Study On Photosynthetic Characteristics Of Amorphophallus Xiei In Different Cultivation Model

Amorphophallus xiei is a typical shade-requiring plant with the advantages of high yield,good adaptability and high content of glucomannan,which is one of the main varieties in Yunnan.The intercropping mode has been widely promoted and applied in agricultural production,and the main concerns of the mode were crop yield,economic benefit,interspecific relationship and control of crop diseases and insect pests.However,less attention was paid to photosynthetic adaptability of crops to dynamic light sources under intercropping mode.In this study,three cultivars were designed,respectively single cropping of Amorphophallus xiei,intercropping with maize and intercropping rubber plantations under different light transmittances.The main contents of this study were as follows:1)Photosynthetic characteristics,characteristics responsed to light spot and intrinsic biochemical changes（such as changes in photosynthetic pigments content and composition,changes in the distribution of nitrogen between photosynthetic and non-photosynthetic organs and different components of photosynthetic apparatus）under different light transmittances were investigated.2)The basic characteristics of photosynthesis,characteristics responsed to light spot and photosynthetic pigments content in the photosynthesis under the intercropping mode were studied;3)The basic characteristics of photosynthesis and haracteristics responsed to light spot were discussed with the change of light environment.This invention project would provide scientific basis for improving the photosynthesis capacity and light utilization efficiency of crops in the process of intercropping cultivation or factory planting,and enrich the basic theory of A.Xiei adapt to dynamic light environment.1.Area-and mass-based maximum net photosynthetic assimilation rate(A_max),photosynthetic pigment content,maximum carboxylation rate,and maximum electron transport rate as well as specific leaf area significantly increased with decreasing growth irradiance levels;however,dark respiration rate and light compensation point decreased significantly.In the process of photosynthetic induction,the induction time to reach 50%of A_max was the shortest（81.4 s）and the induction state of 10 min was the highest（87.3%）in the individuals grown under the 17%of full sunlight.Moreover,there was a negative correlation between the induction time to reach 50%and 90%of A_max and the initial stomatal conductance across all the treatments.The fraction of leaf N allocated to carboxylation and bioenergetics firstly increased and then decreased with the decreasing growth irradiance levels,and the maximum values were recorded in individuals grown under 17%of full sunlight;at the same time,the fraction of leaf N allocated to light-harvesting components increased significantly with decreasing growth irradiance levels.2.The net photosynthetic rate(A_net)of A.xiei under intercropping was 18.97%higher than that under monoculture and the maximum stomatal conductance(g_s-max)was 22.4%lower than that under monoculture.There were high apparent quantum yield（AQY）,light saturation point（LSP）,carboxylation efficiency（CE）and chlorophyll content as well as lower dark respiration rate（R_d）,light compensation point（LCP）and CO₂ compensation point（Г）in A.xiei under intercropping.After inducted by high illumination,the photosynthetic induction state（IS）under intercropping was higher than that under monoculture.During photosynthetic induction,the time required to reach 30%and 50%of A_max were short under intercropping.There were negative relation between initial stomatal conductance(g_s-initial)and the time required to reach 30%,50%and 90%of A_max and g_s-max.3.Dark respiration rate（P<0.05）,light compensation point（P<0.01）and light saturation point（P=0.459）significantly decreased under 5a rubber plantation.Meanwhile,in the process of photosynthetic induction,the time to reach 30%,50%and 90%maximum A_max were shorter and induction state of 1 min,5 min,10 min were higher under the 3a rubber plantation.In general,as a typical shade plant,A.xiei in order to adapt to light scattering and light spot.To decreased the respiration consumption,to broaden scope of light use,which captures more low light energy and maintains the harvest of carbon;The capacity of facula utilization increased by rapiding photosynthetic induction,promoting photosynthetic enzyme affinity to CO₂ and breaking the restriction of photosynthesis of stomata in order to improve the photosynthetic carbon assimilation.