REGULATION OF LIGHTDEACIDIFICATIONIN THE LEAVES OF A SALT TOLERANT CAM PLANT KALANCHOE INTEGRIFOLIA

REGULATION OF LIGHTDEACIDIFICATIONIN THE LEAVES

OF A SALT TOLERANT CAM PLANT

KALANCHOE INTEGRIFOLIA

By
s. KHALIL*
* Botany Department, Faculty of Science, Alexandria University,

Alexandria, Egypt.

Key words: Photochemistry, CAM plant.

ABSTRACT
In the CAM plant Kalanchoe integrifolia, effects oflight intensity,
temperature and bicarbonate concentration on the light-dependent
C-transfer from the dark synthesized malic acid to starch in the light
during phase 3 ofthe diurnal CAM cycle have been studied High light
intensity and high temperature increased the rate ofmalic consumption
and subsequent starch synthesis while higher bicarbonate
concentrations were increasingly inhibitory to this C-transfer process
and may stimulate light acidification. The concentration ofbicarbonate
necessary to make acidification possible during this period ofthe light
time is dependent on the initial tissue acidity.
When acidified leaves were treated with DCMU, a decline in starch
level which amount to about 23 % ofthose ofthe untreated leaves was
observed. ‘ This indicates that decarboxylation ofmalic acid in the light
is partially stimulated by the photosynthetic C02 fixation behind closed
stomata.
Possible suggestionsfor the regulation oflight dependent C-transfer
in K. integrifolia leaves were discussed