植物的冗余及其生态学意义 Ⅰ.大型水生植物生长冗余研究

Redundancy of plant and it's ecological significance Ⅰ. studies on growth redundancy of aquatic macrophyte

通过水生群落中常见优势种凤眼莲 ( Eichhornia crassipes)根系的去除实验证明了生长冗余的存在 ,并在此基础上对大型水生植物的竞争力、“浮游生物的悖论”及水生群落稳定性的产生与维持作了新的阐述。根系去除实验表明 :群体中凤眼莲植株的根系生长冗余较单株生长时为多 ;这些冗余根系的去除不会对整个植株的生长发育产生明显影响 ;群体中植株根系冗余能够加强植株的竞争能力。生长冗余以及建立在生长冗余基础上的更高层次的冗余结构与生物多样性具有一定的相关性 ,也是生物进化中自然选择的真正对象。据此提出了“进化在生物多样性的基础上进行”

Early in 1983,E.P.Odum pointed out “redundancy can enhance the stability of a ecosystem”,SHENG Chengfa firstly gave a concept of “growth redundancy” in 1991,and demonstrated the over\|compensation in crops.Many scientists carried out researches on the growth redundancy,putting whole interesting in growth redundancy in crops resulting in departure from a state by which men can benefit the most.\;However,this is a subject for which,unfortunately,little evidence has been gathered.Growth redundancy in plants was poorly understood by experiments,there was no direct experiment on proof of growth redundancy in crops or in other plants,and seldom researches came to the issue of growth redundancy in no crop plants.One reason lies in the fact that growth redundancy cannot be investigated directly and great difficulties were encountered in defining “growth redundancy” and its degree.The lack of this work is surprising,and must be addressed.Our comprehension of how growth redundancy emerges,works and evolves will be sadly incomplete without a convincing proof of it and a concerted effort to understand the ecological significance of growth redundancy.\;In this paper,we illustrated root growth redundancy in water hyacinth ( Eichhornia crassipes ),a normally dominant species of aquatic macrophytes with typical fibrous root system,and the growth redundancy degree in plants lived in different habitats.\;We conducted a series of experiments involved different hand\|removal of roots to different Eichhornia crassipes plants lived in 3 different habitats:solely lived,lived in Eichhornia crassipes population and coexisted with Hydrilla verticillata ,a submerged plant easily found in freshwater ecosystems in Yangtze River Basin.In each habitat,3 plants were transplanted and lived for 2 weeks before the experiment.In experiments,the 3 plants in every habitats underwent 3 different hand\|removal of roots respectively,1/3 removed,1/2 removed,and 2/3 removed,to test whether there is a growth redundancy,and,if there is,how about the degree of it.The Eichhornia crassipes plants used for the experiment were selected from the sprouts of the same mother plant with nearly the same leaves and roots to ensure a similar growth potential.\;The plant growth situations,root quantity and root maximum length were investigated one week after the experiments.We found,(i) in solely lived plants,the plant with 1/3 roots removed remained a natural growth,with little new root emerged;the plant with 1/2 roots removed remained a natural growth but many new roots emerged;the plant with 2/3 root removed turned to had a weaken and very slow growth,with little new root;(ii) lived in Eichhornia crassipes population,The plants with 1/3 and 1/2 roots removed both have flowered,and had the same root growth situation to the corresponding experimental plant in the former experiment.But,the one with 2/3 roots removed had only a declined,not weakened,growth with some new roots.It can be said the root growth redundancy in plants lived in population turned out to be much more than that in solely lived plants;(iii) coexisted with Hydrilla verticillata, The plants with 1/3 and 1/2 roots removed both have flowered as in the 2\+\{nd\} experiment.The plant with 1/2 roots removed had many long and new roots,and the one with 2/3 roots removed had a declined growth and some much longer roots.\;Our data provided evidence for that there does exit growth redundancy in root of Eichhornia crassipes. The growth redundancy in root of Eichhornia crassipes plant lived in population or coexisted with Hydrilla verticillata are much more than that of the solely lived plants,and the longer root length in plants coexisted with Hydrilla verticillata was thought to be important for enhancing the competitive ability of Eichhornia crassipes plant.Based on this fact,it is suggested that the growth redundancy is indispensable for improved nutrient uptake in plants and enhanced competitive ability.\;As a fundamental of redundancy,groth redundancy in plant or