Study On The Regulation Of Brassinolide On Drought Resistance Of Maize

As one of the three major crops in the world and the largest food crop in China,Maize（Zea mays）is an important food and energy source,Maize production plays an important role in ensuring food reserves.Due to the impact of global warming,increasing seasonal and regional droughts have become an important abiotic factor restricting crop growth and production,posing a continuing threat to global food security.Maize production areas in China are mainly distributed in arid and semi-arid arable areas with insufficient annual rainfall.Due to lack of water,the annual corn production has been significantly reduced.Application of plant growth regulators and their analogs can effectively reduce the damage of plants to stress and improve their resistance to stress.Brassinosteroids（BRs）is a class of sterol hormones widely existed in plants.It is known as the sixth class of plant growth regulators,It plays an important role in the processes of plant cell division and cell elongation,photopogenesis,flowering,fertility and senescence.Based on the analysis of the structural characteristics and biological activity of a series of brassinolides,they can be divided into24-epibrassinolide,28-epihomobrassinolide,and 28-homobrassinolide and 22,23,24-epibrassinolide.In this experiment we select three representative brassinolides with high activity,wide application,24-epibrassinolide,28-homobrassinolide,and 28-epihomobrassinolide.To investigate the effects of spraying the three structures of brassinolide on the optimal concentration of maize seedlings and the physiological and biochemical characteristics of maize and the expression of transcription factor ZmMYB48 under drought,and the effects of Brassinolide on maize yield under water stress were explored in the field drought shack.The effects of three structural brassinolides on maize drought resistance and their differences in application activity were compared.The main findings are as follows:1、Previous studies found that seed soaking with brassinolide can improve the vitality of maize seeds under drought conditions.This experiment found three brassinolides in 0.01、0.03、0.05 mg·kg^-1processing can obviously increase the maize seedling under drought of plant height,root length,and the ground and underground fresh weight,improve root activity,chlorophyll content and photosynthesis,enhance the capacity of reactive oxygen removal,increase content of osmotic regulation substances,reduce MDA content.The regulation effect of three brassinolides on maize seedlings under drought stress was the most obvious under the treatment of 0.03 mg·kg^-1.2、The study found that moderate drought stress can enhance the protection mechanism of maize seedlings and reduce the damage caused by drought stress.However,severe drought stress can do more damage to maize seedlings than the ability of maize seedlings to regulate,and cause light inhibition and light damage to maize seedlings,thus inhibiting the growth and development of maize.The experimental results showed that the three brassinolides treated with 0.03 mg·kg^-1could improve maize seedlings’ photosynthetic characteristics,increase the activity of photosynthetic enzymes and the expression of related regulatory genes,chlorophyll fluorescence parameters and chlorophyll content,increased protection enzyme activity and increased proline content,reduce MDA content and cell membrane permeability,improve membrane stability under different levels of drought stress.At the same time,the application of brassinolide induced an increase in ZmMYB48 expression,enhanced the regulation of MYB transcription factors in plants in response to environmental stress,and further improved the drought resistance of maize.The results show that the regulating activity of 28-high brassinolide is higher than that of 24-epibrassinolide and 28-epihombrassinolide.3、The field drought shack was used to simulate the field drought stress environment,in order to explore the regulation effect of brassinolide on maize growth and yield under water stress.The results showed that the use of brassinolide spray under drought stress increased ear length,ear thickness,ear grains,row grains,and thousand kernel weight,single fruit weight and plot yield of maize.Under moderate drought stress,the yield of the 24-epibrassinolide、28-homobrassinolide and 28-epihombrassinolide treated plot yield increased by 15.27%,30.50%and 24.11%,respectively,compared with the drought control.Under severe drought stress,the yield of plots increased by 27.67%,42.26%,and 34.22%compared to the drought control,respectively.The above results show that the use of brassinolide in the field can alleviate the effect of water stress on the growth and development of maize,improve the stress resistance of maize at seedling stage,and then increase the maize yield during harvest.In this study,the greenhouse and field simulated drought condition were used to systematically compare the differences of three structural Brassinolide on drought resistance,optimal concentration and regulatory mechanism of maize,it provides a scientific basis for improving drought resistance of maize under drought stress by scientific use of brassinolide.