Production of Polyamines Is Enhanced by Endogenous Abscisic Acid in Maize Seedlings Subjected to Salt Stress

It is known that salt stress and exogenously applied abscisic acid （ABA） can enhance the polyamine content in plants and that salt stress itself can lead to an increase in endogenous ABA production. In the present study, the relationships between salt-induced ABA and polyamine accumulation were inves- tigated using ABA-deficient mutant （vp5/vp5） maize （Zea mays L.） seedlings and ABA and polyamine biosynthesis inhibitors. The results show that reduced endogenous ABA levels, as a result of either the mutation or by using a chemical inhibitor （sodium tungstate）, also reduced the accumulation of polyamines in salt-stressed leaves of maize seedlings. The polyamine synthesis inhibitors D-arginine and α- difluoromethylornithine also reduced the polyamine content of the leaves of maize seedling under salt stress. Both ABA and polyamine enhanced the dry weight accumulation of salt-stressed seedlings and also increased the activities of the two dominant tonoplast membrane enzymes, H^＋-ATPase and H^＋-PPase, when plants were under salt stress. The results suggest that salt stress induces an increase in endogenous ABA levels, which then enhances polyamine synthesis. Such responses may increase a plant＇s tolerance to salt.     

Proanthocyanidins Inhibit Seed Germination by Maintaining a High Level of Abscisic Acid in Arabidopsis thaliana

Proanthocyanidins (PAs) are the main products of the flavonoid biosynthetic pathway in seeds, but their biological function during seed germination is still unclear. We observed that seed germination is delayed with the increase of exogenous PA concentration in Arabidopsis. A similar inhibitory effect occurred in peeled Brassica napus seeds, which was observed by measuring radicle elongation. Using abscisic acid (ABA), a biosynthetic and metabolic inhibitor, and gene expression analysis by real-time polymerase chain reaction, we found that the inhibitory effect of PAs on seed germination is due to their promotion of ABA via de novo biogenesis, rather than by any inhibition of its degradation. Consistent with the relationship between PA content and ABA accumulation in seeds, PA-deficient mutants maintain a lower level of ABA compared with wild-types during germination. Our data suggest that PA distribution in the seed coat can act as a doorkeeper to seed germination. PA regulation of seed germination is mediated by the ABA signaling pathway.     

Boron and calcium increasePisum sativum seed germination and seedling development under salt stress

A beneficial effect of B and Ca application on symbiotic interaction between legume and rhizobia under saline conditions has recently been shown, suggesting conventional agricultural practices to increase crop salt tolerance. However, nothing is known about application of both nutrients on early events of legume development under salt stress, prior to the establishment of a symbiotic interaction. Therefore, the effects of different levels of B (from 9.3 to 93μM B) and Ca (from 0.68 to 5.44 mM Ca) on seed germination, root elongation, plant development, and mineral composition of pea (Pisum sativum L. cv. Argona) grown under 0 to 150 mM NaCl, were analysed. Development of plants previously germinated in the presence of salt was more impaired than that of plants put under salt stress once seeds were germinated. A NaCl concentration of 75 mM and 150 mM inhibited pea seed germination and seedling growth. The addition of either extra B or extra Ca to the germination solution prevented the reduction caused by 75 mM NaCl but not that of 150 mM NaCl. However, root elongation and plant development under salt stress (75 mM NaCl) was enhanced only by addition of both B and Ca. When plants were cultivated in the absence of external N, N content in roots and shoots originating from seeds was diminished by salt and enhanced by B and Ca, suggesting a role of these nutrients in remobilisation of seed nutrient stores. Salinity also led to an extremely high concentration of Na⁺ ions, and to a decrease of B and Ca concentrations. This can be overcome by addition of both nutrients, increasing salt tolerance of developing pea plants. The necessity of nutritional studies to increase crop production in saline soils is discussed and proposed.     

Seed Treatment with Auxins Modulates Growth and Ion Partitioning in Salt-stressed Wheat Plants

Experiments were performed to determine whether seed priming with different concentrations （100, 150, and 200 mg/L） of auxins （indoleacetic acid （IAA）, indolebutyric acid （IBA）, or their precursor tryptophane （Trp）） could alter salinity induced perturbances in salicylic acid and ion concentrations and, hence, growth in wheat （Triticum aestivum L.） cultivars, namely M.H.-97 （salt intolerant） and tnqtab-91 （salt tolerant）. Primed and non-primed seeds were sown in Petri dishes in a growth room, as well as in a field treated with 15 dS/m NaCl salinity. All priming agents, except IBA, increased the final germination percentage in both cultivars. The seedlings of either cultivar raised from Trp-treated seeds had greater dry biomass when under salt stress. In field experiments, Trp priming was much more effective in mediating the increase in grain yield, irrespective of the cultivar, under salt stress. The alleviatory effect of Trp was found to be associated with reduced uptake of Na^＋ in the roots and subsequent translocation to the shoots, as well as increased partitioning of Ca^＋ in the roots of salt-stressed wheat plants. Plants of both cultivars raised from Trp-and IAA-treated seeds accumulated free salicylic acid in their leaves when under salt stress. Overall, the Trp priming-induced improvement in germination and the subsequent growth of wheat plants could be related to ion homeostasis when under salt stress. The possible involvement of salicylic acid in the Trp priming-induced better growth under Conditions of salt stress is discussed.     

Seed Treatment with Auxins Modulates Growth and Ion Partitioning in Salt-stressed Wheat Plants

Experiments were performed to determine whether seed priming with different concentrations (100, 150, and 200 mg/L) ofauxins (indoleacetic acid (IAA), indolebutyric acid (IBA), or their precursor tryptophane (Trp)) could alter salinity inducedperturbances in salicylic acid and ion concentrations and, hence, growth in wheat (Triticum aestivum L.) cultivars, namelyM. H.-97 (salt intolerant) and Inqlab-91 (salt tolerant). Primed and non-primed seeds were sown in Petri dishes in a growthroom, as well as in a field treated with 15 dS/m NaCl salinity. All priming agents, except IBA, increased the final germinationpercentage in both cultivars. The seedlings of either cultivar raised from Trp-treated seeds had greater dry biomass whenunder salt stress. In field experiments, Trp priming was much more effective in mediating the increase in grain yield,irrespective of the cultivar, under salt stress. The alleviatory effect of Trp was found to be associated with reduced uptakeof Na~ in the roots and subsequent translocation to the shoots, as well as increased partitioning of Ca~(2 )in the roots ofsalt-stressed wheat plants. Plants of both cultivars raised from Trp-and IAA-treated seeds accumulated free salicylic acidin their leaves when under salt stress. Overall, the Trp priming-induced improvement in germination and the subsequentgrowth of wheat plants could be related to ion homeostasis when under salt stress. The possible involvement of salicylicacid in the Trp priming-induced better growth under conditions of salt stress is discussed.     

Arabinan Metabolism during Seed Development and Germination in Arabidopsis

Arabinans are found in the pectic network of many cell walls, where, along with galactan, they are present as side chains of Rhamnogalacturonan I. Whilst arabinans have been reported to be abundant polymers in the cell walls of seeds from a range of plant species, their proposed role as a storage reserve has not been thoroughly investigated. In the cell walls of Arabidopsis seeds, arabinose accounts for approximately 40% of the monosaccharide composition of non- cellulosic polysaccharides of embryos. Arabinose levels decline to -15% during seedling establishment, indicating that cell wall arabinans may be mobilized during germination. Immunolocalization of arabinan in embryos, seeds, and seedlings reveals that arabinans accumulate in developing and mature embryos, but disappear during germination and seedling establishment. Experiments using 14C-arabinose show that it is readily incorporated and metabolized in growing seedlings, indicating an active catabolic pathway for this sugar. We found that depleting arabinans in seeds using a fungal arabinanase causes delayed seedling growth, lending support to the hypothesis that these polymers may help fuel early seedling growth.     

Effect of salinity on seed germination,growth and ion content in dimorphic seeds of Salicornia europaea L.(Chenopodiaceae)

The halophyte Salicornia europaea L. is a widely distributed salt-tolerant plant species that produces numerous dimorphic seeds. We studied germination and recovery in dimorphic seeds of Central Asian S. europaea under various salinity conditions. We also tested the effects of various salts on Natand Ktaccumulation during plant development from germination to anthesis under greenhouse conditions. We found good germination（close to control） of large seeds under Na Cl between 0.5 and 2%, Na₂SO₄and 2 Na Cl t KCl t Ca Cl between 0.5 and 3%, and 2Na₂SO₄t K₂SO₄t Mg SO4 between 0.5 and 5%. For the small seeds, we found stimulating effects of chloride salts（both pure and mixed） under 0.5e1% concentrations, and sulfate salts under 0.5e3%. Both types of seeds showed high germination recovery potential. Salt tolerance limits of the two seed types during germination and at the later stages of development were very similar（4e5%）. During plant growth the optimal concentrations of mixed chloride and sulfate salts ranged from 0.5 to 2%. The mechanisms of salt tolerance in the two seed types of S. europaea appear to differ, but complement each other, improving overall adaptation of this species to high salinity.     

Starch Mobilization in Ultradried Seed of Maize （Zea mays L.） During Germination

The effects of ultradry storage on the starch mobilization in maize (Zea mays L.) seed after aging were investigated. The results indicated that there were no significant differences in the content of ATP, starch, and soluble sugar, as well as the activity of amylase, between ultradried seeds and seeds stored at -20℃ during germination. These results were consistent with the higher level of vigor of the ultradried seed. Sieve tube introduction of a fluorescence dye (carboxyl fluoresceindiacetate) and laser confocal microscopy were used to study the development of plasmodesmata in the ultradried seeds. The results indicated that plasmodesmata developed well in ultradried seeds. Fluorescence analysis also showed that the fluorescence intensity in the radicle of ultradried seeds was stronger than that in seeds with a higher moisture content. This suggests that ultradry treatment has no adverse effects on the seeds. After seed imbibition, cell orgaelles could be resumed. It is concluded that ultradry seed storage is beneficial for maintaining seed vigor and that starchy mobilization proceeds regularly during germination.     

Effects of the supply levels and ratios of nitrogen and phosphorus on seed traits of Chenopodium glaucum北大核心CSCD

Aims Global nitrogen (N) deposition not only alters soil N and phosphorus (P) availability, but also changes their ratio. The levels and ratios of N and P supply and their interaction may simultaneously influence plant seed traits. However, so far there has been no experiments to distinguish these complex impacts on plant seed traits in the field. Methods A pot experiment with a factorial design of three levels and ratios of N and P supply was conducted in the Nei Mongol grassland to explore the effects of levels and ratios of N and P supply and their interaction on seed traits of Chenopodium glaucum. Important findings We found that the relative contribution (15%–24%) of N and P supply levels in affecting the N concentrations, P concentrations and germination rates of seeds was larger than that (3%–7%) of N:P supply ratios, whereas seed size was only significantly influenced by N:P. Simultaneously, seed N and P concentrations were impacted by the interaction of N and P supply levels and ratios. At the same N:P, decrease in nutrient supply levels increased seed N concentrations, P concentrations and germination rates. N:P supply ratios only had a significant effect on seed size and germination rates under low nutrient levels. Overall, these results indicate that different seed traits of C. glaucum show different sensitivities to N or P limitations, leading to adaptive and passive responses under different nutrient limitations. This study presents the the first field experiment to distinguish the effects of nutrient supply levels, ratios and their interactions on plant seed traits, which provides a new case study on the influences of global N deposition on future dynamics of plant population and community. © Chinese Journal of Plant Ecology.     

Promotion by 5-Aminolevulinic Acid of Germination of Pakchoi (Brassica campestris ssp. chinensis var. communis Tsen et Lee) Seeds Under Salt Stress

The seed germination and seedling growth of pakchoi (Brassica campestris ssp. chinensis var.communis Tsen et Lee cv. Hanxiao) were not significantly inhibited until the concentration of NaCl was increased to150 mmol/L. Treatment of pakchoi seeds with exogenous 5-aminolevulinic acid (ALA), at concentrations ranging from 0.01 to 10.00 mg/L, promoted seed germination when seeds were stressed by salinity, whereas levulinic acid (LA), an inhibitor of ALA dehydrase, significantly inhibited seed germination and seedling growth, suggesting that metabolism of ALA into porphyrin compounds was necessary for seed germination and seedling growth. Determination of respiratory rate during seed germination showed that ALA increased seed respiration under both normal conditions and salt stress. Furthermore, salt stress decreased levels of endogenous ALA, as well as heme, in etiolated seedlings. More salt-tolerant cultivars of pakchoi contained higher relative levels of endogenous ALA and heme under conditions of salt stress.These results indicate that salt stress may inhibit the biosynthesis of endogenous ALA and then heme,which is necessary for seed germination, and treatment of seeds with exogenous ALA prior to germination may be associated with the biosynthesis of heme.     

外源5-氨基乙酰丙酸对盐胁迫下菘蓝种子萌发及幼苗抗氧化酶活性的影响

采用砂培方式,研究了外源5-氨基乙酰丙酸(ALA)对盐胁迫下菘蓝种子的萌发、幼苗叶片的可溶性糖含量、丙二醛(MDA)含量及其抗氧化酶活性的影响,探讨ALA缓解菘蓝受盐胁迫伤害的响应机制。结果显示:(1)菘蓝种子萌发及幼苗生长在100 mmol·L^-1 NaCl胁迫下受到明显的抑制,种子发芽率、发芽势、发芽指数、活力指数与自然含水量均显著降低,丙二醛含量、可溶性糖含量以及超氧化物歧化酶(SOD)、过氧化物酶(POD)活性显著升高。(2)盐胁迫下适宜浓度的ALA处理显著提高了种子萌发率、自然含水量及SOD、POD和CAT活性,降低了可溶性糖和丙二醛的含量,并以16.7 mg·L^-1 ALA处理盐胁迫下菘蓝种子的发芽率、发芽势最大,其幼苗的SOD、POD、CAT活性最强。研究表明,盐胁迫显著抑制菘蓝种子的萌发及幼苗生长,适宜浓度的ALA能够有效缓解盐胁迫对菘蓝种子萌发及幼苗生长的伤害,提高植株的抗盐性,并以16.7 mg·L^-1 ALA处理效果最佳。     

外源水杨酸对盐胁迫下大黄种子萌发及幼苗生长的影响

该研究以掌叶大黄、唐古特大黄和药用大黄种子为材料,采用双层滤纸培养法,设置系列浓度NaCl (0、100、150、200、250 mmol/L) 胁迫试验,以及系列浓度水杨酸(SA)溶液(0、50、100、150、200、250 mg/L)拌种和浸种后盐胁迫实验,测定3种大黄种子萌发及幼苗生长指标,揭示外源水杨酸对盐胁迫下大黄种子萌发及幼苗生长的影响。结果显示：(1)随NaCl浓度增大3种大黄种子的发芽率均呈直线下降趋势,且子叶、胚轴、根和苗等生长均受到强烈抑制。(2)在拌种条件下, 200 mmol/L NaCl胁迫下掌叶大黄苗长在200 mg/L SA处理下受到显著促进; 200 mmol/L NaCl浓度盐胁迫下唐古特大黄种子发芽率在250 mg/L SA处理下受到显著抑制;100 mmol/L NaCl胁迫下药用大黄种子发芽势在200 mg/L SA处理下受到显著抑制,其发芽率在150 mg/L SA处理下得到显著抑制,其苗长在250 mg/L SA处理下受到显著抑制。(3)在浸种条件下, 200 mmol/L NaCl胁迫下掌叶大黄种子发芽率在50 mg/L SA处理下显著提高,其幼苗根长和苗长的生长在250 mg/L SA处理受到显著促进;200 mmol/L NaCl胁迫下唐古特大黄种子的发芽势在200 mg/L SA处理下得到显著促进,其幼苗根和苗的生长在50 mg/L SA处理下得到显著促进;100 mmol/L NaCl 胁迫下药用大黄根和苗的生长在100 mg/L SA处理下均得到显著促进。研究表明,3种大黄种子和幼苗对盐胁迫的响应趋势一致,但对不同浓度SA拌种和浸种的响应有较大差异。     

外源水杨酸对NaCl胁迫下大豆种子萌发和幼苗生长生理的影响

以大豆种子、幼苗为试验材料,采用砂培的方法,研究了0.2mmol·L-1外源水杨酸(SA)对100mmol·L-1 NaCl胁迫下大豆种子萌发、幼苗形态及生物量、膜脂过氧化和抗氧化酶活性的影响。结果显示:NaCl胁迫下,大豆种子萌发和幼苗生长受到显著抑制,且随着胁迫时间的延长(0~3d),大豆幼苗相对电解质渗漏率、硫代巴比妥酸活性产物(TBARS)含量显著升高,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)活性均明显降低。外源SA促进NaCl胁迫下大豆种子萌发和根茎生长,增加幼苗生物量积累,降低幼苗叶片相对电解质渗漏率和TBARS含量,增强其叶片SOD、CAT、APX活性。研究表明,NaCl胁迫能显著抑制大豆种子萌发和幼苗生长,而一定浓度的外源SA能有效提高NaCl胁迫下大豆种子活力及幼苗抗氧化酶活性,减轻膜脂过氧化程度,缓解NaCl胁迫所造成的伤害,提高大豆幼苗抗盐胁迫的能力。     

外源ALA、SNP和Spd对NaCl胁迫下桔梗种子萌发特性的影响

以药用植物桔梗为研究对象,通过测定不同浓度的ALA、SNP和Spd对NaCl胁迫下桔梗种子发芽势、发芽率、萌发指数和平均根长等萌发指标的影响,寻找提高桔梗种子及幼苗在盐胁迫条件下抗性能力的途径.实验结果表明,75 mmol·L-1 NaCl胁迫下的桔梗种子萌发受到显著抑制,但是用不同浓度的ALA、SNP和Spd对桔梗种...     

水杨酸调控盐胁迫下羽衣甘蓝种子萌发的机理

盐胁迫是植物种子萌发与植株生长的重要限制因子。以羽衣甘蓝(Brassica oleracea var.acephala)名古屋为材料,研究不同盐分对其种子萌发的影响,探索水杨酸(SA)及其合成抑制剂氨基茚磷酸(AIP)处理对羽衣甘蓝种子萌发的调控效应。实验结果表明,150与200 mmol·L^–1 NaCl处理后的羽衣甘蓝种子活力显著降低。盐胁迫显著降低种子的吸水速率、种子活力与幼苗质量,降低苯丙氨酸裂解酶活性与内源SA含量,提高过氧化氢(H2O2)与超氧阴离子(O2^–.)含量。SA可以缓解盐胁迫对羽衣甘蓝种子活力的抑制作用,通过促进内源SA合成,从而提高种子吸水率与种子活力,促进种子对K^+、Mg^2+的吸收,降低Na+含量。此外,外源施加SA能够显著增强超氧化物歧化酶和过氧化物酶活性,降低H2O2与O2^–.的积累。相反,氨基茚磷酸(AIP)处理能够增强盐胁迫对种子萌发的抑制作用,推测这与AIP处理能够显著降低种子内源SA含量密切相关。研究表明外源SA主要通过提高保护酶活性、降低活性氧积累和维持体内离子平衡来增强羽衣甘蓝的耐盐性。     

外源赤霉素GA3对混合盐碱胁迫下小白菜种子萌发的影响

以小白菜（Brassica campestris ssp．chinensis L．）为材料,通过采用不同浓度的外源赤霉素（GA3）浸种处理,研究了GA3对混合盐碱胁迫下小白菜种子的发芽率（Gr）、发芽势（Gv）、发芽指数（Gi）以及根毛区宽度和胚长的影响。结果表明：混合盐碱胁迫下,小白菜各发芽指标均显著低于对照,GA,处理后,各指标均显著提高,且随外源GA3浓度的增加,各指标均表现出先增后减的趋势,当GA3浓度达80mg／L时,各发芽指标达到峰值,说明80mg／LGA3可使混合盐胁迫下小白菜种子萌发的缓解作用达到最佳。同时外源GA3处理还可不同程度地缓解盐胁迫对小白菜种子a-淀粉酶活性的抑制。     

Effects of seed priming with ascorbic acid to mitigate salinity stress on three wheat (Triticum aestivum L.) cultivars.

In this study, the effect of seed priming using ascorbic acid (ASA) on three commercial wheat cultivars i.e., Punjab-2011, Faisalabad-2008, and Ujala-2016 under salinity stress in both homogenous and heterogeneous environments has been investigated. It revealed that different levels of salinity have significantly reduced the growth attributes like percent germination, germination index, radical & plumule length, seed vigor index (In-vitro), seedling length, fresh & dry weight, and total chlorophyll content (In-vivo) with subsequent treatments. Salinity stress was induced by using NaCl in three different concentrations (100, 150, and 200 mM). Seeds of the three cultivars primed with 50, 100, and 150 mg/L ascorbic-acids have not only improved percent germination but also considerably reduced germination time and increased germination index (GI) indicating the potential for tolerating saline conditions. Seedling growth (seedling length, Fresh weight, and dry weight) of seeds primed with 50, 100, and 150 mg/L (ASA) was significantly higher than other non-primed seeds under the prevailing saline conditions. Hormonal priming with different concentrations of ascorbic acid was effective, nevertheless, the best results were obtained with 100 and 150 mg/L (ASA) concentrations. We concluded that the delay in germination and seedling growth was mainly due to excessive Na⁺ accumulation in the seeds of wheat cultivars. On the other hand, seed priming with various concentrations of ascorbic acid has proved to be effective in inducing salt tolerance in terms of germination parameters, seedling characteristics, and chlorophyll retention in the three local commercial wheat cultivars.     

外源H2O2对盐胁迫下小白菜种子萌发和幼苗生理特性的影响

以小白菜"甜脆青"为试材,研究不同浓度（5、10、25、50和100 mmol/L）过氧化氢（H₂O₂）浸种处理对100 mmol/L NaCl胁迫下小白菜（Brassica chinensis L.）种子萌发、幼苗生长及生理特性的影响。结果表明：100 mmol/L NaCl胁迫明显抑制小白菜种子的萌发状况和幼苗生长,发芽势、发芽指数、活力指数及幼苗根和芽长度和鲜重均明显降低,根和芽中CAT的活性及K⁺含量明显受到抑制,渗透调节物质、活性氧和MDA含量显著增加。不同浓度H₂O₂浸种处理提高了NaCl胁迫下小白菜种子发芽势、发芽指数和活力指数,促进小白菜根和芽的生长,增强了NaCl胁迫下根和芽中SOD、CAT和APX的活性及K⁺含量,降低O₂^-·产生速率及H₂O₂和MDA含量,进一步促进脯氨酸和可溶性糖含量的增加,降低体内Na⁺含量。其中以10 mmol/L H₂O₂处理缓解盐胁迫效果最好,明显缓解NaCl胁迫对小白菜种子萌发和幼苗生长的抑制。     

水杨酸和阿斯匹林对小麦盐害的缓解作用

盐胁迫条件下水杨酸和阿斯匹林能提高小麦种子发芽率、发芽指数和活力指数,降低幼苗叶片质膜透性和盐胁迫对细胞膜的伤害,提高幼苗体内超氧化物歧化酶、过氧化物酶等细胞保护酶的活性,减少膜脂过氧化作用产物丙二醛的积累,降低根系Ｎａ＋和提高根系Ｋ＋ 的向上运输选择性。所有这些变化都有利于缓解盐胁迫对小麦的伤害,提高其对盐胁迫的适应性。