Research On Responses Of Apple Dwarf Rootstocks To Water Stress

Apple is one of the main fruit species in china, and water stress is the important factor to limited its production and quality. Dwarf culture is the trend of apple cultivation now, so using apple dwarf rootstocks is one of the important way to realize dwarf and close spacing culture in china; meanwhile the roots of stocks have great influence on apple drought tolerance, and selecting the dwarf rootstocks of higher drought tolerance not only realize the dwarf culture but also solve the problem of greater water demand, so it is the important way to realize apple water-saving cultivation.For studying physiological characteristics of drought resistance in apple dwarf rootstocks and evaluating the responses of commonly used apple rootstocks in production to water stress primarily, this experiment studied the effects of light, medium and heavy water stress on different apple dwarf rootstock by solution culture and pot culture with the tissue culture seedling, meanwhile having a comprehensive evaluation with membership function for the drought resistance .The results are summarized as below:1 Light water stress witch the hydroponics in the solution culture adding 10%PEG6000 and pot culture giving 600mL water promoted the growth of apple rootstocks, every rootstocks had new leaves and new roots obviously except B9 in the solution culture experiment, and net photosynthesis of leaves was higher than the comparison during early stage in the pot culture experiment. Medium and heavy water stress inhibited the growth significantly, and it appeared different injury symptoms with the prolonging of time.2 The photosynthesis parameters of rootstocks appeared similar dynamic regularity with the prolonging of time in the pot culture experiment . The photosynthesis parameters was higher during early 20 day, then decreased to a low level and maintained it after a month, and increased with the harmful leaves abscission during later stage.3 The net photosynthesis rate, transpiration , stomatol conductance and chlorophyll content of apple rootstocks were decreased under water stress, the decrease range was small under the light water stress but large under the medium and heavy water stress. Different apple rootstocks had different water use efficiency , but light water stress increased the water use efficiency.4 The leaf water potential was low and relative water content of leaves was high under the light water stress, so the apple rootstocks did not appeared water deficiency. As stress increase, the leaf water potential and relative water content of leaves decreased, the apple rootstocks appeared water deficiency. The proline content of leaves increased under water stress, and the proline accumulation amount had great difference in different apple rootstocks under different degree water stress.5 The relative electric conductivity and malondiadehyde content of leaves increased and membrane permeability increased in apple rootstocks under water stress, as stress increase, membrane permeability increased gradually. The higher drought resistant rootstocks had less increase in relative electric conductivity and malondiadehyde content, but the weaker drought resistant rootstocks had a greater increase.6 The drought resistance of rootstocks from high to low is P22> P59,SH28>M26,B9 under the light water stress, and P22>B9>P59>M26>SH28 under the medium water stress ,and B9>P59>P22>M26 under heavy water stress in the solution culture experiment, and the SH28dry rot to dead .7 The drought resistance of rootstocks from high to low is SH17>SH40>SH38>M26>SH28 under the light water stress, and SH40>SH17>SH38>M26>SH28 under the medium water stress ,and SH17>SH40,SH38>M26>SH28 under heavy water stress in the pot culture experiment.