冠层温度多态性小麦的性状特征

冷型小麦的冠层温度 (体温 )和对照品种相比具有持续偏低 (或相当 )的特征 ,暖型小麦的冠层温度则具有持续偏高的特征。一般小麦材料和生产上使用的大多数品种与上述特征有异 ,其冠层温度突出地表现为多态性 ,即有的年份温度高低不一 ,有明显波动 ;有的年份温度持续偏低 ,似冷型小麦 ;有的年份温度持续偏高 ,似暖型小麦。与此类小麦的温度多态性相伴随 ,其它一些重要性状也有较明显的多态性表现 ,即在环境优良、环境指数较高时 ,它们的叶片功能期、蒸腾速率、净光合速率和籽粒饱满指数等重要性状趋向于代谢功能较好的冷型小麦 ;在环境恶劣、环境指数较低时 ,它们的上述性状则趋向于代谢功能较差的暖型小麦。这类小麦性状随环境条件的明显摆动构成了长期以来小麦产量不稳的生态生理基础。欲使小麦产量稳步上升 ,转换小麦温度型 ,逐步实现品种冷性化是条有希望的途径。

The Specific Characteristics of Wheat With Polymorphic Canopy Temperature

Studies show that there exists a difference of canopy temperature (plant temperature) among different wheat genotypes in locations characterized by the completely identical climatic, soil and cultural conditions of any agro ecological regions. Wheat varieties whose canopy temperatures are close to or consistently lower than that of check variety, being the dominant one in the region for a long time during kernel filling and maturing period are named as cold type wheat; while wheat varieties whose canopy temperature are consistently higher than that of check variety are named as warm type wheat. Some important characteristics of cold type wheat are distinctly different from and superior to those of warm type wheat. The differences of canopy temperature and biological characteristics between cold type wheat and warm type wheat are significant and they all show clear monomorphism. Wheat materials and most cultivars are different from cold type wheat and warm type wheat and they show strikingly polymorphism in canopy temperature, that is to say, there are canopy temperature fluctuation, consistently lower canopy temperature like cold type wheat and consistently higher canopy temperature like warm type wheat in different years. The polymorphism of canopy temperature goes well with the polymorphism of other important characteristics, such as leaf functional duration, transpiration rate, net photosynthetic rate and kernel plumpness index, etc. The state closely relates to the environmental conditions especially weather conditions, and not occurs stochastically. The environmental conditions can be evaluated by environmental index. Environmental index for kernel filling and maturing period in one year can be estimated by the mean 1000 kernel weights of the wheat materials used in the trials every year, and the environmental conditions are measured in 5 levels according to the variability of the environmental index. The frequencies of leaf functional duration, depauperation of transpiration rate, depauperation of net photosynthetic rate, and kernel plumpness index of wheat materials and most cultivars above mentioned close to those of cold type wheat, were 71%, 67%, 67% and 46% respectively, in a production year with good weather conditions and high environmental index; while in a production year with very poor weather conditions and low environmental index, the frequencies declined greatly to only 46%, 37%, 16% and 19%, respectively. On the contrary, the frequencies of above mentioned traits of the same wheat materials close to those of warm type wheat were significantly lower than those of the materials close to those of cold type wheat in a production year with advantageous weather conditions (11%, 33%, 33% and 15%), while in a production year with very poor weather conditions, the frequencies rose greatly to 40%, 63%, 84% and 48%, respectively. That is to say, characteristics of wheat materials and most cultivars tend to those of cold type wheat with strong metabolic functions under advantageous environmental conditions and tend to those of warm type wheat with weak metabolic functions under very poor environmental conditions. The obvious variations of characters of wheat may be the most important biological reason resulting in the strong fluctuation of the yield of most wheat cultivars with weather variations for a long time. To improve wheat temperature types may be an important approach to obtain high and stable yield, that is to say, breeding cold type wheat varieties in batches gradually and replacing old wheat cultivars, which vary intensely in characters and are widely adopted in wheat production, and making canopy temperature and characteristics of all wheat varieties to get typical characteristics of cold type wheat. A great lot of work must be done in order to achieve this.