Effects Of Water Stress On The Photosynthesis Physiological Index Of Apple-pear Tree

Effects of water stress on the photosynthesis physiological index of field Apple-pear tree and the potted Apple-pear and stock were studied. The result showed that as far as be concerned the field Apple-pear, annual change trend of Pn and PAR take on "two-peak curve", the same to diurnal changes of Pn , and "midday depression" drastically under field. The diurnal changes of PAR appeared that "parabola"; drought and water affect Pn reduce in different degree, the former decreased obviously Pn, Pn came to the lowest after 60d the latter decreased during the early period and increased during the late period, covered grass was the best; chlorophyll content of covered grass and water was higher than CK, drought was revered; soluble sugar content of drought increased and water decreased, after short period resume all regained slowly; proline(pro) content of drought increased drastically from 18th to 28th ,what's more, pro content of drought and water was sensitive and higher than CK, after short period resume drought can't regain; SOD activities increased before decreased, those of drought and water were higher than OK, covered grass increased steadily and the lowest than others; MDA content .increased and order was drought>water>covered grass; covered grass were qualities in appear and single quantities tree, so we recalled that covered grass was the best.For the potted Apple-pear and Shanli ,Pn decreased with water stress time and order was sever>moderate>mild water stress, came to the lowest after 35d , after short period resume sever can't regain; chlorophyll content, water potential decreased and order was sever>moderate>mild water stress, after short period resume sever regained slowly, soluble sugar content and SOD activities decreased after increased increased order was sever>moderate>mild water stress ,after short period resume all regained, but SOD activities of sever was lower than OK; proline (pro) content increased drastically during the early period, what's more, pro was sensitive that mature tree(28d) was later than little tree(11d);MDA content increased and order was sever>moderate>mild water stress, after short period resume sever can't regain. Effects of water on Apple-pear were greater than those of shanli.