Study On Creeping Bentgrass Drought Resistance Physiological Mechanism Induced By Spermidine Pretreatment

Creeping bent grass (Agrostis stolonifera L.) is an excellent cool-season turf grass, with a soft texture, beautiful color, tolerance to low mowing, renewable and other characteristics. It is an important grass species used for planting the golf course and ornamental lawn in temperate and subtropical regions. However, their fibrous root distributions are shallow, and its drought tolerance is poor. In turf management it is an urgent need to address the problem that how to improve creeping bentgrass drought tolerance and reduce water consumption, under the situation that freshwater resources and lawn irrigation water supply shortage is increasingly serious. In this study we use the golf course wildly used creeping bentgrass cultivar Penn-A4as the test materials, spermidine (Spd) were pretreated by foliar spray in artificial drought conditions to explore the physiological mechanism of creeping bentgrass drought tolerance induced by exogenous amines. The main content of the study include three aspects:a) the exogenous spermidine pretreatment on creeping bent grass antioxidant protection; b) the exogenous spermidine on creeping bent grass endogenous polyamine content; c) the exogenous spermidine on creeping bent grass endogenous hormone content. The main conclusions are as follows:1. Exogenous spermidine pretreatment could improve creeping bent grass drought tolerance by delaying the senescence process of creeping bent grass leaves under drought stress. Relative water content was decreased continuously in both the spermidine pretreatment and without pretreatment creeping bent grass leaves. However, the former showed a slower rate, and9d later, the former relative water content was significantly higher than the latter. The chlorophyll content of the two group material also declined continuously with the stress continued, but12d later, the former chlorophyll a and total chlorophyll content was significantly higher than the latter.2. Exogenous spermidine pretreatment could enhance the antioxidant capacity of creeping bent grass under drought stress. Both the O2-generation rate and H2O2content in creeping bent grass leaves significantly increased after9d of drought stress. But the O2-generation rate and H2O2content of the pretreatment materials was significantly lower. At the same time, the activities of the four kind’s antioxidant enzymes SOD, APX, CAT and POD were significantly difference between the two group materials. In addition, the activities of SOD, APX and POD in the pretreatment materials significantly higher than the material without pretreatment at the end stage of drought, and the former CAT activity dropped below initial levels after the stress for12days, while the latter was5days later. Accordingly, the former membrane lipid peroxidation products malondialdehyde (MDA) content was significantly lower than the latter.3. Exogenous spermidine pretreatment could induce the endogenous polyamine level in creeping bent grass leaves showed a greater change. Creeping bent grass leaf putrescine (Put) content has an upward trend during stress in both pretreatment and without pretreatment materials, the former continued to increase after5d, while the latter is essentially unchanged. The former spermine (Spm) content sharply fluctuations during stress, while the latter basically saved the same level. For Spd, the pretreated material is higher than without pretreatment material during the whole stress period. Further analysis showed that the (Spd+Spm)/Put ratio of the two treatments materials showed a downward trend in drought stress early stage, while the latter is relatively stable. The ratio of pretreatment material slowly declined before the9days stress, and then stabilized. While the same ratio of without pretreatment material falling sharply in the first5d drought, and then stabilized.4. Exogenous spermidine plays a certain regulatory role on creeping bent grass endogenous growth-promoting hormone levels. Two group materials auxin (IAA) and abscisic acid (ABA) content were increased firstly and then decreased. The content of gibberellin (GA3) was changed regularly. Two growth-promoting hormones GA3and IAA content of polyamines pretreatment materials were significantly lower than without pretreatment material in the late stage of stress, but ABA content was no significant difference between the two treatments.