云南松幼苗生物量和非结构性碳水化合物特征的干旱响应

Non-Structural Carbohydrate and Biomass Characteristics of Pinus yunnanensis Seedlings under Continuous Drought Stress

【目的】研究云南松幼苗生长和非结构性碳水化合物(NSC)对持续干旱胁迫的响应,为该物种的种群动态与制定合理经营措施提供理论基础,同时也为干旱条件下人工林营造特别是苗木管护提供依据。【方法】2年生云南松苗进行盆栽试验,采用称重控水法,将土壤相对含水量分别控制在田间持水量的75%~85%(对照)、60%~70%(轻度干旱)、45%~55%(中度干旱)和30%~40%(重度干旱),分析不同干旱处理对幼苗地径、苗高、生物量积累与分配和NSC含量的影响。【结果】1)随土壤干旱程度增加,幼苗地径和苗高增长量、针叶、茎、粗根和整株生物量均逐渐降低;但细根生物量逐渐增加,重度干旱下显著增加22.79%。2)随土壤气候程度增加,幼苗针叶、茎和粗根NSC含量均有不同程度的增加,重度干旱下显著增加10.89%、45.37%、30.70%,细根NSC含量则出现不同程度的降低;各器官可溶性糖与淀粉的比例存在干旱胁迫响应差异,且比值均大于1;淀粉是云南松幼苗最主要的NSC贮藏形式,主要贮藏于茎和粗根。3)干旱胁迫下,云南松幼苗的生物量和NSC器官分配比例变化规律相似,即随土壤干旱程度增加,叶的生物量和NSC分配比例逐渐减小,茎、细根的生物量和NSC分配比例逐渐增加,粗根的生物量和NSC分配比例则先下降后上升。4)幼苗生长与非结构性碳水化合物普遍存在显著相关;可塑性和PCA分析表明,苗高和地径的可塑性指数相对较小,而针叶生物量、细根生物量比、茎淀粉、针叶和茎可溶性糖/淀粉的可塑性指数较高,在主成分上的载荷较大。【结论】干旱胁迫显著抑制云南松幼苗生长。当碳供应受干旱胁迫限制时,存在生长和NSC储存之间的权衡,即生物量和NSC减少对针叶的分配,但增加对细根的分配,是导致云南松幼苗生长缓慢的重要原因。云南松幼苗主要通过调节针叶和细根生长、增加茎贮存淀粉、针叶和茎维持NSC动态平衡来适应干旱环境。

【Objective】This study aims to reveal the changes of Pinus yunnanensis seedling growth and non-structural carbohydrates(NSC)in response to persistent drought stress,in order to provide theoretical support for the population dynamics of this species and the formulation of rational management measures,as well as a basis for plantation establishment,especially seedling management,under drought conditions.【Method】A pot experiment was carried out on 2-year-old P.yunnanensis seedlings,and a weighed water control method was used to control the relative soil water content at 75%–85%(control),60%–70%(mild drought),45%–55%(moderate drought)and 30%–40%(severe drought)of the field water holding capacity to study the effects of different drought treatments on seedling ground diameter,seedling height,biomass accumulation and distribution and NSC content.【Result】1)The seedling ground diameter and seedling height growth,needles,stems,coarse roots and whole plant biomass all gradually decreased with increasing soil drought.However,fine root biomass gradually increased,with a significant increase of 22.79%under severe drought.2)The NSC content of seedling needles,stems and crude roots all increased to different degrees with increasing soil climate,with significant increases of 10.89%,45.37%and 30.70%under severe drought,respectively,while the NSC content of fine roots decreased to different degrees.There was difference in the ratio of soluble sugars to starch in various organs in response to drought stress,and the ratios were all greater than 1.Starch was the most important form of NSC storage in P.yunnanensis seedlings,mainly in stems and thick roots.3)Under drought stress,the biomass and NSC organ allocation ratios of P.yunnanensis seedlings changed in a similar pattern,i.e.the biomass and NSC allocation ratios of leaves gradually decreased with increasing soil drought,those of stems and fine roots gradually increased,and those of coarse roots first decreased and then increased.4)Seedling growth was generally significantly correlated with non-structural carbohydrates.Plasticity and PCA analyses showed that the plasticity indices for seedling height and ground diameter were relatively small,while the plasticity indices for needle biomass,fine root biomass ratio,stem starch,needle and stem soluble sugars/starch were higher and the load on the principal components was greater.【Conclusion】Drought stress significantly inhibits the growth of P.yunnanensis seedlings.When carbon availability is limited by drought stress,there is a trade-off between growth and NSC storage,i.e.biomass and NSC are allocated less to needles but more to fine roots,which is an important cause of slow growth in P.yunnanensis seedlings.P.yunnanensis seedlings adapt to drought conditions mainly by regulating needle and fine root growth,increasing storage of starch in stems,and maintaining a dynamic balance of NSC in needles and stems.