SUCCULENCE, CATIONS AND ORGANIC ACIDS IN LEAVES OF KALANCHOE DAIGREMONTIANA GROWN IN LONG AND SHORT DAYS IN SOIL AND WATER CULTURE

ABSTRACT

Leaves of Kalanchoe daigremontiana grown in short days in John Innes compost possessed a higher water content per unit dry weight than leaves of similar age from long-day plants. For both treatments, the older the leaf the greater the water content. The effect of short days was to reduce dry weight production. When plants were grown in water culture, the differences were less marked and there was no significant difference in water content between leaves on the same plant. It is believed that, in water culture, the plants were not subjected to so large a water stress. Calcium was the major cation in the leaf, with a concentration some three to seven times that of potassium. The concentration of sodium was low but, under certain conditions, dry weight production was reduced when this cation was not added to the medium. The total concentration of organic acids never exceeded 210–230 μquiv. cm⁻³, if the total concentration of calcium, potassium and sodium did not also reach this value. Above this concentration an increase in total acid was accompanied by an equivalent increase in the total concentration of the three cations. Such an increase was only observed in long-day plants. The results are discussed in relation to the control of dark fixation in CAM plants.