A new mechanism for the regulation of stomatal aperture size in intact leaves: Accumulation of mesophyll-derived sucrose in the guard-cell wall of Vicia faba
- Florida State Univ., Tallahassee, FL (United States)
At various times after pulse-labeling broad bean (Vicia faba L.) leaflets with {sup 14}CO{sub 2}, whole-leaf pieces and rinsed epidermal peels were harvested and subsequently processed for histochemical analysis. Cells dissected from whole leaf retained apoplastic contents, whereas those from rinsed peels contained only symplastic contents. Sucrose (Suc)-specific radioactivity peaked (111 GBq mol{sup -1}) in palisade cells at 20 min. In contrast, the {sup 14}C content and Suc-specific radioactivity were very low in guard cells for 20 min, implying little CO, incorporation; both then peaked at 40 min. The guard-cell apoplast had a high maximum Suc-specific radioactivity (204 GBq mol{sup -1}) and a high Suc influx rate (0.05 pmol stoma{sup -1} min{sup -1}). These and other comparisons implied the presence of (a) multiple Suc pools in mesophyll cells, M a localized mesophyll-apoplast region that exchanges with phloem and stomata, and mesophyll-derived Suc in guard-cell walls sufficient to diminish stomatal opening by approximately 3 pm. Factors expected to enhance Suc accumulation in guard-cell walls are (a) high transpiration rate, which closes stomata, and N high apoplastic Suc concentration, which is elevated when mesophyll Suc efflux exceeds translocation. Therefore, multiple physiological factors are integrated in the attenuation of stomatal aperture size by this previously unrecognized mechanism. 50 refs., 9 figs.
- OSTI ID:
- 530488
- Journal Information:
- Plant Physiology (Bethesda), Vol. 114, Issue 1; Other Information: PBD: May 1997
- Country of Publication:
- United States
- Language:
- English
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