Effects Of Low-temperature Stress On Maize Root Physiological Characteristics And Hormone Metabolism

Maize is the first-largest grain crop of Heilongjiang Province,which had given rise to the first in China of the area sown. It’s output takes more than 40% of the all province outputs.Low-temperature in spring is one of the main limiting factors for maize yield in Heilongjiang Province. We choose different species maize in cold resistance, to discuss the effect of low temperature on the change of characteristics,membrane structure,enzyme activity,endogenous hormones and metabolite of the root seedling growth. The result is help to analyze the root differ in different cultivars in different temperature, to provide technical reference in agricultural production, to provide technical reference for production on the screening of cold resistance varieties, to provide the theory basis for improve the level of resistance to cold, further studying physiological mechanism of maize lay the foundation.The experiment was carried on the experimental plant base in Northeast Agricultural University from 2013 to 2014, there are three virietious, Zhengdan958(cold resistance type),Xianyu335(middle type), Fenghe1(sensitivity type) were investigated at diurnal temperature of20℃/11℃(ck)、18℃/9℃、16℃/7℃、14℃/5℃ for 2,4,6,8,10 days. We study the change of root characteristics, cell membrane permeability, antioxidase activities, endogenous phytohormone.Later,selected cold resistance type(zheng 958), under 14/5 ℃ temperature,treatment 2,4,6,8 days after 1 day in normal temperature, analyzing the change of the root tip organelles and metabolomics, the experiment result indicate:With increasing temperature stress,RDW,RL,SA,RLD,DRWD growth rates were lower,conductivity were higher, the root almost stops growe at 5℃.The inhibitory effect on root and the root cell membrane permeability showed Fenghe1>Xianyu335>Zhengdan958. The experiments showed that low temperature could inhibit the growth of root, increase the root of the cell membrane permeability.Cold resistance varieties showed better root growth, relatively stable root plasma membrane system and a low permeability.The results showed that SOD and POD activities were Zhengdan958>Xianyu335>Fenghe1,MDA content showed Fenghe1>Xianyu335>Zhengdan958. With a prolonged stress under different temperature treatment,the activity of SOD,POD and the content of MDA in relative comparison are on the rise. The content of IAA changed insignificantly, the content of GA was decreased,which indicated that cold resistance type had higher ability to remove free radical and resulting toreduce the damage of membrane and keep plant metabolic. As low temperature inhibited the growth of root system, endogenous hormone adjustment could keep it grow normally, which showed that resistant varieties had strong resist-ability to low temperature and ABA played a key role in relieving stress damage.In the low temperature cold resistance exercise for 2,4,6and 8 days after the recovery one day,cytoplasm membrane keeps the whole,the nucleus,organelles,vacuole start art mechanism, which did not broken. Cold exercise 6 days after 1 day recovery, a part of organelles appeared damage phenomenon, but the plasma membrane is still intact. Cold exercise 8 days after 1 day recovery, cell plasmolysis, mitochondria decreased, dissolve phenomenon in a main organelles, vacuoles near with the plasma membrane, and be connect with the plasma membrane invagination. Mitochondria showed more stability than other organelles in recovery after low temperature stress. The cell physiological disorders, part of the structure is destroyed, need longer time to recover.It was detected 349 species metabolites in the root of maize. 101 species of them have significant difference.The results showed that in the root tip the contents of Pipecolinic acid,caffeic acid,5-hydroxytryphophan was changed at the early chilling stress,while proline,phenylalanine,asparticate,citrulline,Norleucine,creatinedegr,xylose,1-Kestose,Glucose-1-phosphate were induced significantly by the low temperature stress to maintain the osmotic homeostasis. In addition,including ethanol amine, dihydroxyacetone, recovery was also involved in adversity stress reaction.Zhengdan958 in 8 days later 1 day recovery, variations in the metabolites of significant difference is bigger, It can be inferred that through own adjustment to start art mechanism.