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1.
Despite exhaustive literature describing drought stress effects on photosynthesis in Gossypium hirsutum, the sensitivity of photosynthetic electron flow to water deficit is heavily debated. To address this, G. hirsutum plants were grown at a field site near Camilla, GA under contrasting irrigation regimes, and pre‐dawn water potential (ΨPD), stomatal conductance (gs), net photosynthesis (PN), actual quantum yield of photosystem II (ΦPSII) and electron transport rate (ETR) were measured at multiple times during the 2012 growing season. ΨPD values ranged from ?0.3 to ?1.1 MPa. Stomatal conductance exhibited a strong (r2 = 0.697), sigmoidal response to ΨPD, where gs was ≤0.1 mol m?2 s?1 at ΨPD values ≤ ?0.86 MPa. Neither ΦPSII (r2 = 0.015) nor ETR (r2 = 0.010) was affected by ΨPD, despite exceptionally low ΨPD values (?1.1 MPa) causing a 71.7 % decline in PN relative to values predicted for well‐watered G. hirsutum leaves at ΨPD = ?0.3 MPa. Further, PN was strongly influenced by gs, whereas ETR and ΦPSII were not. We conclude that photosynthetic electron flow through photosystem II is insensitive to water deficit in field‐grown G. hirsutum.  相似文献   

2.
Temperature stress including low and high temperature adversely affect the growth, development and productivity of crops. Faba bean (Vicia faba L.) is an important crop as both human food source and animal feed, which contains a range of varieties that are sensitive to cold and heat stresses. In this study, 127 faba bean genotypes were collected from gene banks based on differences in geographical origin. The 127 genotypes were treated by single cold stress (2/2 °C day/night temperature (DT/NT)) and 42 genotypes were treated by either single episode of cold or heat (38/30 °C DT/NT) stress, or a combination of both at photosynthetic photon flux density of 250 µmol m?2 s?1. Chlorophyll fluorescence was used to detect the tolerance of faba beans to low and high temperatures. The maximum quantum efficiency of photosystem II (PSII), Fv/Fm, revealed pronounced differences in cold tolerance among the faba bean genotypes. The 42 genotypes were clustered into four groups according to cold and heat stresses, respectively, and the susceptibilities of faba beans under temperature stress could be distinguished. The combination of cold and heat stresses could aggravate the damage on reproductive organs, but not on the leaves, as indicated by the Fv/Fm. These results confirm that the use of Fv/Fm is a useful approach for detecting low and high temperature damage to photosystem II and to identify tolerant faba bean genotypes, however the results also indicate that the geographical origin of the genotypes could not directly be used to predict climate resilience. These sources of cold- and heat-tolerance could improve the temperature tolerance of faba bean in breeding programs.  相似文献   

3.
Increasing productivity through improvement of photosynthesis in faba bean breeding programmes requires understanding of the genetic control of photosynthesis‐related traits. Hence, we investigated the gene action of leaf area, gas exchange traits, canopy temperature, chlorophyll content, chlorophyll fluorescence parameters and biomass. We chose inbred lines derived from cultivars 'Aurora' (Sweden) and 'Mélodie' (France) along with an Andean accession, ILB 938, crossed them (Aurora/2 × Mélodie/2, ILB 938/2 × Aurora/2 and Mélodie/2 × ILB 938/2), and prepared the six standard generations for quantitative analysis (P1, P2, F1, F2, B1, and B2). Gene action was complex for each trait, involving additive and dominance gene actions and interactions. Additive gene action was important for SPAD, photosynthetic rate, stomatal conductance and Fv/Fm. Dominance effect was important for biomass production. It is suggested that breeders selecting for productivity can maximize genetic gain by selecting early generations for canopy temperature, SPAD and Fv/Fm, then later generations for biomass. The information on genetics of various contributing traits of photosynthesis will assist plant breeders in choosing an appropriate breeding strategy for enhancing productivity in faba bean.  相似文献   

4.
This study analysed the alleviating effect of elevated CO2 on stress‐induced decreases in photosynthesis and changes in carbohydrate metabolism in two wheat cultivars (Triticum aestivum L.) of different origin. The plants were grown in ambient (400 μl l?1) and elevated (800 μl l?1) CO2 with a day/night temperature of 15/10 °C. At the growth stages of tillering, booting and anthesis, the plants were subjected to heat stress of 40 °C for three continuous days. Photosynthetic parameters, maximum quantum efficiency of photosystem II (PSII) photochemistry (Fv/Fm) and contents of pigments and carbohydrates in leaves were analysed before and during the stress treatments as well as after 1 day of recovery. Heat stress reduced PN and Fv/Fm in both wheat cultivars, but plants grown in elevated CO2 maintained higher PN and Fv/Fm in comparison with plants grown in ambient CO2. Heat stress reduced leaf chlorophyll contents and increased leaf sucrose contents in both cultivars grown at ambient and elevated CO2. The content of hexoses in the leaves increased mainly in the tolerant cultivar in response to the combination of elevated CO2 and heat stress. The results show that heat stress tolerance in wheat is related to cultivar origin, the phenological stage of the plants and can be alleviated by elevated CO2. This confirms the complex interrelation between environmental factors and genotypic traits that influence crop performance under various climatic stresses.  相似文献   

5.
Tomato cultivars differ in their sensitivity to heat stress, and the sensitivity depends on the developmental stage of the plants. It is less known how heat stress affects tomato at the anthesis stage in terms of leaf physiology and fruit set and whether the ability of tomato to tolerate heat at different developmental stages is linked. To investigate photosynthetic gas exchange characteristics, carbohydrate content and fruit set during heat stress, a thermo‐tolerant cultivar (‘LA1994’) and a thermo‐sensitive cultivar (‘Aromata’) were studied at the seedling and anthesis stage. The photosynthetic parameters, maximum quantum efficiency of photosystem II (Fv/Fm), chlorophyll content, carbohydrate content and fruit set were determined in plants grown at 26/18 °C (control) and 36/28 °C (heat stress). The physiological responses including net photosynthetic rate (PN), chlorophyll content and Fv/Fm decreased in ‘Aromata’ at both developmental stages during heat stress, whereas they were unaltered in ‘LA1994’ during heat stress as compared to the respective control. This was accompanied by lower contents of glucose and fructose in mature leaves of ‘Aromata’ at the seedling stage under heat stress. In contrast, the glucose content increased while the fructose content was unaltered in mature leaves of ‘LA1994’ at the seedling stage under heat stress. High temperature induced a similar change in carbohydrate content in the young leaves of both cultivars at anthesis. The fructose and sucrose content were unaffected in the mature leaves of ‘Aromata’ but significantly increased in ‘LA1994’ under heat stress at anthesis. The heat stress treatment decreased pollen viability and inhibited fruit set due to flower wilting and abnormal abscission in ‘Aromata’, whereas fruit set was not inhibited in ‘LA1994’. A decrease in chlorophyll content, photosynthesis and carbohydrate content in the mature leaves of tomato could be related to fruit set failure at high temperature. The results show that physiological responses to heat stress at the seedling stage correspond with the responses at the anthesis stage, demonstrating that screening for heat stress sensitivity can be carried out in young plants.  相似文献   

6.
Combined effects of temperature and light quality on plants have received little attention. We investigated the single and interactive effects of temperature and light quality on growth and physiological characteristics of four canola (Brassica napus) cultivars – Clearfield 46A76 (cv1), Clearfield 45H72 (cv2), Roundup Ready 45H24 (cv3) and Roundup Ready 45H21 (cv4). Plants were grown under lower (24°/20 °C) and higher (30°/26 °C) temperature regimes at low red/far‐red (R/FR), normal R/FR and high R/FR light ratios in environment‐controlled growth chambers (16 h light/8 h dark). Higher temperature reduced stem height and diameter; leaf number and area; dry matter of all plant parts; and specific leaf weight, but increased leaf area ratio; and chlorophyll (Chl) fluorescence (Y). Low R/FR increased stem height; Y; and ethylene, but decreased stem diameter; Fv/Fm; Chl a; Chl b; and carotenoids. Among cultivars, plants from cv4 were tallest with thickest stems and greatest dry matter. None of the main factors affected gas exchange. Higher temperature at high R/FR caused cv3 to be shortest, whereas lower temperature at low R/FR caused cv4 to be tallest. We conclude that heat and other stress factors will adversely affect sensitive crops, but tolerant genotypes should perform well under future climate.  相似文献   

7.
Drought tolerance was investigated in ‘C306’, one of the most drought tolerant wheat cultivars bred in India in the 1960’s. An intervarietal mapping population of recombinant inbred lines of the cross ‘C306’ × ‘HUW206’ was evaluated for drought tolerance components, namely potential quantum efficiency of photosystem (PS) II (Fv/Fm), chlorophyll content (Chl), flag leaf temperature (Lt), and grain yield per plant (Gyp) under stress. Three independent experiments were conducted under well-watered and water-stressed conditions in greenhouses and growth chambers at Kansas State University (USA). Five hundred and sixty microsatellite markers covering the entire genome were screened for polymorphism between the parents. A QTL (QLt.ksu-1D) for Lt (low flag leaf temperature under stress) on the short arm of chromosome 1D between markers Xbarc271 and Xgwm337 at LOD 3.5 explained 37% of the phenotypic variation. A QTL for Fv/Fm (QF v /F m .ksu-3B) and Chl (QChl.ksu-3B) controlling quantum efficiency of PS II and chlorophyll content under stress were co-localized on chromosome 3B in the marker interval Xbarc68–Xbarc101 and explained 35–40% of the phenotypic variation for each trait. A QTL (QGyp.ksu-4A) for Gyp on chromosome 4A at a LOD value of 3.2 explained 16.3% of the phenotypic variation. Inconsistent QTLs were observed for Fv/Fm on chromosomes 3A, 6A, 2B, 4B, and 4D; for Chl on 3A, 6A, 2B and 4B; and for Lt on 1A, 3A 6A, 3B and 5B. The identified QTLs give a first glimpse of the genetics of drought tolerance in C306 and need to be validated in field experiments using the marker-phenotype linkages reported here.  相似文献   

8.
Selection for drought tolerance entails prioritizing plant traits that integrate critical physiological processes occurring during crop growth. Discrimination against 13C (?) in leaflets (?leaflet) and tubers (?tuber) was compared under two water regimes in two potato‐improved varieties selected to maintain yield under drought conditions (Unica and Sarnav) and one drought susceptible European cultivar (Désirée). In the control treatment, soil water content was kept at field capacity over the whole growth cycle, while in the drought treatment water supply was restricted after tuber initiation (50 % of field capacity). Gas exchange and N content per unit leaf area (Narea) as well as ? were assessed at different stages. Sarnav showed the highest tuber yield in both water conditions, suggesting that yield in the water restriction treatment was largely driven by yield potential in this genotype. Higher stomatal conductance (gs) and Narea and lower ?leaflet in well‐watered Sarnav suggested higher photosynthetic capacity. Under water restriction, Sarnav maintained higher gs indicating that carbon diffusion was a key factor for biomass accumulation under water restriction. Our results suggest the use of ? determined after tuber initiation as an indirect selection indicator for tuber yield under both well‐watered and restricted soil water availability conditions.  相似文献   

9.
Salt (NaCl)‐induced regulation of some key physio‐biochemical characteristics in two okra (Abelmoschus esculentus L.) cultivars (Nirali and Posa Sawni) was examined under greenhouse conditions. Plants of both cultivars were subjected for 30 days to sand culture salinized with four salt levels [0 (control), 50, 100 and 150 mm NaCl] in Hoagland’s nutrient solution. Salt stress significantly reduced the shoot and root fresh weights, transpiration rate, chlorophyll b content, net CO2 assimilation (A), transpiration rate (E), while enhanced leaf and root Na+ and Cl– concentrations in both cultivars. In contrast, chlorophyll a content, stomatal conductance (gs), leaf internal CO2 (Ci), Ci/Ca ratio, water‐use efficiency (A/E) and fluorescence characteristics such as photochemical quenching (qP), non‐photochemical quenching (NPQ), efficiency of PS‐II (Fv/Fm), proline contents, and leaf and root K+, Ca2 + and N contents remained almost unaffected in both lines due to salt stress. The efficiency of PSII (Fv/Fm), A, chlorophyll b, root fresh weight and root N were higher in relatively salt tolerant cv. Nirali, whereas leaf Na+ and root Cl– were higher in cv. Posa Sawni. The relatively more reduction in growth in the cv. Posa Sawni was found to be associated with higher accumulation of Na+ in its leaves and Cl– in roots.  相似文献   

10.
Drought is one of the major factors limiting barley yields in many developing countries worldwide. The identification of molecular markers linked to genes controlling drought tolerance in barley is one way to improve breeding efficiency. In this study, we analyzed the quantitative trait loci (QTL) controlling chlorophyll content and chlorophyll fluorescence in 194 recombinant inbred lines (RILs) developed from the cross between the cultivar ‘Arta’ and Hordeum spontaneum 41-1. Five traits, chlorophyll content, and four chlorophyll fluorescence parameters, namely initial fluorescence (Fo), maximum fluorescence (Fm), variable fluorescence (Fv), and maximum quantum efficiency of PSII (Fv/Fm) which are related to the activity of the photosynthetic apparatus, were measured under well-watered and drought stress conditions at post-flowering stage. QTL analysis identified a total of nine and five genomic regions, under well-watered and drought stress conditions, respectively, that were significantly associated with the expression of the five target traits at post-flowering stage. No common QTL was detected except one for chlorophyll content, which was identified in both growth conditions, demonstrating that the genetic control of the expression of the traits related to photosynthesis differed under different water conditions. A QTL for Fv/Fm, which is related to the drought tolerance of photosynthesis was identified on chromosome 2H at 116 cM in the linkage map under drought stress. This QTL alone explained more than 15% of phenotypic variance of maximum quantum yield of PSII, and was also associated with the expression of four other traits. In addition, another QTL for Fv/Fm was also located on the same chromosome (2H) but at 135.7 cM explaining around 9% of the phenotypic variance under drought conditions. The result presented here suggest that two major loci, located on chromosome 2H, are involved in the development of functional chloroplast at post-flowering stage for drought tolerance of photosynthesis in barley under drought stress. If validated in other populations, chlorophyll fluorescence parameters could be used as selection criteria for drought tolerance.  相似文献   

11.
The main task of this research was to evaluate canopy temperature and Crop Water Stress Index (CWSI) by assessing genotype variability of maize performance for different water regimes. To that end, three hundred tropical and subtropical maize hybrids with different phenology in terms of date of anthesis were evaluated. The influence of phenology on the change in canopy temperatures and CWSI was not equal during the three dates of measurement. At the end of vegetative growth (82 days after sowing, DAS) and at the blister stage (DAS 97), a high significant difference in temperatures and CWSI (P < 0.001) were obtained between the early‐ and late‐maturity genotypes. During anthesis (DAS 89), phenology had a significant effect (P < 0.01) only for the well‐watered genotypes, while under water‐stress conditions, no differences were found between early and late genotypes in terms of canopy temperature and CWSI. High significant differences (P < 0.001) in stomatal conductance (gs) between early and late genotypes for different treatments were observed. A relationship (R2 = 0.62) between gs and canopy temperature was obtained. Under a water‐stress canopy, temperature was measured at anthesis, which was negatively correlated with grain yield of the early (r = ?0.55)‐ and late (r = ?0.46)‐maturity genotypes in the water‐stressed condition.  相似文献   

12.
The physiological functions of epicuticular wax (EW) include reflectance of irradiation and the reduction of water loss. When a plant experiences stressful conditions, most notably, high irradiance and temperature, damage to the photosynthetic apparatus can occur and is signalled by a decrease in the Fv/Fmax ratio. In this study, we examined the influence of increased EW on physiological function in terms of chlorophyll fluorescence (ChFl), stomatal conductance (gs), leaf temperature and spectral reflectance indices (SRI) of bread wheat (Triticum aestivum L.) cultivars. The wheat cultivars were subjected to high temperature stress (HT) (38–40°C) under greenhouse conditions when the primary inflorescence was fully emerged to determine its effect on leaf EW deposition. Leaf temperature depression (LTD) was generally lower in control (2.3°C—2012, 0.94°C—2013) compared to HT stress (3.13°C—2012, 4.05°C—2013). Cultivars in control (0.69 to 0.74 Fv/Fmax) had significantly higher ChFl compared to HT (0.58 to 0.74 Fv/Fmax). HT treatment resulted in higher EW (1.28—2012, 4.59 mg dm?2—2013) compared to control treatment (1.04—2012 to 4.56 mg dm?2—2013). Leaves devoid of EW showed significant variation among cultivars at reproductive stages for water index (WI), normalized phaeophytinization index (NPQI) and simple ratio index (SRI). In HT stress conditions, significant correlations were observed between EWL and SRI only at 3DAFE (days after full emergence), suggesting that increased EWL induced by HT and irradiation in early development may provide relief and prevent grain loss. EWL significantly associated with the physiological traits ChFl, gs, LTD and spike temperature depression (SpTD). These observations suggest that EWL may lessen the effect of high irradiance, thereby, effectively adjusting stomatal conductance, ChFl and leaf temperature, limiting the risk of over excitation of photosystem II.  相似文献   

13.
Wild Lens taxa are invaluable sources of useful traits for broadening genetic base of cultivated lentil. Nine inter‐sub‐specific and interspecific crosses were made successfully between cultivated (Lens culinaris ssp. culinaris) and wild lentils (L. culinaris ssp. orientalis, odemensis, lamottei and ervoides). The effect of species groups, day length and temperature on crossability in lentils was evident under normal winter sowing in New Delhi and in summer Himalayan nursery at Sangla in Himachal Pradesh, India, although pollen fertility assessed in all the cross‐combinations showed no significant variation. True hybridity of nine inter‐sub‐specific and interspecific crosses was confirmed through morphological and molecular (ISSR) markers, in which three of 120 primers could confirm the hybridity of all the crosses. All cross‐combinations were also studied for important quantitative traits related to yield. The range, mean and coefficient of variation were estimated in parental lines, F1 and F2 generations to determine the extent of variability generated in cultivated lentils through the introgression of genes from wild L. taxa. A high level of heterosis was observed in F1 crosses for important traits studied. Substantially higher variations for seed yield and its attributing traits were exhibited in F2 generations indicating transgressive segregation. The results of the present investigation revealed that wild L. taxa can be successfully exploited for lentil improvement programmes, and the variations generated could be easily utilized for broadening the genetic base of cultivated lentil gene pool for improving the yield as well as wider adaptation.  相似文献   

14.
Winter‐hardiness is a complex trait limiting cultivation of winter barley (Hordeum vulgare ssp. vulgare) with respect to the regions of temperate climate. In the present studies, we verified whether inexpensive and fast physiological markers characterizing photosynthetic acclimation to cold may provide robust characteristics of winter barley genotypes for improved frost resistance. Freezing tolerance of 28 winter barley varieties and advanced breeding lines were tested for three winters in field‐laboratory experiment and under fully controlled conditions. To increase the environmental variability of freezing tolerance, a part of the plants were also de‐acclimated under semi‐controlled conditions and re‐acclimated in laboratory before freezing tests. After controlled cold acclimation, apparent quantum yield of photosystem II (Fv/Fm) as well as photochemical (qP) and non‐photochemical (NPQ) coefficients of chlorophyll fluorescence quenching were studied. Field‐laboratory method assessment of freezing tolerance gives distinct and even opposite results in subsequent years. Also de‐acclimation interacted with growth conditions in the field, giving different rankings of genotypes each year. The results obtained suggest that high level of freezing tolerance measured in laboratory, which is connected with photosynthetic acclimation to cold may be not sufficient for the expression of field resistance, especially when winter conditions are not favourable for cold acclimation.  相似文献   

15.
Soybean mosaic virus (SMV) can cause serious yield losses in soybean. Soybean cultivar ‘RN‐9’ is resistant to 15 of 21 SMV strains. To well‐characterize this invaluable broad‐spectrum SMV‐resistance, populations (F1, F2 and F2:3) derived from resistant (R) × susceptible (S) and R × R crosses were tested for SMV‐SC18 resistance. Genetic analysis revealed that SC18 resistance in ‘RN‐9’ plus two elite SMV‐resistant genotypes (‘Qihuang No.1’ and ‘Kefeng No.1’) are controlled by independently single dominant genes. Linkage analysis showed that the resistance of ‘RN‐9’ to SMV strains SC10, SC14, SC15 and SC18 is controlled by more than one gene(s). Moreover, Rsc10‐r and Rsc18‐r were both positioned between the two simple sequence repeats markers Satt286 and Satt277, while Rsc14‐r was fine‐mapped in 136.8‐kb genomic region containing sixteen genes, flanked by BARCSOYSSR_06_0786 and BARCSOYSSR_06_0790 at genetic distances of 3.79 and 4.14 cM, respectively. Allelic sequence comparison showed that Cytochrome P450‐encoding genes (Glyma.06g176000 and Glyma.06g176100) likely confer the resistance to SC14 in ‘RN‐9’. Our results would facilitate the breeding of broad‐spectrum and durable SMV resistance in soybeans.  相似文献   

16.
强光高温同时作用下不同小麦品种的光合特性   总被引：10，自引：1，他引：9  
齐学礼  胡琳  董海滨  张磊  王根松  高崇  许为钢 《作物学报》2008,34(12):2196-2201
以小麦品种藁城8901、豫麦49、郑麦9405、周18为试材,用强光(1 900 μmol m-2 s-1)、高温(35℃)同时处理材料3 h,研究了高光强和高温共同合胁迫对小麦旗叶光合作用和叶绿素荧光特性的影响。结果表明,正常生长条件下,郑麦9405和周18的光饱和速率、饱和光强均高于藁城8901和豫麦49,郑麦9405的表观量子效率也最高。强光高温处理使藁城8901、豫麦49和周18的光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、胞间CO2浓度(Ci)较对照大幅下降;郑麦9405的Pn、Gs也出现了下降,但降幅最小,Pn仍保持11.6 μmol CO2 m-2 s-1,Tr较对照略有上升;4种基因型小麦的Ci未较对照明显变化;与对照相比,4个材料的最大光量子效率(Fv/Fm)、开放的光系统II反应中心的激发能捕获效率(Fv’/Fm’)、作用光下光系统II的实际量子效率(ФPSII)、光化学猝灭系数(qP)均下降,而非光化学猝灭系数(NPQ)大幅上升;其中郑麦9405的各项荧光参数均较高。研究表明,小麦旗叶对强光高温的适应性存在品种间差异,郑麦9405的耐强光高温特性优于其他3品种;强光高温下较高的蒸腾速率和较大的NPQ可能是郑麦9405维持光合机构功能的重要原因。  相似文献   

17.
In pepper (Capsicum annuum), the major genes (R‐genes) Me1 and Me3 confer resistance against root‐knot nematodes (Meloidogyne spp.). The combination of R‐genes and quantitative resistance factors in the same genotype is considered a good breeding strategy for increasing the durability of R‐genes. To ascertain this hypothesis, five pepper inbred lines, differing in their quantitative resistance level, were combined with Me1 or Me3 genes in F1 hybrids. The resistance of inbred lines and F1 hybrids was evaluated in a greenhouse with soil naturally infected by M. incognita in two successive growing years. In both years, lines carrying Me3 were less infected by the nematode when combined with quantitative resistance. An increase in nematode infection was observed in the second growing year in lines carrying Me1 or Me3, independently of quantitative resistance. The infection level recorded in inbred lines without R‐genes was similar in both years. The effectiveness of quantitative resistance controlling M. incognita is confirmed in greenhouse conditions, although the durability of Me1 and Me3 when combined with quantitative resistance factors was not seen to increase.  相似文献   

18.
Cold tolerance is a complex trait, and QTL pyramiding is required for rice breeding. In this study, a total of seven QTLs for cold tolerance in the Japonica rice variety ‘Nipponbare’ were identified in an F2:3 population. A stably inherited major QTL, called qCTS11, was detected in the region adjacent to the centromere of chromosome 11. In a near‐isogenic line population, the QTL was further dissected into two linked loci, qCTS11.1 and qCTS11.2. Both of the homozygous alleles of qCTS11.1 and qCTS11.2 from ‘Nipponbare’ showed major positive effects on cold tolerance. Through pyramiding the linked QTLs in the cold‐sensitive Indica rice cultivar ‘93‐11’, we have developed a new elite, high‐yielding Indica variety with cold tolerance.  相似文献   

19.
陆地棉苗期耐盐性的高效鉴定方法   总被引：5，自引：0，他引：5  
利用2个耐盐和2个盐敏感的陆地棉品种,分别设置对照和4% (40 g L–1)浓度NaCl溶液处理三叶期幼苗,处理72 h后调查盐害指数,测定地上部分鲜重、根鲜重、叶片相对含水量、叶绿素荧光参数、相对电导率、丙二醛含量、抗氧化酶类活性等13个与耐盐性相关的重要指标。利用灰色关联聚类、主成分分析和逐步回归等方法综合评价陆地棉苗期耐盐性,认为最大光化学效率(Fv/Fm)可以作为鉴定陆地棉苗期耐盐性的关键指标,构建耐盐指数(y)方程y = 1.943x – 0.882,(x = 最大光化学效率),同时结合另外2个耐盐和2个盐敏感品种所得方程y值对耐盐等级进行划分。进一步利用23个已知耐盐性的品种检验方程,计算结果与田间鉴定结果完全一致。因此选用最大光化学效率作为唯一指标鉴定陆地棉苗期耐盐性,高效准确,同时通过构建方程和划分耐盐等级,为未来大规模陆地棉品种资源耐盐性鉴定提供技术标准和研究基础。  相似文献   

20.
A field‐experiment (2004/2005 and 2005/2006 seasons) was conducted in the coastal plain of south‐eastern Sicily (37°03′N, 15°18′E, 15 m a.s.l.), on a Calcixerollic Xerochrepts soil, aimed at quantifying the effect of shading on chlorophyll (Chl) content, Chl fluorescence, photosynthesis and growth of subterranean clover. Four levels of photosynthetically active radiation reduction (from 0 % to 90 %) were tested on Trifolium brachycalycinum cv. ‘Clare’ and Trifolium subterraneum ecotype ‘Ragalna’. In both species shading progressively increased Fv/Fm, internal CO2 concentration, diffusive leaf resistance and specific leaf area (up to 8 %, 34 %, 18 % and 68 %, respectively), and decreased Chl content, Tmax, photosynthetic rate and plant dry weight (up to 9 %, 24 %, 79 % and 39 %, respectively). As plants aged, characteristic bell‐shaped trends were evident for photosynthetic parameters, with Fv/Fm increasing up until the onset of flowering, and thereafter declining. This implies that Fv/Fm may be a useful indicator of earliness in subterranean clover genotypes. The aboveground dry biomass response to shading was both genotype‐ and season‐dependent, but was predictable from the measurement of relative leaf Chl content. Moreover, our results suggest that an improvement in the interaction between host‐rhizobium may represent a major potential breeding target for enhancing subterranean clover tolerance to shading.  相似文献   

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