Insight into phytohormonal modulation of defense mechanisms to salt excess in a halophyte and a glycophyte from Asteraceae family

Plant and Soil - The aim of this study was to compare the efficiency of three defense mechanisms (ionic balance, osmotic adjustment and counteracting oxidative stress) under low, moderate and high...     

Modelling of soil salinity and halophyte crop production

In crop modelling the soil, plant and atmosphere system is regarded as a continuum with regard to root water uptake and transpiration. Crop production, often assumed to be linearly related with transpiration, depends on several factors, including water and nutrient availability and salinity. The effect of crop production factors on crop production is frequently incorporated in crop models using empirical reduction functions, which summarize very complex processes. Crop modelling has mainly focused on conventional crops and specific plant types such as halophytes have received limited attention. Crop modelling of halophytes can be approached as a hierarchy of production situations, starting at the situation with most optimal conditions and progressively introducing limiting factors. We analyse crop production situations in terms of water- and salt limited production and in terms of combined stresses. We show that experimental data as such may not be the bottleneck, but that data need to be adequately processed, to provide the basis for a first analysis. Halophytic crops offer a production perspective in saline areas, but in other areas long-term use of low quality irrigation water for halophyte production can result in serious soil quality problems. An overview is given of potential problems concerning the use of (saline) irrigation water, leading to the conclusion that soil quality changes due to poor quality water should be considered in determining the areas selected for halophyte growing.     

Germination strategies of halophyte seeds under salinity

Halophytes are plants of saline habitats that grow under conditions that may vary in extremes of temperatures (freezing to very hot), water availability (drought to water logging) and salinity (mild to almost saturation). Halophytes may also face sudden micro-environmental variations within their habitats. In this review we examine some of the factors that determine the ability of seeds of halophytes to germinate when conditions are optimal for seedling growth and survival.Seed dormancy (innate, induced or acquired) is an important means of initiating growth under appropriate conditions. Saline environments are often wet and so the seeds of halophytes may remain un-germinated over extended periods even after imbibition if the external environment does not favour germination and seedling survival. Many perennial halophytes, however, do not possess elaborate dormancy systems because they propagate largely through ramets and have no ecological compulsions for seed germination.The seeds of halophytes also have the capacity to recover from a salinity shock and start germination once salinity is reduced, which may happen following rain. In some cases, imbibition in a low-salt solution may help in osmo-priming and improve germination. Seed heteromorphism is yet another strategy adopted by some halophytes, whereby seeds of different size and colour are produced that germinate consecutively at suitable intervals. Light-dependent germination may also help if the seed is under a dense canopy or buried in debris; germination only occurs once these restraints are removed thus increasing the chances of seedling survival.     

Effects of a seasonal salinity change on periphyton biomass in a shallow tropical lagoon

In the Ebrié Lagoon (Cǒte d'Ivoire), growth of periphyton on bamboo stuck in the sediment is at the basis of the acadja, a low-cost system developed in order to enhance aquaculture of omnivorous fish like the tilapia Sarotherodon melanotheron. A survey based on hydrological, bacterial and algal data (including phytoplankton and periphyton) was conducted from November 1992 to June 1993 in an experimental structure. Climatic and hydrological seasonality was marked during the study. Succeeding to a rainy season, the oligohaline situation starting in November was characterized by low bacterial and chlorophyll biomass attached to the bamboo (respectively 1 and 18 mg m⁻²). The mesohaline situation observed from January featured a sharp increase in periphyton biomass, with a maximum in April (16 and 177 mg m⁻² for bacterial and algal biomass, respectively). The flood of the Agnéby river, induced in June by the local rains, originated again oligohaline conditions. The biomass decrease observed in May and June resulted from a shift towards low salinity (from 9.8 to 1.8 psu), a decrease in light availability (combined effects of a decreasing solar radiation during the rainy season and an increase of water turbidity due to the flood) and a lower phytoplankton biomass (therefore limiting the secondary epiphytism potentialities). In this shallow tropical environment characterized by high nutrient concentrations (due to local hydrology and organic nature of the substrate), the combination of seasonal variations of climatic (light availability), hydrological (salinity) and biological (abundance or lack of epiphytic algae) seems to control the periphyton biomass growing on bamboo. Therefore, marked seasonality in the production of resource available for the target fish would limit the interest of the acadja as an aquaculture system in brackish ecosystems.     

Halophyte and glycophyte salt tolerance at germination and the establishment of halophyte shrubs in saline environments

Saline sites suffer variations in surface salinity, available soil water, temperature, soil crust strength and other factors which can influence germination and establishment. For establishment to occur the germinating seed must capitalise on a window of opportunity. This window can be widened by placing seeds in a low-salt niche, covering the seeds with a mulch (such as vermiculite), spraying the seed and mulch placement with a coating which may stabilise the favourable situation and raise soil temperature. In this paper it is shown that using seeds collected from plants of Atriplex amnicola which produce many volunteer seedlings in their vicinity can assist establishment from direct seeding. These seeds had the ability to germinate under saltier and cooler conditions than seeds from A. amnicola bushes which did not produce volunteers. Seeds of a halophyte (Atriplex lentiformis) and a non-halophyte (Medicago sativa) are able to imbibe water from a saline substrate in a similar manner. The water enables the seeds of both species to mobilise stored growth materials and produce and elongate radicles. When the seedlings try to erect a hypocotyl and spread their cotyledons, the non-halophyte, in a saline medium, becomes flaccid, distorted and dies. The halophyte seedling shows evidence of high salt tolerance in the form of succulence of cotyledons and trichomes on true leaves even before they are visible and goes on to successfully develop a functioning plant. Nevertheless, germination of halophyte seeds is inhibited or severely reduced at salinity levels above 250 mM NaCl and slowed and reduced progressively up to those levels.     

不同刈割程度对油莎豆非结构性碳水化合物代谢及生物量的影响

为探讨不同留茬高度对油莎豆(Cyperus esculentus)非结构性碳水化合物代谢的影响,进一步明确不同留茬高度与油莎豆地上生物量的关系,并寻求最佳刈割高度,该研究以油莎豆为研究对象,测定6个留茬高度(10、20、30、40、50 cm和未刈割)油莎豆叶片生长生理参数、非结构性碳水化合物含量和地上生物量。结果显示:刈割对于油莎豆光合作用有刺激作用,刈割后油莎豆在第1–14天达到再生生长高峰期。留茬30cm油莎豆叶片可溶性糖含量(第7、21和28天)均高于其他处理,分别为9.22%、10.83%、9.07%,其淀粉含量(第14和21天)均高于其他处理,分别为4.88%和4.11%。留茬40 cm (第21、28天)蔗糖含量均高于其他处理,分别为7.88%和11.38%;其果糖含量(第14和21天)均高于其他处理,分别为5.29%和6.40%。刈割促进了留茬30和40cm油莎豆叶片蔗糖磷酸合成酶和蔗糖合成酶活性的提高。留茬10cm抑制了油莎豆叶片蔗糖含量增加和相关酶活性。合计刈割时和收获时的饲草质量之和,留茬30cm油莎豆干草质量最高,为10 605.11kg·hm^-2     

Diverse responses of halophyte and glycophyte Lepidium species to the salt-mediated amelioration of nickel toxicity and accumulation

Journal of Plant Research - Tolerance mechanisms employed by plants under environmental stresses can protect them against other co-occurring stresses. In this study, the effect of pre-exposure and...     

Effects of ramet clipping and nutrient availability on growth and biomass allocation of yellow nutsedge

A glasshouse experiment was conducted to examine how the interactions of nutrient availability and partial ramet clipping affect growth, reproduction and biomass allocation of Cyperus esculentus, an invasive sedge. The plants sprouting from tubers were grown at low and high nutrient levels, and were subject either to no clipping, one, two or three clippings, with each clipping cutting half of the existing ramets at soil level. Our results show that nutrient availability and clipping frequency tended to independently affect most of growth, reproduction and biomass allocation parameters of Cyperus esculentus examined in the present study. Increased supply of nutrients led to an increase in plant productivity and its associated traits. All of the traits, except for the number of ramets, displayed a decreasing pattern with increasing clipping frequency, indicating that Cyperus esculentus had undercompensatory responses to ramet clipping. It is likely that the patterns of plants response to clipping are species specific, and depend on morphological characters of species. Its susceptibility to ramet clipping can offer opportunities for controlling this invasive species through mechanical methods such as mowing. Clipping had little effects on biomass allocation; however, root weight fraction increased with increasing clipping frequency. While nutrient availability and clipping frequency had no influence on leaf carbon concentration at harvest, both of them increased leaf nitrogen concentration, and hence reduced leaf C/N ratio.     

起始生物量比对3种海洋微藻种间竞争的影响

为深入了解饵料微藻与赤潮微藻间的种间竞争关系,通过微藻共培养的方法,研究了起始生物量比(1:4、1:1和4:1)对3种海洋微藻(塔玛亚历山大藻、蛋白核小球藻和湛江等鞭金藻)两两之间种间竞争的影响,并对其作用机制进行了探讨。结果表明:①3种海洋微藻表现出种间竞争的相互抑制效应;②在与塔玛亚历山大藻(简称A)的种间竞争中,蛋白核小球藻(简称C)和湛江等鞭金藻(简称I)均在竞争中占优势,蛋白核小球藻随自身起始生物量比的提高,其竞争优势越加明显,湛江等鞭金藻在A:I=1:1时竞争优势最为明显;在蛋白核小球藻和湛江等鞭金藻的种间竞争中,当C:I=1:4时,湛江等鞭金藻在竞争中占优势,C:I=1:1时,初期湛江等鞭金藻占竞争优势,随蛋白核小球藻的迅速生长,后期蛋白核小球藻占竞争优势,C:I=4:1时,蛋白核小球藻占绝对竞争优势;③由种间竞争抑制参数比较得出:3种微藻的种间竞争强弱依次为蛋白核小球藻>湛江等鞭金藻>塔玛亚历山大藻。蛋白核小球藻和湛江等鞭金藻在起始比例C:I=1:1时,可共培养利用,在海产经济动物育苗中可对其进行适时采收投喂;两种饵料藻对塔玛亚历山大藻具有明显的抑制作用,可为开发利用饵料藻进行赤潮生物防控提供一定的科学依据。     

Effect of NaCl on the activities of glutamate synthase from a halophyte Suaeda maritima and from a glycophyte Phaseolus vulgaris

The action of NaCl on the activity of root and leaf glutamate synthase is compared in a halophyte, Suaeda maritima var. macrocarpa and in a glycophyte Phaseolus vulgaris. The addition of salt in the nutrient medium lowers the activity of glutamate synthase from Phaseolus without affecting that of Suaeda. This result, attributed to the fact that glutamate synthase is stimulated while glutamate dehydrogenase is partly inhibited in the halophyte grown in presence of high NaCl concentrations, suggests that the GS-GOGAT pathway is the primary route for ammonia assimilation. This pathway is especially active in the leaves. In vitro, NaCl (25–300mM) reduces the activity of glutamate synthase in Phaseolus as well as in Suaeda. Comparison with results obtained in situ suggests that there are differences in intracellular compartmentalization between the two types of plant.     

增温、刈割对高寒草甸植被物种多样性和地下生物量的影响

我国高寒草甸表现出退化现象,严重影响着植被物种多样性和生物量生产。本研究以青藏高原高寒草甸为研究区,采用随机区组设计,设置对照、增温、刈割、增温+刈割交互作用4种试验样地,于植被生长季进行植被物种多样性(Margalef指数、Shannon指数、Simpson指数、Pielou指数)和地下生物量的调查,研究增温、刈割对高寒草甸植被物种多样性和地下生物量的影响。结果表明:(1)高寒草甸植被物种多样性在生长季中期(6、7、8月)显著高于初期(5月)和末期(9月),且显著性从2012年到2013年增强。(2)植被物种多样性对增温(3年)、刈割(2年)的响应并不敏感,在增温、刈割单独作用下略有增加,在增温+刈割交互作用下略有减小。(3)增温、刈割趋于增加地下生物量,促使地下生物量在不同土层的分配比例发生变化;随着时间延长,刈割对土壤浅层(0~30 cm土层)地下生物量的影响逐渐加强,而增温对土壤深层(30~50 cm土层)地下生物量的影响逐渐加强。     

Impact of soil salinity on the microbial structure of halophyte rhizosphere microbiome

The rhizosphere microbiome plays a significant role in the life of plants in promoting plant survival under adverse conditions. However, limited information is available about microbial diversity in saline environments. In the current study, we compared the composition of the rhizosphere microbiomes of the halophytes Urochloa, Kochia, Salsola, and Atriplex living in moderate and high salinity environments (Khewra salt mines; Pakistan) with that of the non-halophyte Triticum. Soil microbiomes analysis using pyrosequencing of 16S rRNA gene indicated that Actinobacteria were dominant in saline soil samples whereas Proteobacteria predominated in non-saline soil samples. Firmicutes, Acidobacteria, Bacteriodetes and Thaumarchaeota were predominant phyla in saline and non-saline soils, whereas Cyanobacteria, Verrucomicrobia, Gemmatimonadetes and the unclassified WPS-2 were less abundant. Sequences from Euryarchaeota, Ignavibacteriae, and Nanohaloarchaeota were identified only from the rhizosphere of halophytes. Dominant halophilic bacteria and archaea identified in this study included Agrococcus, Armatimonadetes gp4, Halalkalicoccus, Haloferula and Halobacterium. Our analysis showed that increases in soil salinity correlated with significant differences in the alpha and beta diversity of the microbial communities across saline and non-saline soil samples. Having a complete inventory of the soil bacteria from different saline environments in Pakistan will help in the discovery of potential inoculants for crops growing on salt-affected land.     

Effects of maternal salinity on salt tolerance during germination of Suaeda aegyptiaca,a facultative halophyte in the Arab Gulf desert

Suaeda aegyptiaca is a facultative halophyte found in saline and non‐saline habitats of the Arab Gulf desert, which produces small‐sized undispersible seeds. The interactive effects of maternal salinity and other environmental conditions, such as salinity, light and temperatures, that are prevailing during seed germination have received little attention for a facultative halophyte. This study tested the effects of maternal salinity on salt tolerance during seed germination of S. aegyptiaca under different light and temperature regimes. Seeds collected from both saline and non‐saline habitats of the United Arab Emirates (UAE) were germinated in 0, 50, 100, 200 and 400 mM NaCl, and incubated at 15/25°C, 20/30°C and 25/35°C in both 12‐h light/12‐h dark regimes and continuous darkness. Generally, seeds of the non‐saline habitat were 56% heavier and attained greater germination at the lower temperatures than seeds of the saline habitat. Seeds of the saline habitat germinated better in saline solutions at higher temperatures and in light. Germination was faster for seeds of the saline habitat than for seeds of non‐saline habitats. Germination recovery after transfer to distilled water was significantly greater for seeds from the non‐saline habitat, compared with seeds from saline habitats. Recovery was greater at lower and/or moderate temperatures, compared with at higher temperatures. Germination was significantly faster during recovery, compared with in the saline solutions. The study indicates that the maternal effect of salinity was confounded with the seed‐size effect and it cannot be conclusively confirmed.     

盐胁迫对盐生植物黄花补血草种子萌发和幼苗生长的影响

盐生植物黄花补血草广泛分布于我国西北地区、东北西部以及华北北部,对改良盐碱土壤具有重要的生态作用。以黄花补血草(Limonium aureum(L.)Hill)为材料,研究分析了不同浓度NaCl胁迫对其种子萌发和幼苗生长产生的抑制效应及作用机制。结果表明:低浓度NaCl(25 mmol/L和50 mmol/L)处理不影响黄花补血草种子萌发和幼苗生长,25 mmol/L NaCl甚至促进了根生长,而高浓度NaCl(100 mmol/L和150 mmol/L)处理明显抑制种子萌发及幼苗生长。利用荧光探针的检测结果表明,NaCl处理的幼苗根中过氧化氢(H2O2)和一氧化氮(NO)含量明显高于对照水平。碘化丙啶(PI)染色结合激光共聚焦显微镜观察及检测相对电导率结果显示,高浓度NaCl处理抑制了幼苗根尖伸长区细胞的伸长生长,增加了细胞膜的通透性,对根细胞造成了明显的伤害。此外,高浓度NaCl处理诱导叶片丙二醛(MDA)含量显著升高。以上结果说明,黄花补血草对低浓度的盐具有一定的耐盐性,但高浓度盐降低了种子的萌发率,使幼苗根中H2O2产生增加,抑制根尖伸长区细胞的伸长生长,对根、叶造成明显氧化损伤,从而抑制黄花补血草幼苗的生长。     

Effects of NaCl salinity on 15N-nitrate fluxes and specific root length in the halophyte Plantago maritima L.

The effect of salinity on nitrate influx, efflux, nitrate net uptake rate and net nitrogen translocation to the shoot was assessed in a ¹⁵N steady state labelling experiment in the halophyte Plantago maritima L. raised for 14 days on solution supplied with 50, 100 and 200 mol m^–3 sodium chloride or without sodium chloride. Additionally, salinity induced changes in root morphology were determined. Specific root length increased upon exposure to elevated sodium chloride concentrations due to variations in biomass allocation and length growth of the tap root. Changes in root morphology, however, had a minor effect on nitrate fluxes when expressed on a root fresh weight basis. The decreased rate of nitrate net uptake in plants grown on elevated levels of sodium chloride was almost entirely due to a decrease in nitrate influx. Expressed as a proportion of influx, nitrate efflux remained unchanged and was even lower at the highest salinity level. At all sodium chloride concentrations applied the initial rate of nitrogen net translocation to the shoot decreased relative to the rate of nitrate net uptake. It is concluded that under steady state conditions the negative effect of sodium chloride on the rate of nitrate net uptake at non growth-limiting salinity levels was due to the interaction between sodium chloride and nitrate transporters in the root plasma membrane and/or processes mediating the translocation of nitrogen compounds, possibly nitrate, to the shoot.     

施肥和刈割对垂穗披碱草（Elymus nutans）、中华羊茅（Festuca sinensis）和羊茅（Festuca ovina）种间竞争力的影响

试验选用青藏高原东部高寒草甸普遍存在的3种禾本科牧草垂穗披碱草(Elymus nutans)、中华羊茅(Festuca sinensis)以及羊茅(Festuca ovina)进行种间竞争的野外研究.通过测定3种牧草生物量的干重,对其进行方差分析并计算了相对产量总和(RYT)以及竞争率(CR).结果如下:对实验物种竞争率(CR)的分析表明垂穗披碱草的竞争力最强,中华羊茅次之,羊茅最差.施肥和刈割处理对于原来的竞争格局没有影响,即在施肥、刈割及其交互作用下3种牧草的竞争等级均是一致的.对试验物种混播的相对产量总和(RYT)的分析表明:在中华羊茅与垂穗披碱草的混播中,两种组成物种利用相同的资源,表现出相互竞争的趋势,这种趋势是非密度依赖的;垂穗披碱草和羊茅混播,在低密度时,羊茅和垂穗披硷草可以共享资源,但是随着密度增加,羊茅和垂穗披碱草表现出竞争相同资源的趋势;在中华羊茅和羊茅的混播中,二者在生长过程中能够共享资源,有相互促进的趋势,表现出共生的关系,且是非密度依赖的.     

Early effects of salt stress on the physiological and oxidative status of Cakile maritima (halophyte) and Arabidopsis thaliana (glycophyte)

Early changes in physiological and oxidative status induced by salt stress were monitored in two Brassicaceae plants differing in their tolerance to salinity, Cakile maritima (halophyte) and Arabidopsis thaliana (glycophyte). Growth response and antioxidant defense of C. maritima under 400 mM NaCl were compared with those of A. thaliana exposed to 100 mM NaCl. Salinity induced early growth reduction that is less pronounced in C. maritima than in A. thaliana. Maximum hydrogen peroxide (H₂O₂) level occurred in the leaves of both species 4 h after the onset of salt treatment. A rapid decline in H₂O₂ concentration was observed thereafter in C. maritima, whereas it remained high in A. thaliana. Correlatively, superoxide dismutase, catalase and peroxidase activities increased at 4 h of treatment in C. maritima and decreased thereafter. However, the activity of these enzymes remained higher in treated plants than that in controls, regardless of the duration of treatment, in A. thaliana. The concentrations of malondialdehyde (MDA) reached maximum values at 24 h of salt stress in both species. Again, MDA levels decreased later in C. maritima, but remained high in A. thaliana. The contents of α‐tocopherol remained constant during salt stress in C. maritima and decreased during the first 24 h of salt stress and then remained low in A. thaliana. The results clearly showed that C. maritima, in contrast to A. thaliana, can rapidly evolve physiological and antioxidant mechanisms to adapt to salt and manage the oxidative stress. This may explain, at least partially, the difference in salt tolerance between halophytes and glycophytes.     

不同水盐条件对三江藨草生长和生物量分配的影响

水、盐条件是盐沼生态系统最重要的环境因子,直接影响着植物的生长和繁殖。以莫莫格湿地优势植物三江藨草（Scirpus nipponicus）为研究对象,探究不同水盐条件及其交互作用对湿地植物三江藨草功能性状和生物量分配格局的影响,以期加深对湿地盐渍化背景下内陆盐沼植物生态适应对策的了解,为指导湿地水盐管理和植被生态恢复提供基础数据。实验采用室内模拟控制水盐条件的方法,设置盐度（300、1000、2000、3000、4000 mg/L和5000 mg/L）和水位（-10,0,20,40,60 cm和80 cm）各6个梯度处理,结果表明,三江藨草株高变化仅受水位处理的影响（P<0.05）,随水位的升高株高呈现先增加后下降的趋势;株数变化仅受盐度处理的影响,并且受水位的限制,适宜盐度能促进浅水域植株分株数增加;水位、盐度和二者的交互作用对三江藨草生物量积累及其分配均产生显著影响,随着水位和盐度的升高,三江藨草球茎、地下、地上和单株总生物量均呈先增加后降低的趋势;生物量分配受水盐交互作用较明显,在1000、2000 mg/L和3000 mg/L盐度处理时,随着水位升高球茎生物量分配和地下生物量分配增加,地上生物量分配减少。综合三江藨草的生长特征和生物量累积,认为其在40-80 cm水位和1000-3000 mg/L盐分处理环境中生长状态较好,适宜的盐分处理可以增加三江藨草对水深的耐受程度。     

Effect of local competition on resprouting of Arbutus unedo after clipping

Abstract. To evaluate the effects of local competition on the growth and size variability of sprouts following disturbance in a natural population of Arbutus unedo in Catalonia, plants were cut at the base and a neighbor removal experiment was performed. Removal of neighbors resulted in an increase in the number and biomass of sprouts at 2 and 7.5 months after clipping. Number and biomass of sprouts was also correlated with initial plant size (stump area). Inter-genet competition appeared to be symmetric, and acted to delay the onset of interference among sprouts within a genet. Size variability of sprouts on an individual was positively correlated with their density on the stump, supporting the hypothesis that competition among ramets (sprouts) within a genet is asymmetric. Reduced inter-genet competition from neighbor removal resulted in an increase in the number and biomass of sprouts growing from a stump. This resulted in an increase in the asymmetry of competition among sprouts, and therefore an increase in the size variability of these sprouts.