黄瓜幼苗非结构性碳水化合物代谢对干旱胁迫与CO2倍增的响应

以‘津优1号’黄瓜水培幼苗为试材,采用裂区设计,主区设大气CO₂浓度(约380 μmol·mol^-1)和倍增CO₂浓度(760±20 μmol·mol^-1)2个CO₂浓度处理,裂区设无干旱胁迫、中度干旱胁迫和重度干旱胁迫3个水分处理(以PEG 6000模拟根际干旱胁迫),研究了黄瓜幼苗非结构性碳水化合物代谢对干旱胁迫和CO₂倍增的响应.结果表明: CO₂倍增促进了黄瓜叶片中非结构性碳水化合物(葡萄糖、果糖、蔗糖、水苏糖)的积累,降低了渗透势,提高了黄瓜的耐旱性.在干旱胁迫处理过程中,叶片中蔗糖合成酶、可溶性酸性转化酶和碱性转化酶活性先上升后下降;根中可溶性酸性转化酶和碱性转化酶活性则逐渐上升,蔗糖磷酸合成酶活性先上升后下降.CO₂倍增提高了蔗糖合成酶的活性而降低了蔗糖磷酸合成酶的活性,这两种酶和转化酶相互配合,促进了蔗糖的分解和抑制蔗糖合成,导致己糖积累,从而降低了细胞的渗透势,增强吸水能力.因此,CO₂倍增能缓解干旱胁迫造成的不利影响,提高黄瓜的耐旱性,并且这种缓解效应在干旱胁迫严重时表现更为明显.

Dynamic responses of growth and gas exchange parameters of Isatis indigotica seedlings to different concentration amide nitrogen

The effects of doubled CO₂ concentration on non-structural carbohydrate metabolism of cucumber (Cucumis sativus L. cv. ‘Jinyou No.1’) seedlings under drought stress were investigated. Split plot design was deployed, with two levels of CO₂ concentrations (ambient CO₂ concentration, 380 μmol·mol^-1, and doubled CO₂ concentration, 760±20 μmol·mol^-1) in the main plots, and three levels of water treatments (control, moderate drought stress, and severe drought stress) simulated by PEG 6000 in the split plots. The results showed that non structural carbohydrates of cucumber leaves, including glucose, fructose, sucrose, and stachyose, increased with the doubling of CO₂ concentration, which resulted in the decreased osmotic potential, improving the drought stress in cucumber seedlings. During the drought stress, sucrose synthase, soluble acid invertase and alkaline invertase started with an increase, and followed with a decline in the leaves. In the root system, however, soluble acid invertase and alkaline invertase increased gradually throughout the whole process, whereas sucrose phosphate synthase firstly increased and then decreased. The treatment of doubled CO₂ enhanced the activity of sucrose synthase, but decreased the activity of sucrose phosphate synthase. The synergistic action of the two enzymes and invertase accelerated the decomposition of sucrose and inhibited the synthesis of sucrose, leading to the accumulation of hexose, which lowered the cellular osmotic potential and enhanced the water uptake capacity. In conclusion, doubled CO₂ concentration could alleviate the adverse effects of drought stress and improve the drought tolerance of cucumber seedlings. Such mitigating effect on cucumber was more significant under severe drought stress.