Abstract:
Elucidating the physiological response of adult apple trees under drought stress in extreme arid areas can provide a theoretical basis for scientific irrigation. Taking the mature apple trees in the oases around Tarim Basin as the research object, the drought stress test was carried out from June to August (fruit expansion period) with the maximum evaporation. The drought treatment (T1, irrigation once, irrigation amount 1500 m
3/(hm
2·times)) and the control (CK, irrigation twice, irrigation amount 1500 m
3/(hm
2·times)) were set to analyze the changes of growth physiological characteristics and the effects of fruit yield and quality of four branches (short fruiting branch, long fruiting branch, moss fruiting branch and growing branch) under drought stress. The results showed that the growth branches of drought stress treatment (T1) stopped growing on 9th August, 10 days earlier than CK (19th August), and the growth branch length of T1 (63 cm) decreased by 48.36% compared with CK (122 cm). The longitudinal and transverse meridians of T1 treatment were slightly lower than CK, but there was no significant difference (
P>0.05). After 60 days of drought stress, the daily average
Pn of the four branches was significantly lower than that of the control (
P<0.01). The short fruiting branch, long fruiting branch, moss fruiting branch and growing branch decreased by 53.00%, 57.00%, 54.49% and 62.21% respectively. The daily average
Gs was also significantly lower than that of the control (
P<0.01). The short fruiting branch, long fruiting branch, moss fruiting branch and growing branch decreased by 53.85%, 62.50%, 58.21% and 60.81% respectively. With the aggravation of drought stress,
Pn value is becoming smaller and smaller, non stomatal factors play a leading role, and the damage degree of photosynthetic mechanism is becoming greater and greater. The yield per plant after drought stress was significantly lower than that of the control (
P<0.05), but the soluble solids, VC content and pH value reflecting fruit quality were significantly higher than that of the control (
P<0.01), and the total acid content was significantly lower than that of the control (
P<0.05).The reasonable water control of apple orchard management after the fruit expansion period is helpful to the transformation of fruit trees from vegetative growth to reproductive growth, and can effectively improve the fruit quality.