Eco-physiology Responses Of Camellia Oleifera To The Drought Stress

Camellia oleifera is the South China edible oil major woody species.The aim of this study is to explore the eco-physiology responses of Camellia oleifera to the drought stress,and to provide some water management reference in Camellia oleifera production.In this study,7-year-old “Changlin-4” Camellia oleifera forests were used as experimental materials.In order to control the soil moisture to stress Camellia oleifera forests,automatic irrigation equipment for drip irrigation was used.Four different treatmentswere set up,they were severe drought stress(soil moisture content was 15%~20%),moderate drought stress(soil moisture content was 20%~25%),mild drought stress(soil moisture content was 25%~30%)and control(natural condition).Leaf morphological structure,photosynthesis indexes,physiological and biochemical indexes of Camellia oleifera had been studyed under different drought stress.Main research conclusions are as follows:1.Leaf structure responses of Camellia oleifera to the drought stressThe results showed that leaf fresh weight,leaf dry weight,and saturated weight of Camellia oleifera were on the decline with the decreasing of soil moisture,drought stress significantly reduced the leaf thickness and leaf size,the stomatal area,perimeter,aperture,apparatus length and width of leaf lower epidermis also decreased significantly,the stomatal density decreased firstly and then increased.As the drought stress became more intense,the thickness of leaf upper and lower epidermis decreased significantly,the upper and lower cuticle thickness increased significantly,the thickness of palisade tissure,the ratio of the palisade tissue spongy tissue decreased significantly.As drought stress was intensified,the thickness of the main veins of the leaves and the midrib protuberant degree increased significantly,the thickness of xylem and short diameter of vascular bundle under moderate and severe drought stress were significantly lower than control,the different treatments of drought stress had no significant effect on the thickness of phloem.2.Photosynthesis responses of Camellia oleifera leaves to the drought stressAs drought stress was intensified,the net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs)and WUE was on the decline,the intercellular CO2 concentration(Ci)increased,Ci under mild stress was very close to the control;The day average of Pn,Tr and Gs decreased during the drought stress,the double peak trend became single peak gradually.Ci was first increased and then decreased under moderate and severe drought stress,diurnal variation of Ci was "W" curve under mild drought stress and natural condition,these two treatments were in the lowest point at 10 and 14 O'clock,WUE had been at a low level under severe stress,under mild and moderate stress,WUE was slightly decreased under mild and moderate stress.3.Physiological and biochemical responses of Camellia oleifera leaves to the drought stressAs the drought stress became more intense,SOD activity and POD activity of Camellia oleifera leaves were first increased and then decreased,however,the activity of the two enzymes was still higher than that of the control under severe drought stress,the range of POD activity increased was less than SOD;MDA content,soluble sugar content and soluble protein content increased with the drought stress increasing,the changes of these three contents were smaller,however,the changes were significant when subjected to severe stress.4.Endogenous hormones responses of Camellia oleifera roots to the drought stressDrought stress affects the balance of endogenous hormones in plants,With drought stress going on,ABA content of roots increased gradually,IAA content increased under mild and moderate drought stress,then decreased under severe drought stress,the change of GA content was opposite to that of IAA,GA content decreased under mild and moderate drought stress,then increased under severe drought stress,ZR content decreased gradually.