狭叶红景天幼苗对水分及遮阴的生长及生理生化响应

研究植物对水分和遮阴胁迫的响应及其生理机制对制定合理的栽培管理措施十分必要。以红景天属植物为研究对象,设置土壤含水量分别为田间持水量的80%(过湿水分)、70%(正常水分)、60%(轻度干旱)、40%(中度干旱)、20%(重度干旱)5个水分梯度;设置2个遮阴处理,以全光照(遮阴率为0)为对照、黑色遮阴网遮阴(遮阴率为85%),研究狭叶红景天生长及生理生化指标的变化特征。结果表明:在不同水分处理下,与对照相比,叶绿素含量、茎干重和茎重比(SMR)显著增加(P0.05),株高、总生物量、叶面积、叶干重、叶重比(LMR)、比叶面积(SLA)、叶面积比(LAR)和叶面积根干重比(LARMR)增加,根冠比和根重比(RMR)减少;随着干旱程度加剧,丙二醛(MDA)、脯氨酸(Pro)和可溶性糖(Ss)含量增加,超氧化物歧化酶(SOD)活性总体呈先增加后减小的趋势。在遮阴处理下,株高、SMR、SLA、LAR和LARMR显著增加(P0.05),叶绿素SPAD值和叶面积增加,总生物量、根干重、根冠比和LMR显著减少(P0.05),茎干重和叶干重减少,MDA含量显著增加,Pro含量略有下降,Ss含量减少。在水分胁迫下,狭叶红景天中度干旱时通过增加酶活性抵御伤害,重度干旱超过其阈值,SOD活性下降,植物体受到伤害,Ss可能是主要的渗透调节物质。在遮阴处理下,狭叶红景天通过增加SLA避免遮阴伤害。狭叶红景天在受到环境胁迫时会通过形态改变、调节MDA含量、抗氧化酶活性和渗透调节物质来保证自身正常的生长发育。

Growth, physiological, and biochemical responses of Rhodiola kirilowii seedlings to water and shading

It is important to study the responses of plants to water and shading stress and the physiological mechanisms responsible for stress tolerance for rational cultivation management. In the present study, the Chinese medicinal herb, Rhodiola kirilowii, was subjected to five watering and two shading treatments. The watering treatments were applied based on different soil water capacities, i.e., 80% (wet watering), 70% (normal watering), 60% (light drought), 40% (moderate drought), and 20% (severe drought). The shading treatments consisted of full light and shading with 85% black shade netting. Growth, physiological, and biochemical parameters of the treated plants were recorded. Under the different watering treatments, compared with the control, the chlorophyll content, stem dry weight, and stem mass ratio (SMR) increased significantly (P<0.05). In addition, plant height, total biomass, leaf area, leaf dry weight, leaf mass ratio (LMR), specific leaf area (SLA), leaf area ratio (LAR), and leaf area:root mass ratio (LARMR) increased, whereas the root:shoot ratio and root mass ratio (RMR) decreased. With increasing water stress, malondialdehyde, proline, and soluble sugar (Ss) contents increased, and superoxide dismutase activity initially increased but subsequently decreased. Under shading treatments, plant height, SMR, SLA, LAR, and LARMR increased significantly (P<0.05); chlorophyll SPAD values and leaf area increased, whereas total biomass, root dry weight, root:shoot ratio, and LMR decreased significantly (P<0.05), and stem dry weight and leaf dry weight decreased. Malondialdehyde content increased significantly, whereas proline content decreased slightly and Ss content decreased. Under water deficit, R. kirilowii showed increased antioxidant enzyme activity under moderate drought stress, but the threshold was exceeded under severe drought stress, when plants suffered stress-induced injury. Soluble sugars may represent the major osmotic adjustment compounds. Under shading stress, R. kirilowii increased SLA to compensate for decreased incident light. Thus, R. kirilowii altered leaf morphology, MDA content, protective enzyme activity, and osmotic adjustment compounds to ensure normal growth under exposure to environmental stress.