The Effect Of Drought Stress On The Physiology And Biochemistry Of Polygonatum Cyrtonema

Polygonatum cyrtonema is a kind of perennial herbaceous plant.It’s dry underground roots can be used as tonic chinese medicinal materials with excellent value.In addition,it can also be used as shade-tolerant ornamental plants,which has great development and utilization space in the field of ornamental gardening.At present the academic research on P.cyrtonema is mainly focused on the distribution of germplasm resources and the development of medicinal components,but the research on the high-yield and high-quality cultivation technology of P.cyrtonema is relatively few,and artificial is an effective way to solve the shortage of P.cyrtonema resource supply and realize the sustainable development of related industries.In this study,the three-year-old seedlings of P.cyrtonema were used as experimental materials,and four drought stress gradients were set by pot cultivation under canopy and water control:80%soil saturated volume water content(control group,CK),65%soil saturated volume water content(mild drought stress group,T1),50%soil saturated volume water content(moderate drought stress group,T2),35%soil saturated volume water content(severe drought stress group,T3).In order to provide data reference for artificial cultivation of P.cyrtonema,the effects of different drought stress levels on growth morphology,rhizome polysaccharide content,photosynthetic characteristics,osmotic regulatory substances and antioxidant enzymes were studied.The main conclusions of this study are as follows:(1)Drought stress was not conducive to the growth of shoot and the increase of rhizome weight of shoot.With the deepening of soild drought stress,plant height,ground diameter and leaf area of aboveground part of P.cyrtonema decreased,while rhizome width and weight of underground part decreased.Correlation analysis showed that rhizome weight was positively correlated with plant height and ground diameter,and rhizome weight could be predicted by plant height and ground diameter of P.cyrtonema.(2)Mild drought stress could promote the accumulation of polysaccharides in the rhizome of P.cyrtonema.The content of polysaccharide in the rhizome of P.cyrtonema was relatively high under the condition of 65%-80%saturated water content.(3)With the aggravation of drought stress,the chlorophyll(a+b)content of P.cyrtonema showed a general downward trend,and the deeper t he drought stress,the greater the decrease.However,carotenoid content increased with drought stress.(4)Drought stress can inhibit the photosynthesis of P.cyrtonema,and reduces it’s maximum net photo synthetic rate,and P.cyrtonema under moderate drought stress is more prone to the phenomenon of photosynthetic nap.Under mild drought stress,the diurnal variation of net photosynthetic rate of P.cyrtonema shows a single peak curve,while under moderate and severe drought sress,the diurnal variation of net photosynthetic rate shows a double peak curve,and the photosynthetic siesta phenomenon appeared.Regression analysis shows that the net photosynthetic rate of P.cyrtonema under drought stress is mainly affected by stomatal conductance of physiological factors.(5)When under drought stress,P.cyrtonema dissipates excess light energy through chlorophyll fluorescence channel to reduce drought stress damage.When under moderate drought stress,the maximum photosynthetic efficiency of photosystem II,the potential activity of photosystem II and the photo synthetic electron transfer efficiency decreased significantly.(6)When under the influence of drought stress,P.cyrtonema could resist the effects of drought stress through a series of physiological and biochemical regulation processes.With the aggravation and persistence of drought stress,the activities of antioxidant enzymes,the content of malondialdehyde and the content of osmotic regulatory substances including soluble protein and soluble sugar increased.(7)The antioxidant enzyme system of P.cyrtonema can maintain ability to resist drought stress in a period of time.Embodied in the continuous of drought stress,the activity of CAT,POD and SOD is on the rise,to eliminate the influence of superoxide,and then begin to decline after peak point.In conclusion,under the condition of 65%-80%soil saturated water content,the 3 year seedlings of P.cyrtonema show good performance in shoot growth,rhizome weight increase and rhizome polysaccharide content accumulation,and maintain strong resistance to drought stress.