Effect Of Water Stress On Growth And Physiology Of Neottopteris Nidus

In this research we took the potted Neottopteris nidus as the test materials with coco fiber as the culture media by the method of controlling relative water content of the media. Through the control of different levels of water stress, the study was applied to examine the effect of water stress on the morphology indexes,physiological and biochemical indexes, photosynthetic characteristics of Neottopteris nidus so as to evaluate the effect of water stress on the growth of it. The results showed that:(一) In the morphological index.(1) As water stress time prolonged in the conditions of relative water content of coco fiber being80%-85%and95%-100%, the average daily increment of leaf length and leaf width appeared to be an"S"curve with"slow-fast-slow" growth process,mwhile the average daily increment of other treatments decreased gradually.The ratio of leaf length/width gradually increased as the time of water stress prolonged,the leaves gradually became narrow and slender and the growth of leaf area reduced gradually to reduce water evaporation and improve water use efficiency.(2) With the days of water stress increasing and the relative water content of coco fiber being80%-85%and95%-100%, the density of leaf stomatal did not change significantly, the stomatal length and stomatal width were almost at the same level of dynamic chang; while in the other treatments, the density of leaf stomatal increased, and stomatal length and stomatal width reduced. The ratio of stomatal length to width increased at first and then decreased. The stomatal area reduced to reduce evaporation by improving water use efficiency so as to maintain its normal metabolism, growth and development.(二) In physiological and biochemical aspects(1) In the conditions of the relative water content between95%-100%of the coco fiber during the whole water stress period, the total chlorophyll content,the chlorophyll a content, the chlorophyll b content and the ratio of chlorophyll a/b increased at first and later decreased. The relative water content was at a high level with little change and the cell membrane permeability increased continuously, while the proline content,MDA content,soluble protein content and activities of SOD. POD,CAT increased gradually.(2) With the relative water content of coco fiber being80%-85%and the time of water stress increasing, the total leaf chlorophyll content,chlorophyll a content,chlorophyll b content,chlorophyll a/b and cell membrane permeability,MDA content,soluble protein content increased slowly at a high level, but leaf relative water content was higher. The proline content, the activities of SOD, POD and CAT were at a low level of dynamic change.(3) As the relative water content of coco fiber was less than80%, the leaf total chlorophyll content,chlorophyll a content,chlorophyll b content and chlorophyll a/b increased first then decreased; but relative water content decreased significantly. The cell membrane permeability,MDA content showed continuous rising, while proline content and soluble protein content and the activities of SOD, POD and CAT increased rapidly. After the termination of water stress, the treatment of related indexes showed some reduction.(4) Neottopteris nidus had strong osmotic regulation system, antioxidant enzymes system and purging system. Strong osmotic regulation system could regulate osmotic pressure efficiently, keep the internal moisture, and improve water use efficiency. The antioxidant enzymes system and purging system could eliminate the radicals efficiently, allow plants to avoid the attack and destruction of free radicals so as to maintain its normal metabolism and growth and development.(三) In photosynthetic characteristics aspects.(1) In the conditions of coco fiber with relative water content between95%-100%, along with the increasing time of water stress, Pn gradually declined, Gs and Tr appear to "rise-fall-rise" Change Courses, it show "S" curve, Ci changes wre not obvious, but WUE decreased gradually.(2) The relative water content of coco fiber were between80%-85%, along with the increasing time of water stress, Pn gradually declined, Gs and Tr first decreased and then increased. Ci at a high level, It did not change significantly.(3) The relative water content of of coco fiber were less than80%, along with the increasing time of water stress, Pn,Gs,Ci and Tr gradually declined, but WUE gradually increased. After re-water, the treatment of Pn,Gs,Ci and Tr gradually increased, but WUE gradually declined.(4) In the process of higher water content, Pn declined gradually due to the non-stomatal factors at early stage of water stress, while at later stage the stomatal factors worked instead. In the process of drought stress, Pn declined gradually mainly due to the stomatal factors at an early stage of water stress, but at later stage, it was to the non-stomatal factors. Drought stress reduced Gs, Ci Pn and stomatal opening degree. The reduction of Gs could further reduce the degree of the internal water loss in leaf to try to minimize the damages to the photosynthetic organs and the whole plant due to the water stress. (四) The results indicate that Neottopteris nidus was sensitive to drought stress while less sensitive to moisture stress. The water content of80%-85%of coco fiber is optimal for Neottopteris nidus growth.