Physiological Response Of Parthenocissus Quinquefolia And Cornus Stolonifera Seedlings To Saline And Alkali Stress

The changes in growth,photosynthesis,osmorequlatory,the production and elimination of reactive oxygen species(ROS) in leaves of 1-year-old Parthenocissus quinquefolia and Cornus stolonifera plants were tested systematically under different NaHCO₃ stresses(0.0,1.0,2.0 and 4.0 g·kg^-1 dry soil,viz.,control,low salt stress,moderate salt stress and high salt stress) and different phases(10 d,20 d and 30 d),taken by the method of plant-plotted.The objective of this study was to reveal the changes of growth and physiological biochemical of Parthenoc-issus quinquefolia and Cornus stolonifera seedlings and to estimate the tolerance scopes of the two plants.The main results were as follows:(1) With the increasing stress intensity,the growths of Parthenocissus quinquefolia and Cornus stolonifera were prohibited.Low NaHCO₃ stress indistinctively prohibited the growths, while which were significantly limited under moderate and high stresses in the two plants.The effects of salt stress on growth of Parthenocissus quinquefolia were stronger than that of Cornus stolonifera.Compared with control,the height relative growth increment were respectively 11.2%(low salt stress),37.2%(moderate salt stress) and 58.1%(high salt stress) in Parthenocissus quinquefolia(P＜0.05),however,20.5%(low salt stress),32.9%(moderate salt stress) and 54.0%(high salt stress),respectively,in Cornus stolonifera(P＜0.05).The relative dry weight of different organs and whole plant were decreased with salt stresses.The relative dry weight of whole plant decreased insignificantly under low salt stress, but decreased significantly under moderate and high salt stress in the two plants.The relative dry weight decreasing scales was less in Parthenocissus quinquefolia(41.3%and 59.9%under moderate and high salt stresses)(P＜0.05) than that Cornus stolonifera(22.6%and 53.9% under moderate and high salt stresses)(P＜0.05).(2) The photosynthesis was suppressed significantly in Parthenocissus quinquefolia and Cornus stolonifera plants under salt stresses,and the main changes were total chlorophyll content and net photosynthetic rate(Pn) in leaves of the two plans were decreased.The decreasing scales of net photosynthetic rate(Pn) were less in Parthenocissus quinquefolia (24.5%and 41.8%under moderate and high salt stress)(P＜0.05) than that Cornus stolonifera (26.1%and 78.4%under moderate and high salt stress)(P＜0.05).The photosynthetic rate in leaves of Parthenocissus quinquefolia was result from stomata limitation at low stress and non-stomata restriction gradually became the main limit factor with stress enhanced,while that non-stomata restriction was the major limit factor that leading to decreasing in photosynthetic rate of Cornus stolonifera.(3) Parthenocissus quinquefolia and Cornus stolonifera could enhance the salt tolerance by accumulating the Na⁺ content in root under low and moderate salt stresses.The organic osmotica content,such as proline,soluble sugar and soluble protein increased and played a part in osmoregulation.At long-time stress stage,compared to corresponding control,the content of proline under low,moderate and high salt stress was increased by 128.8%,214.5%and 303.2% (P＜0.01),while soluble protein content was increased by 24.3%,42.8%and 54.1%,soluble sugars content increased by 53.8%and 76.7%in Parthenocissus quinquefolia.Proline content in Cornus stolonifera was higher 71.3%(low salt stress),80.9%(moderate salt stress) and 145.4%(high salt stress) than control(P＜0.01).(4) The plasmalemma wholeness of the two plants was maintained well under low salt stress.Plasmalemma permeability increased with salt stresses strengthened.Malondialdehyde (MDA) content in leaves of Parthenocissus quinquefolia and Comus stolonifera seedlings were insignificantly accumulated under low salt stress,however,they were obviously accumulated and the plasmalemma wholeness were breaked under moderate and high salt stress.At long-time stress stage,MDA content and membrane permeability of Parthenocissus quinquefolia were 1.4 and 3.5(P＜0.01) times of that in control,while 4.7 and 2.8(P＜0.01) times of that in control of Cornus stolonifera.(5) Under specific salt stress,the two plants could eliminate reactive oxygen species(ROS) through the changes in antioxidant system.For Parthenocissus quinquefolia,APX activity(10 d) was higher 40%(low salt stress) and 37%(moderate salt stress)(P＜0.05) than control, however,SOD activity(20 d) was higher 20%(high salt stress) than control(P＜0.05).POD activity(30 d) was 1(low and moderate salt stress) and 1.57(high salt stress) times of that in control(P＜0.01).CAT activity(30 d) was 2.5(P＜0.05) times of that in control under high salt stress.For Cornus stolonifera,compared with control,POD activity(10 d) were higher 85% (low salt stress),126%(moderate salt stress) and 233%(high salt stress)(P＜0.01),CAT activity(20 d) were higher 227%(moderate salt stress) and 130%(high salt stress)(P＜0.01), and APX activity(30 d) were higher 150%(low salt stress),221%(moderate salt stress) and 220%(high salt stress)(P＜0.01).In summary,Parthenocissus quinquefolia and Cornus stolonifera had to tolerance to lower salt stress and could bear the soil environment with 1.0 g·kg^-1 NaHCO₃.The tolerance against carbonate stress of Parthenocissus quinquefolia was better than that of Cornus stolonifera.