Low-temperature induced changes in the ultrastructure of maize mesophyll chloroplasts strongly depend on the chilling pattern/intensity and considerably differ among inbred and hybrid genotypes

摘要

The ultrastructure and dimensions of chloroplasts in leaf mesophyll cells were quantitatively examined in three parental inbred lines of maize (Zea mays L.) and their four hybrids subjected to two types of four-week low-temperature (LT) treatment: the abrupt onset of chilling temperatures (“severe chilling”, SC) and the gradual, more moderate one (“moderate chilling”, MC). The relationship between the response of individual genotypes to one or the other type of chilling was analyzed as well as the possibility to predict the behaviour of chloroplasts in hybrids from that of their parents. Although selected parameters of chloroplast ultrastructure (e.g. volume densities of granal and intergranal thylakoids, plastoglobuli, and peripheral reticulum) and dimensions changed due to the exposure of maize plants to LT, no general pattern of such changes was found for this species due to the observed intraspecific variability. The response of some genotype to SC could not be predicted from its behaviour under MC (and vice versa) and no clear rules could be applied for the inheritance of chloroplast response to chilling in the general sense. Thus, great caution should be always taken when interpreting the results of studies aimed at the dissection of chloroplast ultrastructure as affected by LT, particularly in case such studies are made with one genotype or under one type of chilling only.