Portal de Periódicos da CAPES

Stomatal responses to light in the facultative Crassulacean acid metabolism species, Portulacaria afra

1992; Wiley; Volume: 85; Issue: 1 Linguagem: Inglês

10.1111/j.1399-3054.1992.tb05260.x

1399-3054

David Lee, Sarah M. Assmann,

Phytochemicals and Antioxidant Activities

Guard cell responses to light are mediated by guard cell chlorophyll and by a specific blue light photoreceptor. Gas exchange and epidermal peel techniques were employed to investigate these responses in the facultative Crassulacean acid metabolism (CAM) species, Portulacaria afra (L.) Jacq. In P. afra individuals performing C 3 metabolism, red light stimulated an increase in leaf conductance in intact leaves and stomatal opening in isolated epidermal peels, indicating the presence in guard cells of the chlorophyll‐mediated response to light. Under a background of continuous red illumination, conductance exhibited transient increases following pulses of blue but not red light, indicating that the specific stomatal response to blue light was also operative. In contrast, in CAM individuals, conductance in gas exchange experiments and stomatal opening in epidermal peel experiments were not stimulated by red light. In CAM plants, conductance did not increase following blue light pulses administered over a range of temperatures, vapor pressure differences (VPD), ambient CO 2 concentrations and background red light intensities. These results indicate that P. afra does possess typical guard cell responses to light when performing C 3 metabolism. The metabolic pathways mediating these responses are either lost or inhibited when CAM is induced.