Physiological Responses Of Four Introduced Woody Species To Soil Saline And Alkali Stress In Daqing, Heilongjiang Province, China

In this paper, the responses of seedlings of Euonymus bungeanus, Lonicera maackii, Picea koraiensis and Pinus sylvestris var. mongolica under NaHCO3 stress were studied. Through this program, the tolerance scopes of woody plants refered in this research against saline and alkaline stress were tested. The main results were as follows:(1) The saline and alkaline stress tolerance of the five woody species followed L. maackii> E. bungeanus> P. koraiensis>P. sylvestris var. mongolica.With the increasing stress intensity, the relative growth increments of roots, shoots and leaves of seedlings of the five woody species expressed decresing trends as well as total biomass increments, but different species had different decresing scales. The order in decreasing scale of biomass increment of the five species followed P. koraiensis>P. sylvestris var. mongolica>E. bungeanus> L. maackii.(2) The photosynthesis was suppressed significantly in the above plants under saline and alkaline stress. It was expressed as the decrease of chlorophyll contents and net photosynthetic rate. The effects of NaHC03 stress on P. koraiensis and P. sylvestris var. mongolica were obviously larger than E. bungeanus and L. maackii. Mild stress led to a significant decrease in Pn of P. koraiensis and P. sylvestris var. mongolica,21.7% and 22.5% respectively, while it did not have significant effects on E. bungeanus and L. maackii. The decreasing scale of Pn of P. koraiensis and P. sylvestris var. mongolica larger than E. bungeanus and L. maackii under moderate and severe stress.According to the changes of photosynthesis parameters of the four seedlings, it was concluded that under lower stress intensity, The main factor leading to decreasing in photosynthesis rate of P. sylvestris var. mongolica was stomatal limitation. Non-stomatal limitation was the main factor leading to decreasing in photosynthesis rate of P. koraiensis. The main factor leading to decreasing in photosynthesis rate of E. bungeanus under mild strss was stomatal limitation, while non-stomatal limitation under higher stress intensity. L. maackii is contrary to E. bungeanus.(3) With the increasing stress time, the proline content contents in leaves of the four trees rose firstly, and then decreased. At any stage, with the increasing stress intensity, the proline contents in leaves of the four trees gradually increased. With the increasing stress time and intensity, the soluble sugar and protein contents in leaves of the four trees rose as a whole.With the increasing stress intensity, the shoot and root Na+ contents gradually increased, and K+ contents gradually decreased. Under the same stress intensity, the shoot Na+ contents and Na+/K+ ratio of E. bungeanus and L. maackii were lower than that of root, while the shoot Na+ contents and Na+/K+ ratio of P. koraiensis and P. sylvestris var. mongolica were higher than that of root. At the same time, the shoot K+ contents of the four seedlings were lower than that of root.(4) Under NaHCO3 stress, the leaves of the four trees suffered some from oxidative damage,it was testified as the increase in the MDA and H2O2 contents and electrolyte leakage rate. Compared with E. bungeanus and L. maackii,P. koraiensis and P. sylvestris var. mongolica suffed more damage.Different antioxidative enzyme and antioxidant cooperated with each other against reactive oxygen damage. E. bungeanus and L. maackii had higher SOD, CAT and APX activities than P. koraiensis and P. sylvestris var. mongolica. With the increasing stress intensity, the CAT and GR activities of E. bungeanus and L. maackii gradually increased while P. koraiensis and P. sylvestris var. mongolica gradually decreased. At the same time, the change of POD of the four trees were contrary to CAT and GR. The above results showed that the four trees had obviously different antioxidative ability.