In the experiment response to drought was evaluated by different screening tests (leaf gaseous exchange, leaf water potential, chlorophyll content and fluorescence, leaf injury by drought and by simulated drought and heat temperature and water loss by excited leaf. The DSI values and the results of screening tests showed the genetic variation in the degree of drought tolerance. The values of DSI enabled the ranking of the tested triticale genotypes with respect to their drought tolerance and allow to divide them into three groups of drought susceptibility. Large differences among studied forms were observed also in changes of leaf water potential, fluorescence and leaf injury. For plants in vegetative stage of growth the tested breeding forms were easily separated into groups of different drought tolerance. Changes of ψ, Fv/Fm and LI as a screening tests were the most suitable techniques for estimation of degree of drought tolerance for triticale. Laboratory screening tests (leaf injury by simulated drought (LI_DS) and high temperature (LI_HT) and water loss (WL) of excited leaf conducted for nonstressed plants in most cases were significantly correlated with DSI. The statistically significant correlation between leaf water potential (ψ) was observed only with leaf fluorescence (Fv/Fm). Changes of Fv/Fm were significantly correlated with ψ, LI and LI_HT for 50 °C. Index of leaf injury (LI) by soil drought were significantly correlated with Fv/Fm, LI_DS (−1.0, −1.5 MPa), LI_HT (45 and 50°C) and water loss (WL). The correlation coefficient between the tests LI_DS and LI_HT were most of the considered cases statistically significant which indicate that the mechanism of membranes injury resulted from simulated drought or high temperature were similar in triticale. Water loss (WL) of excited leaves was the most suitable test for screening drought tolerance in triticale population. Changes of gaseous exchange parameters were not useful as screening test in this research.     

立地条件和树龄对刺槐和小叶杨叶水力性状及抗旱性的影响

以形成黄土高原“小老树”的2种典型树种刺槐和小叶杨为对象,研究了立地条件(沟谷台地和沟间坡地)和树龄对两种树木叶水力学性质和抗旱性的影响,探讨“小老树”形成的水力生理机制.结果表明:水分较好的沟谷台地上生长的两种树木的叶最大水力导度(Kmax)明显大于水分较差的沟间坡地,叶水力脆弱性(P50)也较高;随树龄增加,两种树木的Kmax明显下降,但P50差异不大.台地上生长的两种树木的叶表皮导度和PV曲线参数(膨压损失点时的相对含水量RWCtlp、膨压损失点时的水势ψtlp饱和含水量时的渗透势ψsat)均大于 坡地;随树龄增加,两种树木的叶表皮导度显著下降,PV曲线参数出现不同程度的下降.两种树木Kmax与ψtlp呈显著正相关,P50与PV曲线参数之间存在一定的相关性,表明Kmax与抗旱性之间存在一种权衡关系,P50是反映两种树木的抗旱性特征之一.