Microbial Development in Soils Under Intensively Managed Bamboo (Phyllostachys praecox) Stands

Phyllostachys praecox C. D. Chu et C. S. Chao, a favored bamboo shoot species, has been widely planted in recent years. Four stands with different historical management practices were selected for this study to understand the evolution of soil microbial ecology by determining the effects of a new mulching and heavy fertilization practice on soil quality using microbiological parameters. Compared with the traditional practice (index 1), microbial biomass carbon (MBC) and soil microbial respiration carbon (MRC) with the new management practice significantly decreased (P ＜ 0.01 and P ＜ 0.05,respectively) with 1-2 years of mulching (index 2) and then for continued mulching significantly increased (P ＜ 0.05). The ratios of MBC/TOC (total organic carbon) and MRC/TOC also significantly diminished (P ＜ 0.05) with mulching. The average well color development (AWCD) and Shannon index decreased with mulching time, and the significant decrease(P ＜ 0.05) in Shannon index occurred from index 2 to index 3. The results from a principal components analysis (PCA)showed that the scores of the first principal component for indexes 1 and 2 were significantly larger (P ＜ 0.05) than soils mulched 3-4 years or 5-6 years. Also, the second principal component scores for index 1 were larger than those for index 2, suggesting that the ability of soil microorganisms to utilize soil carbon was decreasing with longer use of the new management practice and causing a deterioration of soil biological properties.

Assumption of Phyto-Hormone Regulation and Gene Activation of Phyllostachys praecox Flowering

By determination of the change of endogenous hormone Zr,iPA,GA3,IAA and ABA during different flower bud differentiation stages of Phyllostachys praecox,which is identified through both field observation and lab analysis,and with the reference to the previous research achievements on bamboo flowering,the flowering mechanism assumption of Phyto-Hormone Regulation and Gene Activation of Ph.praecox is induced in this article:Bamboo flower bud differentiation can be divided into 3 stages,i.e.flower bud induction,flower bud initiation and flower bud development;Bamboo leaves sense and receive flowering signals from environments to change its hormone level,esp.ratios of iPA/ABA and iPA/GA3;Flowering gene is activated once the ratios of iPA/ABA and iPA/GA3 reach a proper threshold,and it produces DNA and RNA carrying flowering code and transports them to top or side buds nearby,and then protein necessary for flower bud differentiation comes out,as a result of which the flower bud induction is trigged and started,followed by flower bud initiation and development.In the induction stage,ratio of C/N is nearly constant,but increases in the initiation stage.Therefore it clarifies that the rising of C/N ratio does not bring about bamboo flowering initially,and it is a follow-up reactions of process initiation of bamboo flowering.It proves that bamboo rhizome is directly involved in the flower bud differentiation.This assumption can well explain mysterious phenomena of bamboo flowering,and by integrating the current several assumptions,answer the difficult and perplexing questions regarding bamboo flowering which have not been answered by the present assumptions.

A comparison on DNA methylation levels in bamboo at five developmental stages

Bamboo shoots grow quickly through the rapid elongation of intemodes. In order to veri~ whether DNA methylation affects bamboo shoot elongation, we compared DNA methylation levels at five develop- mental stages of bamboo （Phyllostachys praecox）, including young bamboo shoot of 40-cm at length （S1）, bamboo shoot of 2-cm at length （S2）, young leaf （Y1）, leaf （Y2）, and aging leaf （M）, by using amplified fragment length polymorphism （AFLP） based on KpnI/MseI and Acc65I/MseI platforms. The polymorphism ratio of methylated to un- methylated DNA sites in bamboo shoot （$1 and $2） was higher than that in leaf （Y1, Y2 and M）. The polymorphism ratio of methylated to un- methylated DNA sites in $2 was highest （32%）. Our results suggest that DNA methylation changed greatly at bamboo growing stages, especially in stage of rapid elongation of intemodes.