Adaptive responses to drought of two Retama raetam subspecies from Tunisia

两个突尼斯细枝豆属植物亚种对干旱的适应性响应

Aims The survival and ecological distribution of plants in arid habitats are mainly conditioned by water availability and physiological adaptations to withstand drought.In the present study,we have compared the physiological responses to drought of two Retama raetam(retama)subspecies from Tunisia,one of them living under the desert climate(subsp.raetam)and the other one growing on the coast(subsp.bovei).Methods To physiologically characterize the two R.raetam subspecies,and to elucidate their main mechanisms underlying their tolerance to drought stress,parameters related to seed germination,growth,photosynthesis(net photosynthetic rate,intracellular CO_(2) concentration,transpiration rate,stomatal conductance and water-use efficiency)and accumulation of osmolytes(proline,glycine betaine[GB]and soluble sugars)were determined in 4-month-old plants subjected to stress for up to 1 month.Important Findings Drought significantly inhibited germination,growth and all the evaluated photosynthetic parameters.Plants of R.raetam subsp.bovei were severely affected by drought after 3 weeks of treatment when photosynthesis rates were up to 7-fold lower than in the controls.At the same time,proline and GB significantly accumulated compared with the irrigated controls,but much less than in R.raetam subsp.raetam;in the latter subspecies,proline and GB increased to levels 24-and 6-fold higher,respectively,than in the corresponding controls.In summary,the population living in the desert region exhibited stronger tolerance to drought stress than that adapted to the semiarid littoral climate,suggesting that tolerance in R.raetam is dependent on accumulation of osmolytes.

干旱生境植物的生存和生态分布主要取决于水的可获得性以及植物抵御干旱的生理适应能力。在本研究中,我们比较了来自突尼斯的细枝豆属植物Retama raetam的两个亚种对干旱的生理响应,其中一种生长在沙漠气候下(raetam亚种),另一种生长于海岸带(bovei亚种)。为了对这两个亚种进行生理表征并揭示它们耐旱性的主要机制,从受干旱胁迫最长达一个月的四月龄植株中获取了多项参数,涉及植株的萌发、生长、光合作用(净光合速率、细胞内CO_(2)浓度、蒸腾速率、气孔导度和水分利用效率)和渗透物(脯氨酸、甜菜碱和总可溶性糖)积累等。研究结果表明,干旱会显著抑制植株的萌发、生长,对所研究的各项光合参数也都产生很大的负面影响。经过3周的处理后,bovei亚种受到了干旱条件的显著影响,其光合作用速率与对照相比最高下降了7倍。与此同时,该亚种中出现了对脯氨酸和甜菜碱的显著积累(相较于灌溉条件下的对照),但远低于raeMm亚种;在raetam亚种中,脯氨酸和甜菜碱分别增加至相应对照的24和6倍。综上所述,相较于生长在半干旱海岸气候下的细枝豆属植物种群,生长于沙漠地区的种群对干旱胁迫表现出更强的耐性,表明这种耐性在很大程度上取决于渗透物质在体内的累积。