Effect Of 4-PBA On The Growth And Yield Of Summer Maize Under Flooding Stress

Using Denghai662 and Zhengdan958 as the experimental materials,the flooding test was conducted in the seedling and tasseling stages of summer maize in a combination of potted and field plants.The effect of 4-phenylbutyric acid(4-PBA)on the physiological and morphological characteristics and maize yield were investigated under flooding stress.The flooding test at seedling stage was conducted indoors using potted plants.The flooding test at tasseling stage was conducted in the Science and Education Park of Henan Agricultural University located at Maozhuang.The main results are listed as follows:1.Under indoor potting conditions,compared with the non-flooded control(CK),the superoxide anion(O2-)generation rate intensified in the roots of maize seedlings under 3 or 5 days of flooding;similarly,the activities of superoxide dismutase(SOD)and peroxidase(POD)decreased,the growth of root was inhibited,total root length and the dry weight of root were decreased.However,after foliar spraying of 4-PBA before flooding,the O2-generation rate in roots decreased significantly,the activity of POD enhanced and the root dry weight increased.This indicated that 4-PBA could alleviate the inhibiting effect of flooding stress on the roots of maize seedling and enhance the growth of roots.Under normal conditions,to a certain extent,the pretreatment of 4-PBA can enhance the activities of antioxidant enzyme of root,total root length and root dry weight,but the effect was not significant.2.Under indoor potting conditions,compared with the non-flooded control(CK),the SOD activity in the leaves of flooded maize seedlings increased,the plant height,the soluble protein and chlorophyll content also decreased.However,with the foliar pre-spraying of 4-PBA,the SOD activity in the leaves was significantly enhanced;the soluble protein and chlorophyll contents and plant height increased significantly as well,indicating that 4-PBA could relieve the flooding stress on the growth of maize seedlings and increase the ability of maize seedlings to resist flooding.Under non-flooding conditions,spraying of 4-PBA significantly enhanced SOD activity in leaves.3.During the tasselling stage of field plants,the content of Malondialdehyde(MDA)in the leaves of maize after 5 or 7 days of flooding was significantly greater than that of the non-flooded control(CK);the activities of SOD,POD and CAT were significantly decreased.After pre-spraying with 4-PBA,the activities of SOD,POD and CAT in leaves of flooded plants were significantly increased,and the content of MDA was greatly decreased.This indicated that pre-spraying of 4-PBA could alleviate the damage caused by flooding on maize plants.Under non-flooding conditions,foliar application of 4-PBA had no significant effect on leaf SOD,POD,CAT activities and the MDA content.In addition,flooding stress significantly reduced the soluble protein content of leaves,while after pre-spraying with 4-PBA,the soluble protein content in leaf of flooded plants increased significantly,indicating that foliar spraying of 4-PBA could promote their osmoregulatory ability.After flooding,SPAD values on leaves of flooded plants were significantly lower than those of CK,but with pre-spraying of 4-PBA,the SPAD values were resumed to close to the normal level.This indicated that spraying 4-PBA could inhibit the degradation of chlorophyll and reduce the damage caused by flooding.Under normal growth conditions,spraying of 4-PBA had no significant effects on the SPAD values.Under flooding stress,plant height,puncture strength and crushing strength of maize were significantly lower than that of CK;the length of stem near the ground was significantly longer than that of CK.After pre-spraying with 4-PBA,the crushing strength of plants was significantly enhanced;the length of stem segments was significantly reduced and excessive stem elongation was inhibited.These results showed that foliar spraying of 4-PBA could improve the lodging resistance of maize that suffered from flooding stress to some extent.Under normal growth conditions,the effect of spraying 4-PBA on plant height,ear position coefficient and stem diameter was not obvious.The total dry matter accumulation in the aboveground parts of maize was significantly reduced during flooding,and the dry matter accumulation in stems,leaves,sheaths and grains was lower than that in CK.On the other hand,total dry matter accumulation in the shoots of the flooded plants was significantly increased after pre-spraying 4-PBA compared with that of plants pre-spraying of water.The dry matter quality of both stem and grain reached to a significant level.These results showed that foliar application of 4-PBA could alleviate the effects of flooding stress on maize growth.Besides,the length of baldness in flooded plants increased;the panicle length,ear rows,grain number per row,100-grain weight and yield of flooded plants decreased significantly.After pre-spraying of 4-PBA,the panicle length,grain number,and 100-grain weight were significantly increased by 4.88%,3.26%and 3.86%,respectively,and the yield was significantly increased by 23.70%.In summary,foliar spraying of 4-PBA on maize plants at tasseling stage can improve their ability to resist flooding,especially if the time of flooding is less than 5 days.