The phytochrome gene family, which is in Arabidopsis thaliana, consists of phytochromes A-E (phyA to phyE), regulates plant responses to ambient light environments. PhyA and phyB have been characterized in detail, but studies on phyC to phyE have reported discrepant functions. In this study, we show that phyD regulates the Arabidopsis gravitropic response by inhibiting negative gravitropism of hypocotyls under red light condition. PhyD had only a limited effect on the gravitropic response of roots in red light condition. PhyD also enhanced phyB-regulated gravitropic responses in hypocotyls. Moreover, the regulation of hypocotyl gravitropic responses by phyD was dependent upon the red light fluence rate.

To analyze the intrinsic relationship between rhizosphere microbial community structure and variety of rice, the microbial community structures in rhizosphere of different hybrid rice cultivars were determined with phospholipid fatty acids (PLFA) analysis. Three series of new-breeding hybrid rice cultivars in China were tested in the experiment, IIyouming 86 (II-32A/Minghui 86), IIyouhang 1 (II-32A/Hang 1), and IIyouhang 2 (II-32A/Hang 2) with II-32A as female parent, XinyouHK02 (XinA/HK02) and YiyouHK02 (YXA/HK02) with HK02 as male parent, Chuanyou 167 (ChuanxiangA/MR167) and 44you167 (Hunan44A/MR167) with MR167 as male parent. The results showed that the microbial community in rhizosphere of the hybrid rice comprised bacteria, fungi, actinomycetes, and protozoa, according to the 40 PLFA biomarkers detected. Bacteria were more abundant than fungi and actinomycetes in rhizosphere of the hybrid rice tested. Both sulfate-reducing and methane-oxidizing bacteria were found to exist in the hybrid rice rhizosphere. It was also found that the characteristics of PLFA biomarkers had correlation with the biological traits of rice. The cluster analysis suggested that microbial community structure and activity in rhizosphere were associated with genetic background of the rice cultivar.