Study On Physiological Response And Adaptability Of Phyllostachys Heteroclada To Water Flooding Stress

Phyllostachys heteroclada is a species of Phyllostachys genus,which belong to Bamboo subfamily,Gramineae family,and widely distributed in Hunan,Zhejiang and other provinces.P.heteroclada grows fast,has strong adaptability,delicious bamboo shoots,and has good bamboo fiber flexibility.It is an excellent bamboo shoot dual-use bamboo species with high economic benefits.Relevant research has also focused on its high-yield cultivation technology.Looking at the suitable area of P.heteroclada,the bamboo species grow well on both sides of the river ditch and even in the long-term flooded depressions,and have high ecological value.However,the adaptation characteristics and response mechanism of P.heteroclada to flooding stress are not clear.By artificially simulating the stress gradient,this paper systematically studied the adaptability and physiological and ecological response characteristics of P.heteroclada under flooding conditions,which has high theoretical and practical significance for revealing the P.heteroclada's resistance to water and humidity and expanding its ecological utilization field.The main results shows as follows:1.Studies on photosynthetic physiological parameters such as photosynthetic stomatal exchange parameters,light response curves,leaf resource utilization efficiency and photosynthetic pigment content under water flooding stress revealed that photosynthetic physiological responses of P.heteroclada leaf under water flooding stress shows the following characteristics.?1?The net photosynthetic rate,transpiration rate and stomatal conductance of the leaves gradually decrease with the increase of stress,and the intercellular CO₂concentration and the deficit of saturated water pressure increase.The secondary stress caused by water flooding cause the signal substances produced by the roots to be transported upward to the leaves,which cause a decrease in stomatal conductance,which affect the photosynthetic rate and transpiration rate.?2?The net photosynthetic rate and maximum net photosynthetic rate of the leaves decrease with the extension of stress time,and the apparent quantum efficiency of the slope of the leaf light response curve vary from 0.032-0.049.The light compensation point of the node stress group increase,and the light saturation point decrease at the same stress time point,indicating that the photosynthetic capacity of the bamboo leaves under water stress decrease.The water use efficiency of bamboo leaves increase with the increase of stress,and the apparent energy use efficiency and apparent CO₂utilization show a downward trend with the increase of stress.The total chlorophyll,carotenoids,chlorophyll a and chlorophyll b of the leaves all decrease with the increase of stress level,the ratio of Chla/Chlb is 1.99-3.37 and the ratio of Chl/Car is 3.79-5.38.2.Studies on the response indexes of H⁺flux of P.heteroclada roots under water flooding stress,changes in antioxidant enzyme activity in leaves and roots,endogenous hormone content,and osmotic adjustment substance content found that the physiological and biochemical response characteristics of leaves and roots in bamboo under water flooding stress are as follows.?1?The first lateral roots of P.heteroclada root are effluxed to H⁺,and the second lateral roots are absorbed.The efflux of H⁺is most obvious when the first lateral roots stress is 24h,and the efflux phenomenon gradually decreases with the extension of the stress time.The efflux absorption of H⁺by the second lateral roots and the first lateral roots is basically the same.The anaerobic respiration of roots under flooding stress exacerbates the H⁺efflux phenomenon,and the self-adjusting stress gradually reduces the H⁺efflux phenomenon as the stress time prolongs,showing that P.heteroclada is extremely resistant to flood stress.?2?The activities of superoxide dismutase,catalase,and peroxidase in leaves and roots of P.heteroclada increase with the degree of stress,and the MDA content under each stress intensity and time node did not reach a significant level?P>0.05?,so the 15-day stress treatment did not cause an imbalance in the removal of active oxygen in P.heteroclada.Abscisic acid content increase,and P.heteroclada increase its resistance by adjusting its own ABA content.The contents of gibberellin and auxin gradually decrease with the increase of stress time.?3?The content of soluble protein in leaves and roots show an upward trend with the extension of stress time.The content of starch and soluble sugar gradually decrease with time.The short-term flooding stress affect the content of osmotic adjustment substances such as nutrients and carbohydrates in the P.heteroclada.3.The nutrient element content and changes of the main vegetative organs such as bamboo roots,branches,stems,and leaves under flooding stress found that the response characteristics of nutrient element of each vegetative organs of P.heteroclada under flooding stress are as below.?1?The C content of plant roots,branches,stems,and leaves showed a downward trend with increasing stress time.Under stress,the absorption of N and P by leaves increase,the N content of bamboo branches increase,the N content of bamboo stems and roots gradually decrease,and the P content of bamboo branches,bamboo stems and roots show a downward trend.The P content is the highest and the bamboo stem is the lowest.?2?Under stress treatment,the C:N ratio of leaves and branches show a downward trend,and the C:N ratio of stems and roots increase.The C:P ratio of the leaves gradually decrease,and the effectiveness of P is negatively correlated with the C:P ratio.The decrease of C:P with the increase of the stress level also indicate that the effectiveness of P element in bamboo leaves under water stress increase.The N:P ratio of leaves is less than 14,its growth is controlled by N elements.The N:P ratio of roots is between 14-16,so its growth is controlled by N and P elements.?3?Under water stress,the absorption of Ca,Fe,and Mg by P.heteroclada leaves and roots increase significantly.The contents of Ca,Fe,and Mg in branches and stems fluctuated within a certain range,and no leaves and roots are significantly affected by the stress.Based on the above research,it has been found that water flooding stress does have certain effects on various physiological and biochemical indicators of P.heteroclada,but P.heteroclada adapts itself to the flooded habitat through enzymes,hormones and other internal adjustments,and the indicators are still in the normal range.Within the value,P.heteroclada in each treatment group was still in good condition at the end of the stress experiment and maintained a normal growth trend.This result provides certain practical guidance significance for using P.heteroclada as a material for ecological environment restoration such as rivers and lakes.