| The ability of plants to absorb water and nutrients depends largely on the structure and function of their roots.Root traits are more correlated with drought resistance than over ground traits,and are key factors in maintaining crop yield under drought conditions.Root traits such as root length,surface area,volume,average diameter and lateral root density are considered as key traits to improve plant productivity under drought conditions.Therefore,it is very important to understand the mechanism of root regulation for the improvement of drought resistance of crops.In addition to genetic engineering,various other strategies have been used to improve plant abiotic resistance.Studies have shown that melatonin plays an important regulatory role in controlling root growth and development and can enhance plant stress resistance,but its specific manifestations and underlying mechanisms are still poorly understood.In this paper,two maize varieties(CIMBL55 and SHEN5003)were first used to study the response of root phenotype and early transcription to drought stress.By observing the survival rate and photosynthetic efficiency of maize seedling stage and vegetative stage,it was proved that CIMBL55 and SHEN5003 were drought insensitive and drought sensitive genotypes,respectively.Based on the root image results,the root configuration of CIMBL55 is significantly different from that of SHEN5003,and the root system of CIMBL55 is long and stout,with more lateral roots and seed roots.Further studies on dynamic transcriptome of primary root and seminal roots of seedlings under PEG induced treatment,combined with differential gene expression,showed that the expression of antioxidant defense related genes of CIMBL55 was stronger and the proportion of genes responding to drought stress was higher.Based on the analysis of root phenotype and transcriptome,the important root structure and drought stress response gene network of maize were determined.Considering that melatonin can promote root development and improve drought resistance of plants,this paper further studied the effects of direct addition of melatonin and seed embedding of melatonin on root development and drought resistance of maize B73.In this study,the effects of melatonin with the root-irrigation method on the root system and growth in maize seedling under drought stress were investigated.The results showed that the plants treated with melatonin had more roots,and the root length,surface area,volume and number of lateral roots were higher than the plants treated with melatonin.the effects of melatonin with soaking seed method on the antioxidant system and photosynthetic machinery in maize seedlings under drought stress were investigated.\ The results showed that under drought stress,the seed-soaking melatonin of plants grew better than those without melatonin,showing higher photosynthetic rate,stomatal conductance and transpiration rate,better antioxidant enzyme activity,and lower active oxygen and malondialdehyde content.Comprehensive description of root phenotype and physiological and biochemical data confirms that melatonin promotes plant root development,reduces oxidative damage,alleviates photosynthesis inhibition,improves plant water status,and increases plant drought resistance.A rich root system is useful to improve the water use efficiency of crop varieties and can improve the drought resistance of plants.Melatonin can improve the drought resistance of plants by promoting the root development of maize.These results will provide valuable resources for a better understanding of maize drought resistance related to root system architecture(RSA),and determine that melatonin can be used as a seed pre-treatment agent to improve crops drought resistance at seedling stage. |
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