Adaptation of bamboo to heterogeneous habitat: phenotypic plasticity
SHI Jianmin;YE Xuehua;CHEN Fusheng;YANG Qingpei;LI Zuyao;FANG Kai;YANG Guangyao;Forestry College of Jiangxi Agricultural University;Jiangxi Provincial Key Laboratory for Bamboo Germplasm Resources and Utilization;Institute of Botany,Chinese Academy of Sciences;
Since heterogeneity is ubiquitous,plant phenotypic plasticity is a vital ecological countermeasure to adapt to the heterogeneous habitat. Owing to the double modularity,the clonal plant has higher phenotypic plasticity and then acquires higher adaptability than other plants. Bamboo is a group of clonal plants,and mainly composed of woody plants. Bamboo could grow well in the difficult site and heterogeneous habitat where most plants hardly survive. Meanwhile,bamboo can expand rapidly to broad-leaved forest in the bamboo-forest ecotone. Compared with most plants,bamboo has stronger adaptability to heterogenous habitat due to its higher phenotypic plasticity. Thus,in order to advance the development of bamboo ecology, it is necessary to systematically summarize the bamboo phenotypic plasticity and adaptation countermeasures to heterogeneous habitat. Literature analysis shows that bamboo has obvious phenotypic plasticity to respond to heterogeneous habitat. Four realizing ways of phenotypic plasticity including morphological plasticity, selective placement,clonal integration and intraclonal division of labor,are exerted by bamboo to cope with heterogeneous habitat.Firstly,bamboo modifies the morphology,such as height,diameter,leaf area,spacer length,node number,branching angle,biomass etc,to adapt to the changes of above-ground or under-ground resources. The morphological modification is adapted to the resource level. In the poor resource habitat,energy is mainly invested in the constructing of absorbingstructures in order to increase resource absorption. In contrast,most energy is invested in the growth of ramet to increase plant biomass in the rich resource habitat. Secondly,bamboo grows more ramets in the fertile microhabitat than that of in the infertile microhabitat. Thus,bamboo can acquire more survival resources and adapt to the unfavorable habitat. The selective placement is achieved by altering the spacer length,branching angle and branching intensity. Clearly,it is an active behavior to adapt to the heterogeneous habitat. Thirdly,clonal integration behavior helps bamboo ramets in unfertile habitat gain resource from those in fertile habitat. Actually,bamboo shoot growth is a typical process of clonal integration,because the new shoot need obtain the nutrients from mother ramets. However,the direction and intensity of clonal integration could be altered with the variation of resource distribution in the heterogeneous habitat. Fourthly,intraclonal division of labor is another important countermeasure to deal with the heterogeneous habitat. Clonal integration and specialization of ramet are two basic prerequisites for intraclonal division of labor. Although many studies of intraclonal division of labor were developed in herbaceous plants,little is known about that in bamboo. Therefore,we need further confirm whether the intraclonal division of labor is commonly used by bamboo. Overall,the present studies focus on modular morphology and biomass allocation pattern,while little attention is paid on the mechanism of phenotypic plasticity. In the future,the researches on bamboo phenotypic plasticity shall be focused on the following 5 aspects: 1) pattern and mechanism of clonal integration;2) influence of clonal integration on ecosystem stability; 3) mechanism of intraclonal division of labor,and its relationship with environment; 4) hierarchical selection of phenotypic plasticity and the environmental effect; 5) differences of phenotypic plasticity in different types of clonal architecture,and their mechanisms.