Abstract:
A field experiment was conducted in Xishuangbanna during the dry season to study photosynthetic and growth characteristics of 2-year-old
Rauvolfia vomitoria Afzel. under different water and nitrogen treatments. A well-watered condition and a water-stress condition for the water treatments, along with zero N, low N (1.25 g·plant
-1) and high N (3.75 g·plant
-1) treatments were used in the study. The results show that leaf relative water content (
LRWC), maximum net photosynthetic rate (
Pn), stomatal conductance (
gs), specific leaf area (
SLA), stem mass fraction (
SMF) and relative growth rates of height (
RGRH), basal diameter (
RGRD) and biomass (
RGRB) under water-stress condition are lower than those under the well-watered condition. Low N treatment significantly eases water stress induced depression in
Pn, RGRH, RGRD and
RGRB, and increases transpiration rate (
E), root mass fraction (
RMF). This significantly enhances root yield (
YR) compared with zero N and water stress treatment. High N treatment increases drought sensitivity, aggravating photosynthetic and growth depressions of
R. vomitoria. The interaction between N rate and drought significantly affects
LRWC, Pn, instantaneous water use efficiency (
WUEi),
SLA, and
RMF. This implies that different N rates have different effects under different water conditions. It is concluded that low nitrogen fertilization rate during dry season in Xishuangbanna maximizes root yield of
R. vomitoria.