Studies On Accumulation Of Potassium And Heredity Of Genetic Differences Among Tobacco Genotypes In The Later Growing Stage

Field and water culture experiments were conducted to study the characteristic of accumulation, reasons of reducing and the mechanism of heredity of potassium content in tobacco leaves in the later growing stage. The results were as following: 1.Potassium content was reduced with tobacco leaf senesing in the later growing stage; the range of being reduced was different in different genotypes of tobacco. 2.The analysis about accumulation ratio of dry matter and potassium content in tobacco leaves, the results of experiments about water culture, cutting root and girdling phloem of tobacco stem, indicated that the important reasons of potassium content reduced in tobacco leaves were diluting effect of accumulation ratio of dry matter higher than that of potassium content, potassium going back from above of tobacco to its root and potassium being vented from root. It also found that potassium content could be improved if overground of tobacco was mainly growing part and the senescing of tobacco leaves was delayed through the experiments of topping tobacco and spraying exdogenous hormone (IAA and CTK) on leaves, which shown root became growing center after being topped, making potassium in overground of tobacco back to root, therefore, potassium content of tobacco leaves was reduced. 3.The analysis of correlation indicated that tobacco breeding with higher potassium content has the characteristics of higher stalk height, wider stalk circumference, longer leaf and more leaf number comparatively. The correlations between potassium content and nicotin among top, middle and bottom tobacco leaves were all negative. The correlation among potassium content and malondialdehyde (MDA),superoxide dismutase (SOD), conductance ratio; and protein, solubility sugar, chlorophyl and free water/bondage water were all attained marked level, however, the essence of correlation was different: the former was negative but the latter was positive. 4.The analysis of heterosis demonstrated there were different degree heterosis in the potassium content of tobacco leaf and other correlated characters, including agriculture, physiology and biochemistry. 5.There was definite difference in the general combining ability and special combining ability in different genotypes. The differentia of potassium content of tobacco leaf in different genotypes was achieved marked level. Therefore, it could be chosen proper parents to crossbreed so that the potassium content of tobacco leaf might be improved. But the combining abilities of parents must be thought when choosing them. Moreover, it is proper for choosing tobacco plants in earlier generations to cultivate new varieties with high potassium content.