Responses Of Photosynthetic Physiological Characteristics And Anatomic Structure Of Poplar Leaves And Bark Chlorenchyma To Drought-recovery And Elevated Temperature

There are many researches about response of leaf photosynthetic(high temperature and drought)under global climate changes,but responses on carbon fixation is different from the leaf and bark chlorenchyma that generally exist in the bark(branches)within the epidermis all year are still unknown.For a future of warm dry climate conditions in the northeast,the poplar leaves and bark chlorenchyma were tested to study two organic growth of poplar leaves and bark chlorenchyma under drought re-water and elevated temperature using pot experiment.Through chlorophyll content,chlorophyll fluorescence parameters,photosynthetic gas exchange,antioxidant enzyme system,photosynthetic enzyme system and anatomical structure were determined the differences of leaves and bark chlorenchyma under climate changes.The experimental results are as follows:(1)The effects of drought-recovery on leaves and bark chlorenchyma were difference.The effects of drought-recovery on chlorophyll fluorescence parameters of leaves were significantly,gas exchange of leaves and bark chlorenchyma have significantly effects:?PSII,qP and ETR of leaves reduced 50%above under drought stress,and the same time two organization Pn decreased by 76%and 81%,R reduced by 22%and 49%,water use efficiency increased by 13%and 13%O2·-of leaves and bark chlorenchyma increased by 32%and 18%under drought stress,H2O2 of leaves had increased.SOD enzymatic activity of bark chlorenchyma increased by 73%under drought stress,SOD,POD and APX enzymatic activity of leaves increased by 77%,25%and 16%and CAT enzymatic activity decreased by 43%.PEPC,NADP-ME,NADP-MDH,PPDK and Rubisco photosynthetic enzymatic activities of leaves were decreased more than 54%by drought stress,but to the bark chlorenchyma has different effects.NADP-ME,PPDK and PEPC enzymatic activity of bark chlorenchyma has decreased,Rubisco and NADP-MDH has increased.Photosynthetic enzymatic activities characteristics of leaves has recovered after rehydration,but the effects of bark chlorenchyma has significantly difference.Spongy tissue cells of leaves decreased under drought stress,proportion of palisade tissue increased and the effects of anatomical structure of bark chlorenchyma was not significantly.There have no effects on the total chlorophyll,chlorophyll a/b,carbon and nitrogen content and PEPC enzyme michaelis constant of Km of leaves and bark chlorenchyma by drought-recovery.(2)The response of bark and leaves to elevated temperature were different.Elevated temperature could significantly affect the chlorophyll fluorescence parameters,and make NPQ,qP,ETR and ?PSII in bark and leaves appear in the trend of first increased then decreased.elevated temperature could make Pn rise in chlorenchyma of bark and leaves.However,the phenomenon mostly resulted in some remarkable characteristics of photosynthetic gas exchange,such as,Gs,Tr and WUE of leaves respectively increased 6-fold,increased 4-fold,decreased 1-fold under 33?.?C13 of chlorenchyma of bark and leaves respectively increased 9%and,then decreased 12%and 10%under 28?.There were differences between elevated temperature and the oxidation characteristics chlorenchyma,photosynthetic enzymatic activities of bark and leaves of poplar.With elevated temperature,POD,GR and APX increased 65%-56%in chlorenchyma of bark;there were no significant changes of activities of CAT and APX in leaves;there were also no significant changes of activities of NADP-MDH of two chlorenchyma,but NADP-ME increased 50%(bark)and 78%(leaves)under 28?,then respectively decreased 7%and 39%under 33?.There were no significant changes of activities of Rubisco and NADP-MDH of chlorenchyma of bark with elevated temperature,but the activities of Rubisco and NADP-MDH of leaves respectively increased 36%and 81%.There was larger diameter of xylem vessel under 28? and 33? than under 23?.In addition,elevated temperature is no effects on chlorophyll content,SOC,N,MDA,PEPC,Km.(3)The difference between bark and leaves index and the statistical inspection of the stress response.Leaves are higher than bark in multiple indicators,including most photosynthetic fluorescent indicator Pn,,ETR,NPQ,Chl.a+b,G,Tr but they were more lower in respiratory rate and photosynthetic enzyme(R,NADP-ME,Rubisco,PPDK,PEPC and NADP-MDH).During drought-rewatering treatment,half of the 24 parameters(Pn,Gs,Tr,ETR,5 photosyntehtic enzymes,SOD,H2O2 and Chl.a/b)showed lower drought response in stem(41.5%,and 63.7%in leaf),but higher recovery sensitivity(52.8%vs 24.9%in leaf).The second group(R,qP,?PSII O2·-production,and MDA)showed 2-fold higher drought response and 3.4-fold higher recovery sensitivity in leaf.,This research has carried on the statistical tests to these differences.