Effects Of P And K Fertilizer On Vegetative Growth And Some Physiological Chatacteristics In Cymbidium Longibracteatum

Cymbidium longibracteatum'Yingansu' and C.longibracteatum 'Dahongzhusha' were cultivated hydroponically for several months in 5 levels (0 mmol-L-1-,1 mmol-L"1,5 mmol-L-1,10mmol·L-1,50 mmol·L"1) of NaH2PO4 and KCl in order to find the most suitable concentration of P and K for their growth and development and photosynthetic physiology. In this study, growth of aboveground and changes of photosynthetic characteristics, antioxidant defense system related substances and organic compounds were investigated, aimed to provide the basis of basic theoretical and systematic research, and with lagged cultivation technology about Cymbidium longibracteatum. Results showed as below:1. The two plants had the same the most suitable concentration of K to the growth of aboveground, by contrast, with different P the most suitable concentration. The results indicated that P at 1 mmol-L-1 the vegetative growth synthetic index and new budlets reach reaches the highest in C.longibracteatum var.Yingansu. however, to C.longibracteatum var.Dahongzhusha,P at 5 mmol·L"'was the most benificial to the growth of stem, the leafbud quantity and height and area's optimal concentration was 1 mmol-L-1 P, on the contrary, the leaf quantity and leaf width of leafbud reach the highest at 10 mmol-L-1 P. In addition, the ability to resist Gloeosporium orchideorum disease at Smmol·L-1 and 10 mmol-L-1 in C.longibracteatum'Yingansu' and C.longibracteatum 'Dahongzhusha' reach lowest. When the K amounts were 5 mmol-L-1, the growth synthetic index of the stem and new budlets and the ability to resist Gloeosporium orchideorum disease got best performance.2. Different P and K concentrations significantly affect the photosynthetic physiological characteristics of Cymbidium longibracteatum. The curve of Pn diurnal variation presented typical double-peak curve, and there is obvious'midday depress' phenomenon, The second peak value was lower than the first one, the trend of two in the three seasons was the same, but the curve of Pn diurnal variation of different concentration presented different trend. When C.longibracteatum'Yingansu' and C.longibracteatum'Dahongzhusha' were Respectively at 1mmol·L-1 and 5 mmol·L-1, Chl(a+b) pigments content, the daily amaounts of fixed carbon dioxide and release oxygen, the light saturation point (LSP), apparent quantum yield(AQY), the carboxylation efficiency(CE), photosynthetic rate(Pn) reaches the highest, the CO2 compensation point (CCP) were the lowest. however, When the K amounts were 5 mmol·L-1, all of the indexes reachesthe best performance.3. The activity of SOD and POD, the content of MDA, soluble protein and soluble sugar of leaf had significant differences with different treatments of the plant. The highest of POD and SOD activities, and minimum of MDA content were observed at 1 mmol·L-1 P with'Yingansu' and at 5 mmolL-1 P with'Dahongzhusha'. The optimum amounts of fertilizing of C.longibracteatum var.'Yingansu'and C.longibracteatum var.'Dahongzhusha'were both 5 mmol-L-1 K, The activity of SOD, POD, the content of soluble protein and soluble sugar got the best performance, and the the content of MDA was the lowest.