关键词: 玉米, 幼苗, 低温, 磷吸收障碍, 碳水化合物

Abstract:

【Objective】The low temperature in maize seeding stage will lead to reduction of photosynthesis, phosphorus and other nutrient absorption, which will lead to changes in metabolites, growth retardation, or even death. This study aimed to clarify the mechanism of cold-tolerance formation in maize seedlings, and to explore the changes of saccharides and their relationship with phosphorus uptake among different maize varieties at low temperatures, it provides theoretical basis for stress-resistant cultivation of maize. 【Method】Demeiya 3 (DMY3, cold-tolerant variety) and Hongdan 6 (HD6, cold-sensitive variety) that have similar phenotype were screened out in the previous study, which were selected as research materials in this study. Maize seedlings were cultivated in pots, and 28/22 ℃ (day/night) and 15/8 ℃ (day/night) were set as control and low temperature, respectively. Samplings were taken at 0, 1, 3, 5, and 7 d after treatment starts. The changes of phenotypic indexes, such as plant biomass, and growth-related indexes, such as leaf anthocyanin phosphorus absorption rate and carbohydrate content, were measured. 【Result】(1) After low-temperature treatment, morphological indexes, such as plant height, root length and fresh weight of the two varieties, were significantly lower than those of the control. However, the root-shoot biomass ratio increased continuously. The significant differences associated with low-temperature-tolerance were found between the two varieties emerged under 3-5 days of treatment. (2) Low temperature significantly increased the content of sucrose, glucose and starch in the leaves, and most of the increasement in the low-temperature-sensitive variety Hongdan 6 were higher than that in the low-temperature-tolerant variety Demeiya 3, but the increase of glucose content was lower than that in the low temperature tolerant varieties. (3) With low temperature stress, the seedling had a tendency to increase the non-reducing/reducing sugars ratio, soluble sugar/amino acid ratio (C/N ratio) and starch/soluble sugars ratio. The increasement of temporary-storage-sugar (starch/sucrose) and monosaccharide/disaccharide ratios (glucose/sucrose) were higher in the low-temperature-tolerant variety than that in the low-temperature-sensitive variety. (4) With low temperature treatment, the rate of phosphorus uptake by roots decreased significantly, and the rate of uptake was slower in the low-temperature-sensitive variety than that in the low-temperature-tolerant variety. (5) As the treat prolongated, the Pi content gradually decreased, while the anthocyanin content kept increasing. And a negative correlation between the content of Pi and anthocyanin was observed, and the correlation was stronger in the low-temperature-sensitive variety than in the low-temperature-tolerant variety. (6) The increase of sucrose or the decrease of starch would probably reduce the accumulation of biomass, meanwhile, which induced the production of anthocyanin, as well as lots of secondary metabolites. 【Conclusion】Low temperature led to the inhibition of phosphorus uptake in maize seedlings, and the content and composition in leaves were significantly altered. At low temperature condition, the increase of sucrose content was an important cause led to anthocyanin accumulation. The increase of starch and glucose was likely active responses of plants to adapt to low temperature, while the increase of sucrose, soluble sugar, fructose and anthocyanin seemed to be passive responses. The decrease of Pi content and the morphological growth indexes on seedlings were the adverse consequences of low temperature stress, and its magnitude associated with the low-temperature-tolerance of the maize varieties.

Key words: maize, seedling, low temperature, phosphorus uptake disorder, carbohydrate