松嫩草地全叶马兰种群分株养分的季节运转及衰老过程

Nutrient transportation and aging process of ramets in Aster pekinensis populations on Songnen grassland,China

衰老是植物重要的生活史阶段,植物不同器官养分贮藏力及活动力是判断个体衰老的重要依据。目前对于无性系植物不同龄级分株在衰老过程中贮藏器官的贮藏力与活动力的变化规律尚不清楚。全叶马兰(Aster pekinensis)是根蘖型无性系植物,在东北草原,全叶马兰种群主要由3个龄级的分株组成。该研究分析了全叶马兰种群中3个龄级分株(1a、2a和3a分株)的茎基部、根颈和主根中可溶性碳水化合物(WSC)含量在贮藏器官间、龄级间的差异及季节变化规律。结果表明:在枯黄期,全叶马兰种群3个龄级分株中主根的WSC含量普遍大于根颈,根颈和主根的WSC含量均为1a、2a分株显著高于3a分株,1a分株茎基部的WSC含量显著低于2a和3a分株。在整个生长季内,随着生长进程,全叶马兰种群1a分株根颈始终获得养分的优先分配,其WSC含量呈指数形式的持续积累过程,2a和3a分株根颈及3个龄级分株主根在WSC运转上均为先消耗再积累,其WSC含量均呈二次曲线节律消长。全叶马兰3个龄级分株普遍为主根的贮藏力大于根颈,而根颈的活动力大于主根。幼龄分株养分贮藏力和活动力最强,壮龄分株无衰老迹象,老龄分株明显衰老,其养分贮藏力和活动力均显著下降。该研究为了解WSC含量的时空变化与植物种群个体衰老过程的关系提供了一种定性与定量相结合分析的新思路。

Aims Aging is an important process in the life cycle of plants,and the capacity of different organs to store nutrients and their activities in plants are important in judging individual aging.To date,the changes in these aspects during the aging process of different age-class ramets in clonal plants remain unclear.Methods Aster pekinensis is a typical clonal plant with a root sucker.On the grassland of Northeast China,its ramets are mainly composed of three age classes(1a,2a and 3a).In this study,the differences in water soluble carbohydrates(WSC)contents among storage organs(stem base,root collar,and taproot)or among age classes,and the seasonal variation of rhythm in the three ramets of Aster pekinensis populations were analyzed quantitatively.Important findings At the yellow-leaf stage,the WSC content of the taproot was higher than that of the root collar.The WSC content of root collars and taproots in 1a and 2a ramets was significantly higher than that in 3a ramets.The WSC content of stem bases was significantly lower in 1a ramets than in 2a and 3a ramets.Throughout the entire growth season,the root collars of 1a ramets always received priority allocation of nutrients,and their WSC content continued to accumulate in an exponential form.The nutrient contents in the root collars of the 2a and 3a ramets,as well as the taproots of the three age-class ramets,were all consumed first and then accumulated,and the WSC content changed in the form of a quadratic curve.The capacity of the taproot to store nutrients was generally greater than that of the root collar,whereas the activity of the root collar was greater than that of the taproot across the three age-class ramets in Aster pekinensis populations.The nutrient storage capacity and activity of young ramets were strongest.There were no signs of aging in adolescent ramets.The old ramets were dramatically aged,and their nutrient storage capacity and activity reduced significantly.This study provides a new approach that combines qualitative and quantitative analyses to understand the relationship between the spatiotemporal changes in WSC content and the aging process of individuals in plant populations.