| Ginkgo biloba is one of the most important street trees. Since urban ground covered hardening, the soil moisture of city is seriously deficient, which seriously affects the growth and survival of ginkgo. And it showed abnormal even died when drought seriously. Three-year-old seedlings of ginkgo were chosen as the research material. The pot experiment was conducted to measure the effect of light drought, moderate drought and sever drought on the water physiology, photosynthetic physiology, stress physiology of seedlings to analysis of the relationship between the level of chlorosis and the soil drought degrees with the appearance of growth performance, which provides theoretical support for the cure of chlorosis. The main conclusions were as follows:(1) The soil drought can lead to the chlorosis.The rate of chlorosis was as high as 83.33%. The most light conditions for level 1 was the soil moisture content fell to 65% of field capacity, while the most serious conditions for level 4 was the soil moisture content fell to 10% of field capacity.The tree was weak. All the treatments failed to reach the performance of death.(2) Under the drought stress, physiological changes showed before the changes on the appearance.The RWC maintained higher level between 84.45% to 86.97% under the control treament. Before the symptoms occured, the RWC down to 80.50% under the light drought stress (the soil moisture content at 65% of the soil field capacity), and the RWC down to 58.28% under the serve drought stress (the soil moisture content at 10% of the soil field capacity), a drop of 22.18%.Under the condition of drought stress, the leaf photosynthetic parameters changed obviously, the LSP droped. The Pn, Tr, Gs were significantly decline over the time. While the Ci got a trend of rise first then fell slowly, and it was still higher than the initial value in the end. On the other hand, photosynthetic parameters only fluctuated in a small range for the control group.With the extension of the time, the Fv/Fm and the Fm shared a same decreasing trend: as the stress level increaseed, the decreasing amplitude expanded. Fo nevertheless, increased along the time extension and the increasing amplitude got larger while the stress level grows.As time gone on, the Pro and MDA in the Ginkgo leaves showed an increasing trend: the degree of increase was proportional to the stress level, that was, the larger the stress level was, the more Pro and MDA increaseed. The amount of Pro growed 3 to 5 times and MDA growed 1 to 1.5 times. SOD activity and SS increased at first and followed with declines, finishing with a decrease of 31.72% to 46.69%. SS started to drop after it doubled.The height of ginkgo was mostly affected by the chlorosis under the drought stress conditions. Chlorosis also suppressed the cumulation of biomass. Comparing to the normal ones, the leading thread growth, the height growth and the biomass reduced by 50.31%, 80.00% and 53.66% respectively for the affected (level 4). Level 2 chlorosis had a serious influence on the cumulation of the biomass, while level 3 chlorosis severely restricted the ability of the ginkgo to gain energy.(3)The ginkgo were sensitive to the moisture, and the soil moisture content had certain influences on growth. The soil moisture maintain at 65%-80% is the best range for ginkgo growth, without any obnormal phenomenon, timely watering is necessary. |
PDF Full Text Request