喀斯特特有植物罗甸小米核桃幼苗对光照强度的可塑性响应

研究光照强度对1年生喀斯特特有植物罗甸小米核桃幼苗可塑性的影响,探讨其在个体定居初期如何响应不同光照强度的变化及其生态适应策略.设置约为自然光100%、75%、50%和25%的光照强度处理材料,4个月后收获,比较分析罗甸小米核桃幼苗的形态、生物量分配和生理性状在不同光照强度处理下的差异,并对可塑性指标进行综合评价.结果表明,在中度光强(50%自然光照)下,植物采取增加高度,增大叶面积,增加各部位(根茎叶)的生物量分配,提高叶绿素含量、光合作用,促进游离脯氨酸含量积累和超氧化物歧化酶(SOD)活性来综合调控,此时的丙二醛(MDA)积累量最低、为34.77 nmol/g,说明植物在这种光照强度下适应性最强.其次为高光强(75%自然光照)下,植物的以上各功能性状表现也能达到良好状态.此外,在低光强(25%自然光照)下,植物也具有较高的比叶面积、光合参数等性状.综合看植物各可塑性指标(0.06-0.52),生物量分配>生理性状>形态性状,且根冠比与过氧化物酶(POD)活性可塑性指数最大、分别为0.52和0.51,叶片厚度与SOD活性最小、分别为0.08和0.06.综上所述,在个体定居初期,喀斯特特有植物罗甸小米核桃幼苗各形态、生物量分配和生理性状响应光照强度的敏感程度及调控机制存在明显差异,仅在全光下诱导植物出现明显的抑制表型性状外,在高中低光强下均能灵活地塑造其自身性状来协同维持植物正常生长发育,具有的光照幅较广和可塑性强的特点可能是保证其稳定生存在这种喀斯特高度异质性生境的两个重要原因.(图4表3参42)

Plastic response of the karst endemic plant Juglans regia L. f. luodianense seedings to light intensity

This study was conducted to better understand the effect of light intensity on the plasticity of 1-year old Juglans regia L. f. luodianense seedlings, and to assess their response to different light intensities and their ecological adaptation strategies in the early period of individual establishment. After 4 months of treatment under approximately 100%, 75%, 50%, and 25% of natural light, the material harvested was compared to analyze the differences in various morphological characteristics, biomass allocation, and physiological characteristics of seedlings of J. regia L. f. luodianense, and a comprehensive evaluation of the plasticity indices was conducted. The results showed that under moderate light intensity(50% natural light), the plant showed increased height, increased leaf area, increased biomass distribution of each part(root, stem, and leaf), increased chlorophyll content and photosynthesis, promoted free proline content accumulation, and superoxide dismutase(SOD) activity was increased to regulate synthesis. At this time, the minimum accumulation of malondialdehyde(MDA) was 34.77 nmol/g, indicating that the plant is most adaptable under this light intensity. Second, under high light intensity(75% natural light), the above functional traits of the plant can also reach a good level. In addition, under low light intensity(25% natural light), plants also have higher specific leaf area and increased photosynthetic parameters, among other traits. Combining various plasticity indices of plants(0.06-0.52), biomass allocation was as follows: plasticity > physiological traits > morphological traits, and the maximum root-cap ratio and peroxidase(POD) activity plasticity index were 0.52 and 0.51, respectively, while the minimum leaf thickness and SOD activity were 0.08 and 0.06, respectively. In summary, in the early period of individual establishment, there are evident differences in the sensitivity and regulation mechanisms of morphological characteristics, biomass allocation, and physiological indices of the seedlings of J. regia L. f. luodianense in response to light intensity. Only those plants under full light can be induced to show obvious inhibition of phenotypic traits. In contrast, plants under high light, medium, and low light intensity can regulate their own characteristics to maintain their growth and development. The wide light range and strong plasticity of the species might be two important reasons for its existence in a highly heterogeneous karst habitat.