2种玉米幼苗耐旱性生理机制研究

以白种皮(白玉米)和黄种皮(黄玉米)2个玉米栽培品种为材料,在水培条件下进行聚乙二醇(PEG-6000)模拟干旱胁迫处理,分析玉米叶片抗旱性相关生理特性和质膜H+-ATP酶活性的变化,探讨2种玉米幼苗耐旱性生理机制。结果表明:(1)在2%、5%、10%PEG-6000处理条件下,随处理浓度和时间的增加,2种玉米幼苗植株失水率上升,叶片蒸腾速率降低,气孔传导率下降;在所有相同处理条件下,白玉米植株失水率明显小于黄玉米,而叶片蒸腾速率和气孔传导率下降幅度明显大于黄玉米,即白玉米的耐旱性比黄玉米强。(2)在相同浓度PEG-6000处理下,白玉米叶片可溶性蛋白、可溶性糖含量、游离脯氨酸含量均高于黄玉米,它在干旱胁迫下的渗透调节能力强于黄玉米。(3)在抗氧化酶体系中,随着PEG-6000胁迫浓度的升高,2种玉米叶片CAT活性呈下降趋势,但白玉米CAT活性在2%和5%PEG-6000胁迫下均显著高于黄玉米,其叶片中H2O2含量显著低于黄玉米。(4)随着PEG-6000胁迫浓度的升高,白玉米叶片质膜H+-ATPase磷酸化水平及其与14-3-3蛋白的结合受到的抑制作用比黄玉米强,白玉米叶片质膜H+-ATPase活性比黄玉米叶片低,叶片气孔开度小于黄玉米,叶片蒸腾速率和气孔传导率均低于黄玉米,这可能是白玉米耐旱性强于黄玉米的一个重要机制。     

褪黑素对玉米幼苗根系发育和抗旱性的影响

褪黑素是一种在生物体内广泛存在的吲哚胺类化合物,参与植物的多种生理和生化过程.近年来研究认为褪黑素可以不同程度地增强植物的抗逆性,但对其作用机理仍知之甚少.通过两种褪黑素的施用方法,详细研究了褪黑素对于玉米根系发育和抗旱性的影响.首先,采用水培根灌褪黑素的方法对玉米幼苗的根系和生长状况进行分析,结果表明施加褪黑素显著提...     

Drought Tolerance in Mung Bean is Associated with the Genotypic Divergence,Regulation of Proline,Photosynthetic Pigment and Water Relation

Drought is one of the critical conditions for the growth and productivity of many crops including mung bean (Vigna radiata L. Wilczek). Screening of genotypes for variations is one of the suitable strategies for evaluating crop adaptability and global food security. In this context, the study investigated the physiological and biochemical responses of four drought tolerant (BARI Mung-8, BMX-08010-2, BMX-010015, BMX-08009-7), and four drought sensitive (BARI Mung-1, BARI Mung-3, BU Mung-4, BMX-05001) mung bean genotypes under wellwatered (WW) and water deficit (WD) conditions. The WW treatment maintained sufficient soil moisture (22% ± 0.5%, i.e., 30% deficit of available water) by regularly supplying water. Whereas, the WD treatment was maintained throughout the growing period, and water was applied when the wilting symptom appeared. The drought tolerant (DT) genotypes BARI Mung-8, BMX-08010-2, BMX-010015, BMX-08009-7 showed a high level of proline accumulation (2.52–5.99 mg g⁻¹ FW), photosynthetic pigment (total chlorophyll 2.96–3.27 mg g⁻¹ FW at flowering stage, and 1.62–2.38 mg g⁻¹ FW at pod developing stage), plant water relation attributes including relative water content (RWC) (82%–84%), water retention capacity (WRC) (12–14) as well as lower water saturation deficit (WSD) (19%–23%), and water uptake capacity (WUC) (2.58–2.89) under WD condition, which provided consequently higher relative seed yield. These indicate that the tolerant genotypes gained better physiobiochemical attributes and adaptability in response to drought conditions. Furthermore, the genotype BMX- 08010-2 showed superiority in terms of those physio-biochemical traits, susceptibility index (SSI) and stress tolerance index (STI) to other genotypes. Based on the physiological and biochemical responses, the BMX-08010-2 was found to be a suitable genotype for sustaining yield under drought stress, and subsequently, it could be recommended for crop improvement through hybridization programs. In addition, the identified traits can be used as markers to identify tolerant genotypes for drought-prone areas.     

干旱胁迫对苗木蒸腾耗水的影响

采用Lico-6400便携式光合系统测定仪和BP3400精密天平等仪器研究了9个北方主要造林树种的蒸腾速率及实际蒸腾耗量;用压力室法分阶段测定了苗木的叶水势。得出了苗木在正常水分条件下及干旱胁迫过程中的蒸腾耗水规律。比较分析了不同水势梯度下、昼夜不同时间段的各树种的蒸腾耗水量及蒸腾耗水速率。结果表明,蒸腾耗水以白天为主,在相同的水分条件下,不同的苗木有不同的蒸腾耗水量,同种苗木的蒸腾耗水量随干旱胁迫的加重而减少,在受到严重干旱胁迫时,针叶树油松和侧柏的耗水量均降至正常水分条件下的11.7%,阔叶乔木树种降至6．6％,灌木树种降至16．9％。通过研究苗木在不同水势梯度下的耗水特性和蒸腾耗水量。为在水量缺乏的情况下,进行有效的林木培育和植被恢复重建提供依据。     

Molecular Improvement of Tropical Maize for Drought Stress Tolerance in Sub-Saharan Africa

The C4 grass Zea mays (maize or corn) is the third most important food crop globally after wheat and rice in terms of production and the second most widespread genetically modified (GM) crop, after soybean. Its demand is predicted to increase by 45% by the year 2020. In sub-Saharan Africa, tropical maize has traditionally been the main staple of the diet, 95% of the maize grown is consumed directly as human food and as an important source of income for the resource—poor rural population. However, its growth, development and production are greatly affected by environmental stresses such as drought and salinization. In this respect, food security in tropical sub-Saharan Africa is increasingly dependent on continuous improvement of tropical maize through conventional breeding involving improved germplasm, greater input of fertilizers, irrigation, and production of two or more crops per year on the same piece of land. Integration of advances in biotechnology, genomic research, and molecular marker applications with conventional plant breeding practices opens tremendous avenues for genetic modifications and fundamental research in tropical maize. The ability to transfer genes into this agronomically important crop might enable improvement of the species with respect to enhanced characteristics, such as enriched nutritional quality, high yield, resistance to herbicides, diseases, viruses, and insects, and tolerance to drought, salt, and flooding. These improvements in tropical maize will ultimately enhance global food production and human health. Molecular approaches to modulate drought stress tolerance are discussed for sub-Saharan Africa, but widely applicable to other tropical genotypes in Central and Latin America. This review highlights abiotic constraints that affect growth, development and production of tropical maize and subsequently focuses on the mechanisms that regulate drought stress tolerance in maize. Biotechnological approaches to manage abiotic stress tolerance in maize will be discussed. The current status of tropical maize transformation using Agrobacterium as a vehicle for DNA transfer is emphasized. This review also addresses the present status of genetically modified organisms (GMOs) regulation in sub-Saharan Africa.     

Large Root Cortical Cell Size Improves Drought Tolerance in Maize

The objective of this study was to test the hypothesis that large cortical cell size (CCS) would improve drought tolerance by reducing root metabolic costs. Maize (Zea mays) lines contrasting in root CCS measured as cross-sectional area were grown under well-watered and water-stressed conditions in greenhouse mesocosms and in the field in the United States and Malawi. CCS varied among genotypes, ranging from 101 to 533 µm². In mesocosms, large CCS reduced respiration per unit of root length by 59%. Under water stress in mesocosms, lines with large CCS had between 21% and 27% deeper rooting (depth above which 95% of total root length is located in the soil profile), 50% greater stomatal conductance, 59% greater leaf CO₂ assimilation, and between 34% and 44% greater shoot biomass than lines with small CCS. Under water stress in the field, lines with large CCS had between 32% and 41% deeper rooting (depth above which 95% of total root length is located in the soil profile), 32% lighter stem water isotopic ratio of ¹⁸O to ¹⁶O signature, signifying deeper water capture, between 22% and 30% greater leaf relative water content, between 51% and 100% greater shoot biomass at flowering, and between 99% and 145% greater yield than lines with small cells. Our results are consistent with the hypothesis that large CCS improves drought tolerance by reducing the metabolic cost of soil exploration, enabling deeper soil exploration, greater water acquisition, and improved growth and yield under water stress. These results, coupled with the substantial genetic variation for CCS in diverse maize germplasm, suggest that CCS merits attention as a potential breeding target to improve the drought tolerance of maize and possibly other cereal crops.Suboptimal water availability is a primary constraint for terrestrial plants and a primary limitation to crop production. In developing countries, the problem of yield loss due to drought is most severe (Edmeades, 2008, 2013), and the problem will be further exacerbated in the future due to climate change (Burke et al., 2009; Schlenker and Lobell, 2010; Lobell et al., 2011a; IPCC, 2014; St. Clair and Lynch, 2010). The development of drought-tolerant crops is therefore an important goal for global agriculture. Breeding for drought adaptation using yield as a selection criterion is generally not efficient, since yield is an integration of complex mechanisms at different levels of organization affected by many elements of the phenotype and the environment interacting in complex and often unknown ways. Trait-based selection or ideotype breeding is generally a more efficient selection strategy, permitting the identification of useful sources of variation among lines that have poor agronomic adaptation, elucidation of genotype-environment interactions, and informed trait stacking (Lynch, 2007; Araus et al., 2008; Richards et al., 2010; Wasson et al., 2012; York et al., 2013; Lynch, 2014).Under drought stress, plants allocate more resources to root growth relative to shoot growth, which can enhance water acquisition (Sharp and Davies, 1979; Palta and Gregory, 1997; Lynch and Ho, 2005). The metabolic costs of soil exploration by root systems are significant and can exceed 50% of daily photosynthesis (Lambers et al., 2002). With a large root system, each unit of leaf area has more nonphotosynthetic tissue to sustain, which may reduce productivity by diverting resources from shoot and reproductive growth (Smucker, 1993; Nielsen et al., 2001; Boyer and Westgate, 2004). Genotypes with less costly root tissue could develop the extensive, deep root systems required to fully utilize soil water resources in drying soil without as much yield penalty. Therefore, root phenes that reduce the metabolic costs of soil exploration, thereby improving water acquisition, are likely to be valuable for improving drought tolerance (Lynch and Ho, 2005; Zhu et al., 2010; Lynch, 2011; Richardson et al., 2011; Jaramillo et al., 2013; Lynch 2014).Maize (Zea mays) is the principal global cereal. Maize production is facing major challenges as a result of the increasing frequency and intensity of drought (Tuberosa and Salvi, 2006), and this problem will likely be exacerbated by climate change (Lobell et al., 2011b). The Steep, Cheap, and Deep ideotype has been proposed for improving water and nitrogen acquisition by maize when these resources are limited (Lynch, 2013). This ideotype consists of root architectural, anatomical, and physiological traits that may increase rooting depth and thereby improve water acquisition from drying soils. Anatomical phenes could influence the metabolic cost of soil exploration by changing the proportion of respiring and nonrespiring root tissue and affecting the metabolic cost of tissue construction and maintenance, which is an important limitation to root growth and plant development under edaphic stress. Specific anatomical phenes that may contribute to rooting depth by reducing root metabolic costs include components of living cortical area (LCA; Jaramillo et al., 2013), including root cortical aerenchyma (RCA), cortical cell size (CCS), and cortical cell file number (Lynch, 2013).RCA consists of large air-filled lacunae that replace living cortical cells as a result of programmed cell death (Evans, 2004). Previous studies have demonstrated that RCA improves crop adaptation to edaphic stress by reducing the metabolic cost of soil exploration and exploitation (Fan et al., 2003; Zhu et al., 2010; Postma and Lynch, 2011a, Saengwilai et al., 2014a). RCA is associated with a disproportionate reduction of root respiration, thereby permitting greater root growth and acquisition of soil resources (Fan et al., 2003; Zhu et al., 2010). SimRoot modeling indicated that RCA can substantially increase the acquisition of nitrogen, phosphorus, and potassium in maize by reducing respiration and the nutrient content of root tissue (Postma and Lynch, 2011b). Under water stress in the field, maize genotypes with more RCA had deeper roots, better leaf water status, and 800% greater yield than genotypes with less RCA (Zhu et al., 2010). Under nitrogen stress in the field and in greenhouse mesocosms, maize genotypes with more RCA had greater rooting depth, greater nitrogen capture from deep soil strata, greater nitrogen content, greater leaf photosynthesis, greater biomass, and greater yield (Saengwilai et al., 2014a).LCA refers to the living portion of the cortex that remains after the formation of aerenchyma (Jaramillo et al., 2013). Recently, we reported that LCA is an important determinant of root metabolic cost and a better predictor of root respiration than RCA (Jaramillo et al., 2013). In that study, maize lines contrasting in LCA were grown under well-watered or water-stressed conditions in soil mesocosms, and LCA was associated with a reduction of specific root respiration. These results provided the impetus to investigate the relative contribution of each component of LCA to metabolic cost. Our focus here is on root CCS.Plant cell size varies substantially both among and within species (Sugimoto-Shirasu and Roberts, 2003). Cell size in a given species and tissue is under genetic control and results from the coordinated control of cell growth and cell division (Sablowski and Carnier Dornelas, 2014). The increased volume of individual cells is attributable to cytoplasmic growth and cell expansion (Marshall et al., 2012; Chevalier et al., 2014). Cytoplasmic growth is the net accumulation of macromolecules and cellular organelles, while cell expansion refers to increased cell volume caused by enlargement of the vacuole (Taiz, 1992; Sablowski and Carnier Dornelas, 2014). Lynch (2013) proposed that large CCS would decrease the metabolic costs of root growth and maintenance, both in terms of the carbon cost of root respiration and the nutrient content of living tissue, by increasing the ratio of vacuolar to cytoplasmic volume.The objective of this study was to test the hypothesis that large CCS would reduce specific root respiration (i.e. respiration per unit of root length), which under water stress would result in greater root growth, greater acquisition of subsoil water, better plant water status, and improved plant growth and yield. Diverse sets of genotypes (including landraces and recombinant inbred lines [RILs]) contrasting for CCS were evaluated under water stress and well-watered conditions in soil mesocosms in controlled environments, in the field in the United States using automated rainout shelters, and in the field in Malawi. Our results demonstrate that substantial variation for CCS exists in maize and that this variation has substantial effects on the metabolic cost of soil exploration and thereby water acquisition under drought.     

Reduced Root Cortical Cell File Number Improves Drought Tolerance in Maize

We tested the hypothesis that reduced root cortical cell file number (CCFN) would improve drought tolerance in maize (Zea mays) by reducing the metabolic costs of soil exploration. Maize genotypes with contrasting CCFN were grown under well-watered and water-stressed conditions in greenhouse mesocosms and in the field in the United States and Malawi. CCFN ranged from six to 19 among maize genotypes. In mesocosms, reduced CCFN was correlated with 57% reduction of root respiration per unit of root length. Under water stress in the mesocosms, genotypes with reduced CCFN had between 15% and 60% deeper rooting, 78% greater stomatal conductance, 36% greater leaf CO₂ assimilation, and between 52% to 139% greater shoot biomass than genotypes with many cell files. Under water stress in the field, genotypes with reduced CCFN had between 33% and 40% deeper rooting, 28% lighter stem water oxygen isotope enrichment (δ¹⁸O) signature signifying deeper water capture, between 10% and 35% greater leaf relative water content, between 35% and 70% greater shoot biomass at flowering, and between 33% and 114% greater yield than genotypes with many cell files. These results support the hypothesis that reduced CCFN improves drought tolerance by reducing the metabolic costs of soil exploration, enabling deeper soil exploration, greater water acquisition, and improved growth and yield under water stress. The large genetic variation for CCFN in maize germplasm suggests that CCFN merits attention as a breeding target to improve the drought tolerance of maize and possibly other cereal crops.Drought is a primary constraint to global crop production (Schmidhuber and Tubiello, 2007), and global climate change is likely to increase the risk of drought, especially in rain-fed agriculture (Battisti and Naylor, 2009; Burke et al., 2009; Mishra and Cherkauer, 2010; Lobell et al., 2011). Therefore, the development of crops with greater drought tolerance is an important global objective. Yield under drought is often not an efficient selection criterion in drought breeding programs, since yield is affected by many elements of the phenotype and the environment, interacting in complex and often unknown ways. Trait-based selection or ideotype breeding is generally a more efficient selection strategy, permitting the identification of useful sources of variation among lines that have poor agronomic adaptation, elucidation of genotype-by-environment interactions, and informed trait stacking (Araus et al., 2002, 2008; Manschadi et al., 2006; Lynch, 2007b, 2011; York et al., 2013).In most agroecosystems, the topsoil dries before the subsoil as drought progresses. In such environments, plants with deeper roots are able to acquire water available in deeper soil domains that may not be available to plants with shallower roots (Ludlow and Muchow, 1990; Ho et al., 2005; Hammer et al., 2009). An ideotype has been proposed to guide the breeding of crops with deeper roots and, therefore, greater water acquisition from drying soil, called Steep, Cheap, and Deep, integrating architectural, anatomical, and physiological phenes (Lynch, 2013). The term Cheap denotes phenes that reduce the metabolic cost of soil exploration, which is an important limitation to the acquisition of scarce soil resources, including water in dry soil (Fan et al., 2003; Lynch, 2007b; Zhu et al., 2010; Postma and Lynch, 2011a, 2011b; Jaramillo et al., 2013). Plant resource allocation to root growth typically increases under drought to enhance water acquisition; therefore, the metabolic cost of root growth becomes a significant component of plant fitness and adaptation under drought (Lynch, 2007b, 2013). Therefore, a plant that is able to access water in deep soil domains at reduced metabolic cost will have superior productivity, because it will have more metabolic resources available for further resource acquisition, growth, and reproduction. Evidence in support of this hypothesis comes from empirical and modeling studies for maize (Zea mays) under water and edaphic stress (Lynch, 2007a; Zhu et al., 2010; Postma and Lynch, 2011a, 2011b; Jaramillo et al., 2013).Root cortical aerenchyma (RCA) is the enlarged air space in the root cortex that forms either through cell death or cell separation (Evans, 2004). RCA is associated with a disproportionate reduction of root respiration in maize by converting living cortical tissue to air volume (Fan et al., 2003; Zhu et al., 2010). Reduction of root metabolic costs permits more internal resources to be allocated to greater root growth and, consequently, greater soil resource acquisition. RCA formation is also associated with a reduction of phosphorus content in root tissue on a volume basis, since air spaces do not contain phosphorus (Fan et al., 2003), and with improved growth in low-phosphorus soil (Lynch, 2011). RCA also reduces the nitrogen content of root tissue and is beneficial for nitrogen capture and maize growth on low-nitrogen soils (Saengwilai, 2014a). Modeling studies suggest that RCA improves crop adaptation to suboptimal nutrient availability by reducing the metabolic costs of soil exploration (Postma and Lynch, 2011a, 2011b). Under drought, Zhu et al. (2010) found that maize genotypes with more RCA had five times greater biomass and eight times greater yield than genotypes with less RCA. Living cortical area (LCA) is total transverse root cortical area minus RCA area. Jaramillo et al. (2013) found that root respiration is positively correlated with LCA, and a 3.5-fold reduction in LCA is associated with a 2.5-fold improvement in plant growth under drought. These results indicate that the metabolic demand of living cortical tissue is a primary determinant of root growth, soil exploration, and resource acquisition in soil environments with suboptimal resource availability.This study builds on earlier studies indicating that substantial reduction of root metabolic cost is associated with variation in LCA. The cortex of the maize root is composed of several concentric layers of parenchyma cells, the number of which we refer to as the cortical cell file number (CCFN). Recently, Burton et al. (2013) reported that there is 3-fold variation for CCFN in Zea spp. In that study, the variation was wider in maize landraces (six to 16 cell files) than in wild Zea spp. (seven to 13 cell files). It has been proposed that reduced CCFN would decrease the metabolic costs of root growth and maintenance, in terms of both the carbon cost of root respiration and the nutrient content of living tissue, by reducing the proportion of root volume occupied by living cortical tissue, which has greater metabolic demands than the stele (Lynch, 2013). However, the physiological utility of CCFN has not been explored.The objective of this study was to test the hypothesis that reduced CCFN would reduce root respiration, permitting greater rooting depth, thereby enhancing water acquisition and improving both plant growth and yield under water stress.     

干旱胁迫对不同耐旱性大麦品种叶片超微结构的影响

选用耐旱性不同的3个大麦(Hordeum sativum)品种作为研究对象, 分析干旱胁迫对其叶肉细胞叶绿体、线粒体和细胞核超微结构的影响。结果表明, 3个大麦品种在非胁迫条件下其超微结构无明显差异。遭受干旱胁迫后, 不耐旱大麦品种Moroc9-75叶片细胞核中染色质的凝聚程度高, 叶绿体变形, 外被膜出现较大程度的波浪状和膨胀, 同时基粒出现弯曲、膨胀、排列混乱的现象; 线粒体外形及膜受到破坏、内部嵴部分消失等。耐旱大麦品种HS41-1叶片细胞中染色质虽出现凝聚, 但凝聚程度低; 其叶绿体及线粒体与非胁迫条件下基本相似, 多数未见明显损伤。耐旱中等的大麦品种Martin叶片超微结构的变化则介于二者之间。因此, 干旱胁迫下叶绿体外形、基粒和基质类囊体膜结构的完整性与基粒的排列次序、染色质的凝聚度和线粒体膜及嵴的完整性与大麦的耐旱性相关, 这些特性可作为评价大麦耐旱性强弱的形态结构指标。     

抗氧化系统在热激诱导的玉米幼苗耐热性形成中的作用

玉米幼苗经过42℃热激4h并恢复4h后,显著提高了玉米幼苗在高温处理下的存活率。热激并恢复4h后,不同程度地提高了抗氧化酶系统过氧化氢酶(CAT),超氧化物歧化酶(SOD),谷胱甘肽还原酶(GR),抗坏血酸过氧化物酶(APX)和过氧化物酶(GPX)的活性以及抗氧化剂还原型抗坏血酸(ASA)和谷胱甘肽(GSH)的含量,且经过热激的玉米幼苗在高温处理期间及其后的恢复过程中均能保持相对较高的抗氧化酶活性和抗氧化剂水平,说明保持较高的抗氧化酶活性和抗氧化剂水平是热激诱导的玉米幼苗耐热性形成的生理基础之一。     

喀斯特土壤上香樟幼苗接种不同AM真菌后的耐旱性效应

为探索喀斯特土壤适生植物香樟幼苗在接种不同AM真菌后的耐旱适应性,进行了香樟幼苗接种幼套球囊霉(Glomus etunicatum)和层状球囊霉(Glomus lamellosum)后水分胁迫处理试验。结果表明：（1）接种AM真菌显著提高了香樟幼苗的生物量积累,AM促进植株生物量效应依次为中度>轻度>正常>重度,同一水分胁迫处理下生物量幼套球囊霉>层状球囊霉。（2）中度干旱下香樟幼苗菌根依赖性最大,幼套球囊霉接种植株的菌根依赖性较层状球囊霉大。（3）接种AM真菌显著提高了植株叶片可溶性糖、可溶性蛋白质和脯氨酸含量,并降低了丙二醛含量;在正常供水下植株叶片可溶性糖、可溶性蛋白质和脯氨酸含量层状球囊霉接种>幼套球囊霉接种>对照,干旱胁迫下表现为幼套球囊霉接种>层状球囊霉接种>对照;干旱胁迫下的幼套球囊霉接种植株丙二醛含量低于层状球囊霉接种植株。（4）总体上,可溶性糖与脯氨酸相关性极显著,可溶性蛋白质与丙二醛之间呈显著负相关性。幼套球囊霉接种香樟幼苗的耐旱性高于和层状球囊霉接种香樟幼苗。     

干旱胁迫对不同耐旱性大麦品种叶片超微结构的影响

选用耐旱性不同的3个大麦（Hordeum sativum）品种作为研究对象,分析干旱胁迫对其叶肉细胞叶绿体、线粒体和细胞核超微结构的影响。结果表明,3个大麦品种在非胁迫条件下其超微结构无明显差异。遭受干旱胁迫后,不耐旱大麦品种Moroc9-75叶片细胞核中染色质的凝聚程度高,叶绿体变形,外被膜出现较大程度的波浪状和膨胀,同时基粒出现弯曲、膨胀、排列混乱的现象;线粒体外形及膜受到破坏、内部嵴部分消失等。耐旱大麦品种HS41-1叶片细胞中染色质虽出现凝聚,但凝聚程度低;其叶绿体及线粒体与非胁迫条件下基本相似,多数未见明显损伤。耐旱中等的大麦品种Martin叶片超微结构的变化则介于二者之间。因此,干旱胁迫下叶绿体外形、基粒和基质类囊体膜结构的完整性与基粒的排列次序、染色质的凝聚度和线粒体膜及嵴的完整性与大麦的耐旱性相关,这些特性可作为评价大麦耐旱性强弱的形态结构指标。     

干旱对白皮松幼苗针叶生理特性的影响

试验目的是研究栽植前和栽植后干旱致使白皮松（Pinus bungeana Zucc.）针叶的生理特性的改变,了解白皮松造林前后能够适应的干旱范围,为白皮松科学造林提供理论依据。试验中模拟白皮松容器苗造林前后可能遇到的干旱胁迫,研究栽植前容器苗分别为B1：75%～80%（正常浇水）、B2：55%～60%（轻度干旱）、B3：35%～40%（严重干旱）和栽植后土壤相对含水量分别为A1：75%～80%、A2：55%～60%、A3：35%～40%、A4：15%～20%（极严重干旱）对白皮松针叶的生理指标的影响。结果表明：栽植前白皮松容器苗经B3处理后,针叶电解质渗透率增加,叶绿素含量和PSII最大光化学效率（Fv/Fm）显著降低,表明针叶受到一定伤害。栽植后如果正常浇水,这些影响将消除,如果遭遇栽植后干旱,B3处理的受害程度不比B1和B2处理深。栽植后白皮松经A3和A4处理4周后,针叶的电解质渗透率增加,Fv/Fm降低,表明白皮松针叶受到伤害。白皮松容器苗造林在栽植前遭到适当干旱胁迫时不会影响造林后的表现。但应避免栽植后初期4周以上严重干旱胁迫。     

Exogenous Melatonin Achieves Drought Tolerance by Improving Photosynthesis in Maize Seedlings Leaves

Russian Journal of Plant Physiology - The beneficial roles of melatonin in plants have been widely reported, but its effect on photosynthesis under drought stress is not clear. In the study,...     

Combined Role of ACC Deaminase Producing Bacteria and Biochar on Cereals Productivity under Drought

Most of the cereal crops are widely cultivated to fulfil the humans food requirements. Under changing climate scenario, the intensity of drought stress is continuously increasing that is adversely affecting the growth and yield of cereal crops. Although the cereals can tolerate moderate drought to some extent, but mostly they are susceptible to severe drought stress. Higher biosynthesis of ethylene under drought stress has been reported. Many scientists observed that inoculation of 1-aminocyclopropane-1-carboxylate (ACC) deaminase producing plant growth promoting rhizobacteria (PGPR) is an efficacious tool to overcome this problem. These PGPR secrete ACC deaminase which cleavage the ACC into the compounds, other than ethylene. Furthermore, secretion of growth hormones also play imperative role in enhancing the growth of the cereals under limited availability of water. In addition, the use of biochar has also been recognized as another effective amendment to grant resistance against drought. Biochar application improves the soil physiochemical attributes i.e., porosity, nutrients retention and water holding capacity which decrease the loss of water and increase its bioavailability. In recent era, the idea of coapplication of ACC deaminase producing PGPR and biochar is becoming popular which might be more efficient to use water under drought stress. The aim of current review is to combine the facts and understanding of this novel idea to grant maximum resistance to crops against drought stress. Some scientists have observed significant improvement in yield of cereal crops by combined use of ACC deaminase producing PGPR and biochar. However, more research is suggested for deep understanding of complex synergistic mechanism of ACC deaminase activity in combination with biochar.     

NaCl胁迫增强杂交酸模(Rumex K-1)幼苗叶片光系统Ⅱ的耐热性

NaCl胁迫对杂交酸模幼苗光系统Ⅱ(PS Ⅱ)的最大光化学效率没有影响,但是增强了PS Ⅱ的耐热性.热胁迫条件下,与未经盐胁迫处理的叶片相比,经NaCl 200 mmol/L处理的杂交酸模幼苗叶片,其PS Ⅱ最大光化学效率下降较小,反映OEC受伤程度的指标Fk/Fj上升较小.此外,光化学猝灭系数(qP)、PS Ⅱ反应中心光能捕获效率(Fv1/Fm1)、PS Ⅱ光化学转换效率(ΦPS Ⅱ)的下降以及QB-非还原性反应PS Ⅱ反应中心的相对含量上升程度也较小.探讨了盐胁迫增强杂交酸模幼苗叶片PS Ⅱ耐热性的可能机理.     

4种沙生灌木幼苗PV曲线水分参数对干旱胁迫的响应

以柠条、沙木蓼、杨柴和花棒4种沙生灌木幼苗为材料,采用盆栽法在适宜水分、中度干旱和重度干旱(田间持水量的75%、50%和35%)3种土壤水分条件下,应用PV技术测定了它们在膨压为0时的渗透势(ψstlp)、相对水含量(RWCtlp)和相对渗透水含量(ROWCtlp),以及饱和含水时的渗透势(ψssat)、束缚水含量(Va)、膨压随叶水势下降而降低的速率b值和组织细胞总体弹性模量(ε′)等水分参数,并用隶属函数值法对4种苗木在干旱下保持膨压的能力进行了综合评价.结果显示:与适宜水分条件下相比较,除花棒幼苗在中度及重度干旱下ψssat值、柠条苗在中度干旱下ψssat和ψstlp差值和在中度及重度干旱下Va值、沙木蓼苗在中度干旱下ε′和RWCtlp值均变化很小以外,4种苗木其它水分参数在不同程度干旱胁迫下均有较明显的变化,且其变化幅度随干旱胁迫的加剧而增加,从而使苗木保持膨压及吸水保水的能力较适宜水分下明显增强;苗木保持膨压能力的综合评价结果为:中度干旱下柠条>花棒>杨柴>沙木蓼,重度干旱下柠条>花棒>沙木蓼>杨柴.研究表明,柠条幼苗对干旱胁迫具有极强的渗透调节适应性.     

杉木种子与幼苗不同发育期的耐旱性研究

以广东杉木(Cunninghamia lanceolata)第二代改良种子园种子为试材,利用不同浓度聚乙二醇(PEG-6000)溶液(5%、10%、20%和40%)模拟不同程度(轻度、中度、较强、重度)干旱胁迫,并对不同干旱条件下的种子萌发、幼苗子叶期和真叶期不同发育阶段的形态变化进行测定分析。结果发现,杉木种子萌发初期对水分尤为敏感,耐旱性不强,尤其是随干旱程度的加剧,种子起始萌发时间不断后延且发芽率显著降低。子叶后期的杉木幼苗较子叶前期耐旱,真叶期的杉木幼苗对轻度和中度干旱胁迫具有较强的耐受性。     

干旱胁迫下硫营养对小麦光合色素及MDA含量的影响

选用郑引1号（高水肥型）和陕合6号（抗旱型）2个小麦品种,通过室内盆栽试验比较了干旱及硫胁迫情况下小麦苗期功能叶片中叶绿素（Chla和Chlb）及丙二醛（MDA）含量的变化。采用自然渐进干旱法控制水分,每天称重。结果表明：无论在正常供水还是干旱胁迫时,供硫处理的叶绿素含量始终高于无硫处理,郑引1号的这种优势明显优于陕合6号,硫营养显示出对叶绿素含量的调节能力。干旱胁迫下,供硫处理的小麦叶片MDA含量始终低于无硫处理。两个试验结果均证实了硫营养能通过调节光合色素及MDA的含量增强作物的抗旱能力。     

干旱胁迫下CO2浓度升高对转StAPX番茄植株耐旱能力的影响

在干旱胁迫伴随大气CO2浓度以及升高的CO2浓度（加倍）条件下,以过量表达番茄类囊体膜抗坏血酸过氧化物酶基因（StAPX）的转基因番茄为试材,探明干旱胁迫TCO2浓度升高对转基因及其野生型番茄植株清除活性氧及耐旱能力的影响。结果表明：升高的CO2浓度明显增加了干旱胁迫下植物的光合水平;升高的CO2浓度明显降低了干旱导致的植物体内H2O2．和O2的积累,影响了干旱胁迫下番茄植株的水．水循环系统的活性氧清除酶活性和小分子抗氧化物质含量;干旱胁迫下即使伴随升高的CO2浓度,测试番茄植株体内的渗透调节物质含量变化也不太明显;升高的CO2浓度明显降低了干旱胁迫下的植物细胞膜伤害程度;干旱胁迫下,升高的CO2浓度对转基因番茄株系比对野生型植株的影响更加明显。结果证明干旱逆境下,升高的CO2浓度能够在一定程度上进一步提高转基因番茄植株的耐旱性。