Leaf senescence in two potted chrysanthemum (Dendranthema grandiflora Ramat) cultivars 'Tara' and 'Boaldi'

The effect of storage duration and temperature, cultivar, fertilizer level, and type of bud removal were tested in a series of experiments to characterize leaf yellowing in potted chrysanthemums and to elucidate the possible stresses that may induce premature leaf senescence. Boaldi leaves became brittle and easy to break under high nutritional levels, but they never developed any visual chlorosis regardless of the treatments imposed. Tara was very susceptible to prolonged dark storage (6 days at 21{dollar}spcirc{dollar}C) when plants were produced with the highest fertilizer level (300 mg N.l{dollar}sp{lcub}-1{rcub},{dollar} from 20N-4.7P-16.6K), and after storage leaves were chlorotic and wilted within a week in the interior holding rooms. Multiflowered Tara plants, in which apical buds were removed and lateral buds were allowed to flower showed a distinctive pattern of veinal clorosis, while disbudded plants, in which all laterals buds were removed, did not. Tara was very susceptible to storage at 12{dollar}spcirc{dollar}C when grown in late spring or early fall regardless of the fertilizer rate and type of bud removal. Symptoms similar to chilling injury i.e. loss of turgor and wilting were observed when the plants were unboxed or within the next few days. No symptoms of chlorosis or chilling injury were observed in experiments conducted in winter.; Dark-induced senescence of detached leaves showed that chlorophyll and total soluble proteins steadily decreased, and proteolytic activity increased in Tara during a 12-day period. In contrast, Boaldi leaves maintained the initial high chlorophyll and protein levels and did not show a significant increase in proteolytic activity. Attached and detached leaves exhibited similar senescence patterns for each cultivar. Ethylene (100{dollar}mu{dollar}l.l{dollar}sp{lcub}-1{rcub}){dollar} accelerated the rate of chlorophyll loss in detached Tara leaves but had no effect on Boaldi. These results suggest that Boaldi is a type of 'stay-green' or non-yellowing cultivar, in which genes involved in the initiation of senescence have been altered.