| Ginkgo (Ginkgo biloba L.) is a multi-value deciduous tree species for the production of nuts, timber and leaves. Understanding the growth, physiological and biochemical reaction of Ginkgo under different soil water content treatments (levels) is essential to establish various Ginkgo plantations. To determine the reactions of growth, physiology and biochemistry, one-year-old seedlings of 4 Ginkgo F1 hybrids (55, 44, 11 and 32) were used to grow in a pot under greenhouse conditions with varying soil water levels . Four soil water levels (80%(W1), 60%(W2), 40%(W3) and 20%(W4) of field capacity) were employed, and the time of treatment was 100 days. The photosynthetic characteristics, endogenous hormones concentration, absorption and allocation of nutrients, ultra-structure, growth, flavonoid and terpene lactone content were investigated. The results were as follows: 1, Soil water content had significant effects on Ginkgo's growth. Relative height growth, relative diameter at collar, biomass , and leaf are and root volume per seedling of 4 Ginkgo hybrids decreased with decreasing soil water content. Root/shoot ratio of F1 55 increased with the decrease of soil water content, however, the ratio for the treatment of 20% field capacity decreased in other 3 lines. The proportion of biomass increment distributed to root increased with decreasing soil water content, and the proportion allocated to stem and leaf decreased. 2, There were significant effects for soil water content on the photosynthetic characteristics and endogenous hormones concentration of Ginkgo. Net photosynthetic rates for F1 32 and 11 were the highest in treatment W2, and lowest in treatment W4. Transpiration rate, stomatal conductance and intercellular CO2 concentration of 4 F1 hybrids decreased with decreasing soil water content. Fluorescence of steady state of leaf of 4 hybrids increased with decreasing soil water content, but the light-adapted fluorescence maximum, electron transfer rate and PSâ…¡quanta efficiency decreased. 3, Ultrastructure of leaf of Ginkgo was significantly affected by soil water content. At the soil water levels of W1 and W2, mesophyll cells and karyon were na (u?)tural, and membrane of karyon and lamlla of chloroplast were clear, and there were a few osmiopilic globules and starch grain in the chloroplast, and there were black substancec of high electron density in ectoblast of chloroplast, membrane of karyon and cell wall. At the soil water levels W3 and W4, membrane of karyon of 4 l hybrid dissolved, and a great number of chloroplast became thicken, and some lamlla of chloroplast disappeared; however, osmiopilic globules increased obviously. 4, There were significant effects of soil water content on flavonoid, terpene lactone and endogenous hormones concentration of l Ginkgo leaf. For example, the quercetin, kaemplerol, isorhamnetin and total flavonoid concentration for hybrid 11 increased with the decrease of soil water content, and ginkgolide A, B, C and bilobalide of the lines 55 and 44 also increased with decreasing of soil water content, and GA, IAA and ZT concentration of Ginkgo leaves decreased with decreasing of soil water content, but ABA concentration increased. 6,There existed significant effects for soil water content on nutrition element concentration of the Ginkgo leaf. Total N concentration of root of 4 lines increased with decreasing of soil water content, but total N concentration of stem and leaf increased at the very beginning of the experiment , then decreased (W4). Total P concentration of stem and leaf of 32 and 11 lines decreased with decreasing of soil water content, and total Ca concentration of stem of 44, 55 and 11 lines increased with decreasing of soil water content, the total Cu concentration decreased. The total K concentration of root, stem and leaf of 4 lines decreased with decreasing of soil water content, but the total Mn, Mg and Zn concentration increased.
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