Preliminary Study On Biological Characteristic And Physiological Reaction Of Citrus In Protected Cultivate Conditions

Citrus protected cultivation could control and regulate environment to a certain degree. In order to enlarge planting area and extend supply time of fresh fruit, increase economic benefits and shorten growth period etc, it is necessary to study on the physiological reaction of citrus in protected condition. Phenological period, physiology, microstructure, photosynthesis, and chlorophyll fluorescence characteristics of Newhall navel orange(Citrus sinensis Osbeck.. cv. Newhall) and Guoqing No. 1 Satsuma mandarin (Citrus unshiu Marc. cv. Guoqing No.1) planted in open filed, plastic house and glass house was studied in this paper. Aims to explore the physiological reaction of citrus under those growth conditions and offer theory basis for citrus protected cultivation. The main results obtained in this paper were as follows:1 The phenological period of plastic house was about one week earlier than that of the open field and about one month earlier than glass house, while blooming date in glass house was about 40 days earlier. To July, the times of flushing shoots were respectively twice in open field, 3 times in plastic house and 5 times in glasshouse.2 Light saturated point(LSP) of Newhall under open filed, plastic house and glass house were 552.5, 505.0 and 540.0μmol.m^-2.s^-1 while Net photosynthetic rate(Pn) were5.5, 4.6 and 5.3μCO₂mol.m^-2.s^-1 respectively; LSP of Guoqing No.1 were 1035, 990 and 995μmol.m^-2.s^-1 and Pn were 9.1, 8.8 and 8.5μCO₂mol.m^-2.s^-1 respectively. Light compensate point(LCP) of Newhall in open filed, plastic house and glass house were 29.9, 24.3 and 25.0μmol.m^-2.s^-1, while Guoqing No.1 were 77.3, 55.4 and 68.9μmol.m^-2.s^-1 respectively.3 Two peaks appeared in the curve of monthly variation of leaf Pn in Newhall and Guoqing No.1, with higher peak appearing in September.Plastic house is the proper growth condition for Guoqing No.1 in the season of high temperature and light(May to October), while Newhall suffer high temperature stress in protected cultivation. Glass house is the proper growth condition for Guoqing No.1 and Newhall in the season of lower temperature and light(November to April). 4 The monthly variated peak of leaf soluble sugar content of Newhall, planted in open filed, plastic house and glass house, appeared in July, October and October respectively, with higher peak in protected cultivation, for Guoqing No.1, it were in October, September and October respectively, with lower peak in protected cultivation.5 The curves of diurnal change of leaf Pn in Newhall and Guoqing No.1 were both bimodal curve, and there was obvious "midday rest" phenomenon. The lowest peaks of both cultivars in all treatments appeared at 14 a.m in whole day. Among the lowest peaks, plastic house's was the highest, the second was glasshouse's, and the third was open field's. Protected cultivation alleviated the degree of "midday rest", compared with open field. But for different citrus cultivar it was different which is more obvious "midday rest" phenomenon in Newhall. "midday rest" is mainly caused by the non-stomata constraint.6 Diurnal change of Fm, Fv/Fm, Fv'/Fm',φPSâ…¡and ETR in open field lower than that in protected fields. It is the greater degree of photoinhibition in open field compared with protected fields. It is shown that different ways of dissipating excess light energy, PSâ…¡reaction center inactivation in open field while reversible inactivation to the PSâ…¡reaction center and thermal dissipation in protected fields. Monthly variation of Fv/Fm andφPSâ…¡in open field lower than protected fields, especially June to September.7 In protected fields, the foliar spongy tissue and palisade tissue in the spring shoot of Guoqing No.1 Satsuma mandarin is distinctly thicker than those in open fields, while the ratio of palisade to spongy tissue in open fields is greater than that in glasshouse. In open fields, foliar palisade tissue in the spring shoot of Newhall navel orange is thicker than that in protected fields, especially in glasshouse. And the thickness of foliar palisade tissue and epidermic cells in the summer shoot of Newhall navel orange is obviously smaller in open fields. What's more, the thickness of foliar palisade tissue, spongy tissue, upper and lower epidermal surfaces, ratio between palisade and spongy tissue in the summer shoot of Guoqing No.1 are all evidently smaller in open fields.