The guard cell chloroplast: a perspective for the twenty-first century

Abstract

SummaryThe guard cell chloroplast is the site of perception of blue light and of photosynthetically active radiation, and of at least one of the mechanisms sensing CO 2 in the guard cell. The guard cell chloroplast has been the focus of intense controversy over its capacity for light sensing and photosynthetic carbon fixation, and the osmoregulatory mechanisms mediating stomatal movements. It is argued here that a primary reason behind these long-lived controversies is the remarkable plasticity of the guard cell, which has resulted in responses being generalized as basic properties when opposite responses appear to be the norm under different environmental or experimental conditions. Examples of guard cell plasticity are described, including variation of chlorophyll fluorescence transients over a daily course, acclimation of the guard cell responses to blue light and CO 2 , the shift from potassium to sucrose in daily courses of osmoregulation and the transduction of red light into different osmoregulatory pathways. Recent findings on the properties of the guard cell chloroplast are also presented, including the role of the chloroplastic carotenoid, zeaxanthin, in blue light photoreception, the blue-green reversibility of stomatal movements, and the involvement of phytochrome in the stomatal response to light in the orchid, Paphiopedilum .© New Phytologist (2002 ) 153 : 415 -424

Light signaling and plant responses to blue and UV radiations—Perspectives for applications in horticulture

“…On the short term, blue light has an effect on photosynthesis by inducing stomatal opening (Lawson, 2009;Zeiger et al, 2002). Both blue and red lights are able to promote stomatal opening, and three families of blue light photoreceptors viz.…”

Photosynthetic capacity, growth and water relations in ‘Golden’ papaya cultivated in vitro with modifications in light quality, sucrose concentration and ventilation

“…This may explain the greater transpiration in the plantlets under white light treatment (Fig. 3); the blue light may have allowed greater stomatal opening (Zeiger et al 2002). According to Johnsson et al (1976), stomatal opening is faster and more efficient under blue light as compared to red light in most species studied.…”

Programmed Cell Death in Plants: Ultrastructural Changes in Pea Guard Cells

“…Thus, the guard cells contain chloroplasts and mitochondria, whereas the basic epider mal cells contain only mitochondria. Chloroplasts of the guard cells contain the usual pigments; the electron trans port, evolution of O 2 , and photophosphorylation are pro vided by photosystems I and II [13].We have shown by light microscopy that CN − causes fragmentation and disintegration of nuclei in the cells of epidermis isolated from pea leaves. Illumination signifi cantly increased the CN − induced fragmentation of nuclei in guard cells, but not in the basic epidermal cells Abstract-Treatment with cyanide of epidermal peels isolated from pea leaves resulted in destruction of nuclei in the guard cells of stomata, which is visible with a light microscope.…”

“…Thus, the guard cells contain chloroplasts and mitochondria, whereas the basic epider mal cells contain only mitochondria. Chloroplasts of the guard cells contain the usual pigments; the electron trans port, evolution of O 2 , and photophosphorylation are pro vided by photosystems I and II [13].…”