The effect of lepidimoide (Na l-4-deoxy-alpha-L-threo-hex-4-enopyranos
iduronate) and its free carboxylic acid (hereafter referred as lepidim
oic acid), on senescence in oat (Avena sativa L. Cii. Victory I) leaf
segments in the dark was studied. Lepidimoic acid inhibited loss of to
tal chlorophyll in excised oat leaf segments during the initial phase
of senescence. The loss of total chlorophyll was also retarded in the
presence of 10 mu mol/L kinetin. Lepidimoic acid preserved chlorophyll
content synergistically with kinetin. Lepidimoide (Na salt) preserved
chlorophyll content in the absence or presence of kinetin to a simila
r extent as did lepidimoic acid. These facts suggest that lepidimoide
causes, especially in cooperation with cytokinin, a retardation of lea
f senescence as characterized by the loss of total chlorophyll in the
leaves.