Abstract: Taking ‘Hanfu’ apple (Malus domestica Borkh.) as test material, this paper studied the effects of different irrigation modes, including regular irrigation (control), alternate half root-zone irrigation, half root-zone irrigation, and drought, on the photosynthetic function and antioxidant enzymes activities of apple leaves. Compared with the control, the other three irrigation modes had inhibitory effects on the leaf net photosynthetic rate (P_n) and stomatal conductance (G_s), with the effects decreased in the order of drought > half root-zone irrigation > alternate half root-zone irrigation. Alternate half root-zone irrigation, half root-zone irrigation, and drought all made the leaf chlorophyll content decreased obviously after an initial increase, with the peak on the 9th day, and the chlorophyll content was the lowest in drought treatment all along. Alternate half root-zone irrigation, half root-zone irrigation, and drought increased the leaf proline content throughout the experiment, with the highest proline content in drought treatment and the lowest one in alternate half root-zone irrigation treatment. Alternate half root-zone irrigation, half root-zone irrigation, and drought induced different changes in the leaf antioxidant enzymes activities. The SOD activity in drought treatment and half root-zone irrigation treatment increased markedly and reached a peak on the 9th day, and then decreased rapidly, while the SOD activity in alternate half rootzone irrigation treatment kept at a relatively higher level. In half root-zone irrigation and alternate half root-zone irrigation treatments, the POD and CAT activities showed a similar variation trend, i.e., increased to a peak on the 9th day, followed by a decline later. In contrast, the POD and CAT activities in drought treatment went up speedily first and remained relatively high after 9 days. All the treatments except the control increased the leaf electrical conductivity and MDA content, with the increments being the highest and reached the significant level in drought treatment, and the lowest in alternate half root-zone irrigation treatment. In short, alternate half root-zone irrigation could maintain relatively higher efficiency of photosynthesis on the basis of reduced irrigation amount, with lighter drought stress, which could realize the water-saving cultivation of fruit trees.  

Key words: tomato, vermicompost, probiotics, fruit quality, soil nutrients.