Comparative Study On The Photosynthetic Characteristics And Physiological Effect Of Fuji Apple In Different Altitude Of Loess Plateau

This experiment selected five altitudinal gradient(1340m、1483m、1595m、1703m、1980m) of Fuji apple as the research object. Measure the leaf structure, daily variation of net photosynthetic rate, transpiration rate, photosynthetic response curve, chlorophyll, branches enzymes levels, fruit quality at full fruit period, etc. Results showed that:1. The photosynthetic characteristics changes of red Fuji apple under different altitude. The net photosynthetic rate of leaves increased with increasing altitude, Pn at altitude of 1980 m and 1703 m was significantly higher than other three altitude. Compared with an altitude of 1340 m, 1483 m and 1595 m, Pn at altitude of 1980 m were respectively increased by 37.7%, 20.8% and 17.5%.Transpiration rate(Tr) and stomatal conductance(Gs) all increased with the rising of altitude, and at an altitude of 1980 m was significantly greater than other elevation. Daily variation of photosynthetic parameters, the diurnal variation of Pn shows bimodal curve, To reach the maximum before and after 10 AM, the second peak at 14 o ’clock. The average of Pn throughout the day increaseed as the altitude rises. Daily variation of transpiration reducing after rising first, peaked around noon.2. The chlorophyll fluorescence parameters changes of red Fuji apple under different altitude. Initial fluorescence(F0) reducing after rising first as the altitude increases, F0 at an altitude of 1703 m and an altitude of 1980 m were significantly less than other elevation. Fm showed a trend of increase with increasing altitude, Fm at altitude of 1980 m and 1703 m is significantly higher than other three altitude. Fv/Fm increases first and then decreases with the increase of altitude, Fv/Fm at an altitude of 1980 m, 1703 m and 1483 m is significantly higher than at an altitude of 1340 m and 1595 m. Diurnal variation of Chlorophyll fluorescence parameters, daily variation of F0 showed decreasing trend after first increases, To reach the maximum before and after 13 o ’clock. Average decreases with the increase of altitude. The diurnal variation of the Fm quite gentle, slow rise after increases quickly before 10 o ’clock. Fm At an altitude of 1483 m and an altitude of 1595 m are less than the other three elevation throughout the day.3. The physiological index of leaves changes of red Fuji apple under different altitude. The leaf area reduced as the altitude rises, leaf area at an altitude of 1340 m was significantly greater than other elevation. Stomata density showed a trend of first increases and then with increasing altitude, stomata density at an altitude of 1483 m is the largest. The ratio of dry weight/fresh weight reducing after rising first as the altitude increases, the ratio at an altitude of 1703 m is significantly greater than other altitude, the ratio at an altitude of 1980 m is minimum. Leaf thickness, palisade tissue thickness, ratio of grid sea thickness of upper and lower epidermis, and the main vein catheter largest diameter are increased with increasing altitude. POD, SOD, CAT content both increase with the rising of altitude, POD and CAT at an altitude of 1980 m were significantly greater than other elevation. Pro content showed a trend of slow increase with increasing altitude, there is no significant difference between the other altitude.4. The fruit quality changes of red Fuji apple under different altitude. Single fruit weight showed a trend of decrease after the first increase with the increase of altitude, at an altitude of 1483 m the weight of the biggest, up to 284 g. Fruit hardness, vitamin C(Vc) and titratable acid content showed a trend of gradual increase in the rising of altitude, the fruit hardness between 8.82 ~ 11.24 kg/cm2, fruit hardness, Vc and titratable acid content at an altitude of 1980 m are significantly greater than other elevation. The fruit soluble solids performance first increases then decreases with increase of altitude, soluble solids content at an altitude of 1980 m is significantly smaller than other elevation. Fruit peel cyanine glycosides and protein content showed a trend of reducing after rising first with the increase of altitude,both the highest content of at an altitude of 1703 m and the lowest levels at an altitude of 1340 m.