Abstract:
In order to clarify the relationships between the leaf senescence characteristics and endogenous hormone variations in different flue-cured tobacco varieties, the middle leaves of four flue-cured tobacco varieties (Yuyan 10, Yunyan 87, K326 and NC89) with different ripening and yellowing characteristics were sampled for their variations of chlorophyll content and senescence marker genes, endogenous hormone content and related gene expression during leaf development and maturation. The results showed that under the conventional field cultivation conditions in central Henan tobacco growing areas, chlorophyll content decreased gradually with the ageing and the leaf senescence increased. The ABA content was also raised, accompanied by reduced GA3, IAA and CTK contents. The senescence rate of middle leaves of Yuyan 10 was the fastest, those of Yunyan 87 and K326 were moderate and that of NC89 was the slowest. Comparing with NC89, the ABA content in Yuyan 10 maintained a higher level with the increase of leaf age, however the contents of GA3, CTK and IAA were lower. The expressions of senescence up-regulating marker genes
CP1 and
CP23 were higher, those of senescence down-regulating marker genes
PSA1 and
MC were lower. The expressions of
NtEFE26,
NtNCED1 and
NtPR1b, which regulated ethylene, ABA and jasmonic acid respectively, were higher, while the expression of salicylic acid responsive gene
NtCHN50 were lower. The differences in the senescence characteristics of the different tobacco varieties were closely related to their hormone metabolisms, and the metabolisms of ABA, ethylene and jasmonic acid in fast-maturing varieties were strong.