摘要
尽管已有大量的研究考察了非生物胁迫因素对植物的影响,但是我们对干旱造成植物死亡的机理尚无定论,而对多种胁迫因子之间的相互作用更是知之甚少。非结构性碳水化合物(NSCs)在防止或延缓因干旱造成死亡方面的作用正日益引人关注。在本研究中,我们探讨了NSCs在缓解新西兰红树林(Avicennia marina subsp.australasica)受干旱和盐度影响时所起的作用。首先,我们对植物体内的NSC水平进行了实验调控,随后将植株置于不同的干旱和盐度组合环境中培育。研究结果表明,在高盐度且高度干旱的条件下,高NSC水平组(H-NSC)的植物生长速率和存活率分别比低NSC水平组(L-NSC)的高出2和3倍。在高盐度且高度干旱的条件下培育了12周后,H-NSC组植株的茎杆导水率(281±50 mmol cm^(−1)s^(−1)MPa^(−1))高于L-NSC组植株(134±40 mmol cm^(−1)s^(−1)MPa^(−1))。尽管淀粉含量保持相对稳定,但H-NSC组植株茎杆中的可溶性糖含量在高盐度且高度干旱条件下的第8周时比第12周时高出20%。这些研究结果表明:1)NSCs对于缓解因干旱和与之相关的高盐度造成的较低土壤水势的影响具有重要作用;2)旱、盐联合胁迫下的植株生长受到库的限制。
Despite a large number of studies examining the effects of abiotic stress factors on plants,the mechanistic explanations of drought-induced tree mortality remain inconclusive and even less is known about how multiple stressors interact.The role of non-structural carbohydrates(NSCs)in preventing or postponing drought mortality is gaining attention.Here,we tested the role of NSCs in mitigating the effects of drought and salinity in New Zealand mangroves,Avicennia marina subsp.australasica.We experimentally manipulated plant NSC levels,prior to subjecting them to combinations of drought and salinity.Plant growth and survival rates were 2-and 3-fold higher in the high-NSC(H-NSC)group than in the low-NSC(L-NSC)group under high salinity and drought conditions,respectively.After 12 weeks under high salinity-high drought conditions,the H-NSC group showed higher stem hydraulic conductivity(281±50 mmol cm^(−1)s^(−1)MPa^(−1))compared with the L-NSC group(134±40 mmol cm^(−1)s^(−1)MPa^(−1)).Although starch levels remained relatively constant,we found a 20%increase in soluble sugars in the stems of H-NSC group under high drought and high salinity in week 8 compared with week 12.Our results suggest(i)an important role of NSCs in mitigating the effects of low soil water potential caused by drought and salinity,and(ii)sink-limited growth under conditions of combined salinity and drought.
