Effects of different altitudes on leaf photosynthetic characteristics and fruit quality in Myahintha mango

Abstract: 【Objective】The effects of altitude on phenological periods, leaf photosynthetic characteris-tics, fruit appearance and internal quality with Myahintha mango was studied to provide the basis for choosing the most suitable cultivation altitude range and guiding practical production of Myahintha man-go.【Methods】In the study, four altitudes (685 m, 850 m, 1034 m, 1194 m) in Lujiang town were select-ed to measure the phenological periods, leaf photosynthetic parameters, and external and internal fruit quality. 12 photosynthetic parameters, 10 fruit appearance traits and 7 internal quality traits were ana-lyzed by difference, correlation, gradual regression and path analysis.【Results】1. The altitude had an ef-fect on the flowering and fruit harvest periods of Myahintha mango. With the increase of altitude, the ini-tial flowering period, full flowering period, final flowering period and fruit harvest period of each alti-tude section were delayed 10 days. 2. The altitude was negatively correlated with water content, CO2 con-centration, atmospheric temperature, leaf surface temperature, stomatal conductance, water use efficien-cy, stomatal limitation value and mesophyll instantaneous carboxylation rate. There was no significant correlation between altitude and atmospheric radiation intensity, intercellular CO2 concentration and transpiration. Net photosynthetic rate was positively correlated with CO2 concentration, air temperature,leaf surface temperature and stomatal conductance, but negatively correlated with transpiration rate. Net photosynthetic rate and instantaneous carboxylation rate in mesophyll decreased with the increase of al-titude. Net photosynthetic rate and instantaneous carboxylation rate in mesophyll at 685 m and 850 m were significantly higher than those at other altitudes (p ＜ 0.05). The concentration of intercellular CO2 increased first and then decreased with altitude. The concentration of intercellular CO2 at altitude of 1194 m was significantly higher than that of other altitudes. The transpiration rate increased first and then decreased with the increase of altitude. The stomatal conductance at 850 m was significantly high-er than that at other altitudes. The variation of atmospheric temperature and leaf surface temperature was consistent, and the atmospheric temperature at 850 m was significantly higher than that at other alti-tudes. Photosynthetically active radiation (PAR) increased first and then decreased with altitude. The PAR at 850 m and 1034 m was significantly higher than that at 685 m and 1194 m. Path analysis further showed that the change of altitude affected atmospheric temperature, water use efficiency, CO2 concen-tration and transpiration rate, and the water use efficiency and air temperature showed negative effects on CO2 concentration and air temperature and 82.2% of these four photosynthetic factors were affected by altitude change. 3. There was a significant positive correlation between altitude and single fruit weight, pericarp weight, longitudinal and transverse diameters in fruit, fruit thickness, seed weight, seed length and width, but had no effect on seed thickness and edible rate. With the increase of altitude, the single fruit weight increased gradually, and the average fruit weight at high altitude was significantly higher than that at other altitudes. The changes of peel weight, longitudinal and transverse diameters in fruit, fruit thickness, seed weight, seed length and width as well as single fruit weight increased with the elevation. The seed thickness at 850 m and 1034 m was significantly higher than that at 685 m and 1034 m,and the edible rate was not significantly different among various altitudes. The results of path analysis showed that the single fruit weight and fruit longitudinal diameter were affected by the change of alti-tude, and 79.9% of these two variables were affected by the change of altitude. 4. Altitude was negative-ly correlated with soluble solids, total sugar, vitamin C and total acid contents. With the increase of alti-tude, the total sugar and vitamin C contents decreased. The total sugar and vitamin C contents at 685 m were significantly higher than those at other altitudes. The total acid and soluble solid contents increased first and then decreased with the increase of altitude. The protein content increased first and then de- creased with the increase of altitude, and reached the highest at 1034 m. The crude fiber content at 850 m was significantly higher than that at 1034 m and 685 m. The crude fat content decreased first and then in-creased with the increase of altitude, and reached the highest at 1194 m. Path analysis also further showed that the change of altitude mainly affected two characteristics like fruit vitamin C and total sug- ar contents, and 97.4% of two variables were affected by the change of altitude.【Conclusion】The changes of altitude had a comprehensive effect on the phenological periods, photosynthetic characteris-tics, and external and internal fruit quality. The net photosynthetic rate was the lowest at 1194 m, the fruit ripening stage was the latest, and the average fruit weight was the highest; the total acid and solu-ble solids contents at 850 m altitude were higher than those at other altitudes; the total sugar and vita-min C contents at 685 m were higher than those at other altitudes, the fruit quality at 685 m and 850 m in Lujiang town was better than that at other altitudes, but the ripening period of fruits at 1194 m was the latest. Therefore, suitable planting areas should depend upon the needs of environment and market.