Research On Spatial Distribution Of Nutrition And Fruit Quality In Canopy And The Physiological Response To Different Plant Shaping Of Citrus

In the experiment, we reseaRCh on the spatial distribution ecological and physiological parameters in citrus canopy, and the physiological response to crown closure plant shaping and effects on fruit yield and quality, it will provide a scientific basis for tree management and high quality and high yield cultivation. In the experiment, firstly, analyses were conducted on spatial distribution of light, leaf nutrition, fruit yield and quality in canopy of 10-years-old Powell navel orange 〔 C. sinensis( L.), Powell navel orange〕, then, the effect of different tree shaping(open center shape, hedgerow shape, trunk shape) treatments on canopy characteristics, spring shoot quantity and distribution, leaf nutrition, fast chlorophyll fluorescence, fruit yield and quality of 15-year-old crown closure valencia orange were systematic studied. The main results are as follows: 1. Spatial distribution of light intensity, leaf nutrition and fruit quality in Powell navel orange canopyThrough the investigation of light intensity, leaf nutrition and fruit quality in Powell navel orange canpoy, it was found that the relatively light intensity, Chl a/b in plant canopy was upper > middle > lower, outside > inside, east > south > west > north, but the trend of leaf N, P, K and Chl a, Chl b, Chl a+b, car contents distribution was on the contrary. The fruit appearance, internal quality in outside and upper layer of canopy were better than inside and lower layer, While the fruit quality at east and south of canopy is superior to the west and north position. It showed that weak light environment will stimulate more synthesis and accumulation of photosynthetic pigments in leaves in order to maintain the necessary nutrition supply, but will weaken mineral nutrition accumulation in leaves and reduced fruit quality. 2. Study on the physiological response to tree shaping of crown closure citrus plant(1) Effects of different tree shaping treatments on photosynthetic pigments in leaves of citrus plants. From June to August, the photosynthetic pigments content in valencia orange leaves showed an upward trend, but decreased in September, Chl a/b had remained a downward trend during the test. After tree shaping of crown closure citrus plant, leaf Chl a, Chl b, Chl a+b and Car contents were obviously increased and distribution in the canopy was lower > middle > upper, inside > outside, while in the canopy of CK plants was inside > outside in middle area and outside > inside in lower area. Which showed that it could improve the photosynthetic pigments content and photosynthetic ability of the crown closure plant through tree shaping.(2) Effects of different tree shaping treatments on the contents of mineral elements in leaves of citrus plants. During the experiment, leaf N, P, K, Mg and Zn contents in spring shoots of valencia orange showed a decreasing trend, the variation trend of leaf Ca, S, Fe, Mn and Cu contents was on the contrary. After tree shaping of crown closure citrus plant, leaf N and P contents in the crown vertical dimension were significantly increased, Fe content in upper and middle area of canopy, Mn content in upper area of canopy, leaf S content in lower area of canopy, leaf N, P, Fe and S contents in inside and outside of canopy, and Ca content in lower area within crown were also improved significantly. On the whole, after tree shaping of crown closure citrus plant, leaf K, Mn and Zn contents had decreased, but the contents of N, P, Ca, S, Fe had increased. It showed that tree shaping can improve the mineral nutrition level and spatial distribution in plant canopy.(3) Effect of different tree shaping treatments on fast chlorophyll fluorescence of citrus plant. By measuring and analyzing the dynamic changes of leaf chlorophyll fluorescence in different treatments, it was found that the values of Fm, FJ, FI and Fo all decreased during the experiment, and the value of CK plants was the maximum in the same period. With the month increased, the activity parameters of unit PSII reflect center(ABS/RC, DI_o/RC and TR_o/RC) and activity parameters of unit cross sectional area ratio(ABS/CS, TR_o/CS and DI_o/CS) all decreased, but RC/CS was on the contrary. Among all the treatments, the values of ABS/RC, DI_o/RC, TR_o/RC, ET_o/RC, ABS/CS, DI_o/CS and TR_o/CS in CK were bigger than the other three processing, but the trend of ET_o/CS, RC/CS was open center shape > hedgerow Shape > trunk shape >CK. In the course of experimental observation, ψ_o、jE_o、jPo monthly increased, while jDo did opposite. The values of jPo and jDo had little difference between CK and trunk shape, but values of ψ_o and jE_o in CK were significantly smaller than the other three treatments. The Wk, VJ and Mo of all the treatments were the highest in June, VI reached to the maximum value in August, but Sm and N fell to minimum in August, at the same period, VJ, Wk, VI and Mo of CK were the largest, and Sm, N were minimum, and the electron transfer ability of leaf photosynthetic system was open center shape > hedgerow Shape > trunk shape >CK. In July and August, the RE_o/RC, RE_o/CS, jRo, yRo and dRo of all the treatments decreased, but leaf PSI related fluorescence parameters of CK were less than the other three treatments. Happy, and trunk of PIabs, PIcs and PItotal of open center shape and hedgerow shape were both increased with the extension of the month, and were significantly higher than that of CK.Through analysis and determination the spatial distribution of chlorophyll fluorescence in different processing plant canopy. It was found that the value of leaf Fo, FJ, FI and Fm in valencia orange canopy were upper > middle > lower, inside > outside, and Fo, FJ, FI values of the three tree shaping treatments were less than in the same location of CK plants, while Fm was the opposite. In the vertical dimension of crown, there was little difference in the activity of unit PSII reaction center in the leaves among different treatments, but in the horizontal dimension of canopy, leaf ET_o/RC, DI_o/RC, TR_o/RC and ABS/RC of inside crown were higher than that of outside. ET_o/RC in lower and inside of open center shape had little difference with that of CK plants, but DI_o/RC value was significantly lower than that of CK, so the activity of unit PSII reaction center in open center shape was higher than that of CK. RC/CS, ABS/CS, DI_o/RC, TR_o/CS, ET_o/CS in lower layer and inside of canopy were bigger than that in upper, middle layer and outside, ABS/CS in middle, lower layer of open center shape and hedgerow shape were less than that of CK, but ET_o/CS, RC/CS were significantly higher than CK, DI_o/CS decreased significantly. Compared with the weak light of lower layer and inside, ψ_o, jE_o, Mo and VJ in middle, upper layer and outside of the test plants were smaller, but Sm, N, jRo, yRo, dRo and PItotal were larger, the trend of photosynthetic efficiency was upper > middle > lower, outside > inside. jE_o, jRo, PIabs, PIcs 和 PItotal in lower layer and inside of open center shape, hedgerow shape and trunk shape were significantly higher than those of CK, which showed that the energy utilization rate and Photosynthetic efficiency were significantly enhanced.(4) Effect of different tree shaping treatments on the distribution of canopy spring shoots. In the experiment, spring shoots of CK plants were mostly short branches, and concentrated in the upper layer and outside of canopy. Spring shoots of open center shape were mostly short branches and middle branches, mostly concentrated in the middle layer and outside, in lower layer and inside of crown, the number of spring shoots in open center shape was significantly higher than that of the others. In lower layer and inside of hedgerow shape, spring shoots were mostly long branches, but short spring shoots in upper layer and outside of canopy were mainly for the whole tree.(5) Effects of different tree shaping treatments on canopy characteristics of plants. From June to September, leaf area index and leaf inclination angle of the tested plants showed an upward trend, while scattering radiation transmission coefficient, direct radiation transmission coefficient and photosynthetic active radiation were the opposite. In the same period, leaf area index and extinction coefficient of CK was significantly higher than the three tree shape treatments, but leaf inclination angle, scattering radiation transmission coefficient, direct radiation transmission coefficient and photosynthetic active radiation were on the contrary. Scattering radiation transmission coefficient, direct radiation transmission coefficient and photosynthetic active radiation of open center shape were largest among four treatments, light transmittance was open center shape > trunk shape > hedgerow shape >CK.(6) Effects of different tree shaping treatments on fruit yield and quality of citrus. The fruits of each treatment were concentrated in the middle and upper layer and outside of crown. Among them, yield in the upper of hedgerow shape crown was highest, which of open center shape was lowest, the middle layer of the crown in open center shape was highest and that in CK was the lowest, in the lower layer, production of open center shape was highest. No matrer outside or inside of canopy, number of fruits in open center shape was the most, yield of per plant was open center shape > trunk shape > hedgerow Shape > CK. Outside and the upper of the tested plants canopy, fruit appearance, internal quality were both better than that of inside and the lower layer. The fruit quality of open center shape was the best among all the treatments, there was little difference between hedgerow shape and trunk shape, but those were both better than CK.