PHYSIOLOGICAL CHA.."\GES DURI NG THE GERMIKATION OF CATTLEYA AURA."\iTIACA (O RCHI DACEAE) 1

Se~s of Cattleya 011ra11t~aca grown ~ymbiotically on a medium containing sucrose as the sole source of organic carbon developed into leaf-bearing plants. Those sown on the same medium without sugar reached the protocorm stage but did not differentiate further. Cross transfers of seedlings between the two media indicated that following 21-30 days of growth on the sucrose-containing medium subsequent development may_proceed in the absence of sugar. Levels of chlorophyll and ribulose-1,5-diphosphate carboxylase were monitored and related to the ability of young seedlings to photosynthesize. A direct relationship between chlorophyll content and photosynthesis was not found. Increases in the activity of the enzyme were closely paralleled by increases in phdtosynthesis. A direct relationship was not found between chlorophyll a/ b ratios and photosynthetic capacity. Germinating seeds and seedli ngs grown in the absence of exogenous carbohydrate were unable to convert appreciable amounts of labeled acetate to sugar. Int r oduction