Study On The Physiological And Biochemical Characters Of Several Rootstock And Scion Combinations In Citrus

In order to study the effects of different rootstocks on the physiological and biochemical characters in citrus, the text had respectively carried on the following research of Kumquat (Fortunella margarita) and Newhall navel orange (Citrus sinensis cv. Newhall).1. The differences of the tree growth and the fruit quality between Kumquat seedling tree and Kumquat grafted on Kumquat, trifoliate orange and sour tangerine were investigated in two continuous years in Yangshuo, Guangxi. The results showed that different rootstocks had different effects on both the tree growth and the fruit quality. The seedling tree with an erect shape produced the least fruits, had the smallest fruit weight and vertical and transverse diameter, the thickest peel, the lowest titratable acid (TA) content and the highest total soluble solids/titratable acid (TSS/TA) ratio. Fruits on Kumquat had the biggest fruit weight and transverse diameter, the lightest color and the lowest peel brightness, total soluble solids (TSS) and vitamin C (Vc) content. Trees on trifoliate orange showed the worst compatibility between the scion and the rootstock, and their fruits had the thinnest peel, the highest TA content, and the lowest edible rate. Trees on sour tangerine with a vigorously growth produced the most fruits, had the deepest color and the highest peel brightness, the TSS, Vc content and edible rate, the best fruit quality; In a word, sour tangerine as the rootstock for Yangshuo Kumquat obviously had more advantages than other combinations.2. It was investigated that the effects of two rootstocks of Newhall navel orange grafted on trifoliate orange and carrizo citrange on the photosynthesis, the activity of antioxidase and the fruit quality. The results showed that:(1) The phonological variations of net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and intercellular CO2concentration (Ci) in Newhall navel orange/trifoliate orange leaf all presented a bimodal carve, with two peak occurred at the squaring stage and the color changing stage for Pn and Tr, the squaring stage and maturity stage for Gs and Ci. The phonological variations of Pn and Gs in Newhall navel orange/carrizo citrange leaf all presented a unimodal carve, the maximum value occurred at the color changing stage; the variation of leaf Tr is basically the same with that of trifoliate orange, presented a bimodal carve; however, the Ci in leaf first decreased and then increased, the minimum value occurred at maturity stage. There were differences of water use efficiency (WUE) between the two rootstocks of Newhall navel orange in different phonological phase. The WUE of the Newhall navel orange/trifoliate orange reached the minimum value of3.30μmol CO2/mmol H2O and that of the Newhall navel orange/carrizo citrange reached the maximum value of10.46μmol CO2/mmol H2O at the maturity stage.(2) The comparative analysis showed that:the Pn value of the leaf from two combinations of the Newhall navel orange had a positive correlation with the value of the WUE, RuBP enzyme carboxylation efficiency (CE), stomatal limiting value (Ls) and atmospheric CO2concentration (Ca), and most reached a significant or highly significant level; while the Pn value had a negative correlation with the Ci value, and most reached a highly significant level; there were complex relation between the value of Pn and Tr, Gs, photosynthetically active radiation (PAR) and leaf temp (TL); besides, the Pn value had no significant correlation with the relative humidity (RH) value.(3) The content of the total chlorophyll, chlorophyll a, chlorophyll b and carotenoids of the Newhall navel orange/trifoliate orange were lower than that of the Newhall navel orange/carrizo citrange, but the variations of the photosytheic pigment content in different phonological phase of the two combinations were basically the same, presenting a bimodal curve of type "M", with the maximum value at the squaring stage and the color changing stage, the minimum value at the flowering stage. The variation of the value of the chlorophyll a/b of Newhall navel orange/trifoliate orange presented a smooth curve, while that of carrizo citrange presented a flat bimodal curve of type "M".(4) The total protein concentration of the Newhall navel orange/carrizo citrange in different phonological phase was higher than that of the Newhall navel orange/trifoliate orange, but the activities of the catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) were lower than that of the latter.(5) The differences were not significant for the fruit external quality between the two combinations. Trees on trifoliate orange showed a deeper color of the peel, and the fruits were bigger, with a thinner peel, a higher juice rate and a higher content of TA. The fruits of the Newhall navel orange/carrizo citrange had the higher content of TSS and Vc, the bigger TSS/TA, and the better flavor.In a word, carrizo citrange as the rootstock has some advantages and high value in use compared with trifoliate orange.