Abstract
Summary Plants of Kalanchoe pinnata (Lam.) Pers. were grown in the glass chamber of a phytotron in high-light (16-23 mol photons m -2 day -1 ) and in the shade (0.8-2.1 mol photons m -2 day -1 ) respectively, without or with nitrogen nutrition (12 mol m -3 NO 3 - in irrigation solution) and well watered or droughted for 18-22 days (high-light) and 26 to 32 days (shade) respectively, prior to measurements and analyses. Part of the high-light plants were transferred to the shade and part of the shade plants to high-light before measurements. Gas-exchange (H 2 O-vapour, CO 2 ) was measured and contents of total leaf nitrogen, chlorophyll a and b and carotenoids were analysed. Both high-light and low-light grown plants showed typical CAM gas exchange. When high-light plants were transferred to the shade under all conditions diurnal net CO 2 -balance was negative. Shade plants transferred to high-light greatly increased their daily net CO 2 -uptake, particularly by extended CO 2 -fixation at high rates in the light period, if supplied with H 2 O and N. Thus, shade plants were very successful in high-light provided N and H 2 O were not limiting. Shade adaptation of shade-plants as compared to high-light plants was indicated by higher absolute chlorophyll and carotenoid contents and lower chlorophyll a/b as well as lower CO 2 -uptake to chlorophyll (a + b) ratios. The results show, that the factors irradiance, nitrogen-nutrition and water-availability interact in eliciting flexible responses of the photosynthetic mechanism in the constitutive CAM-plant K. pinnata . Highlight plants were not shade tolerant; low-light plants were shade tolerant but not shade demanding.
Published Version
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