Hierarchical cluster analysis of differentially expressed transcripts involved in each hormone pathway during senescence. A. abscisic acid, ABA; B. auxin; C. cytokinin, CK; D. brassinosteroid, BR; E. ethylene, ET; F. Gibberellic acid, GA; G. salicylic acid, SA; H. jasmonic acid, JA. The left heat map illustrates the expression profiles for transcripts in the hormone pathway; the right heat map illustrates the expression profiles of transcripts mentioned in the context of hormone. The x-axis refers to each stage of leaf development. The y-axis represents the expression levels of the genes.