Abstract
Conductance for water vapor, assimilation of CO2, and intercellular CO2 concentration of leaves of five species were determined at various irradiances and ambient CO2 concentrations. Conductance and assimilation were then plotted as functions of irradiance and intercellular CO2 concentration. The slopes of these curves allowed us to estimate infinitesimal changes in conductance (and assimilation) that occurred when irradiance changed and intercellular CO2 concentration was constant, and when CO2 concentration changed and irradiance was constant. On leaves of Xanthium strumarium L., Gossypium hirsutum L., Phaseolus vulgaris L., and Perilla frutescens (L.), Britt., the stomatal response to light was determined to be mainly a direct response to light and to a small extent only a response to changes in intercellular CO2 concentration. This was also true for stomata of Zea mays L., except at irradiances < 150 watts per square meter, when stomata responded primarily to the depletion of the intercellular spaces of CO2 which in turn was caused by changes in the assimilation of CO2.
Stomata responded to light even in leaves whose net exchange of CO2 was reduced to zero through application of the inhibitor of photosynthetic electron transport, cyanazine (2-chloro-4[1-cyano-1-methylethylamino]-6-ethylamino-S-triazine). When leaves were inverted and irradiated on the abaxial surface, conductance decreased in the shaded and increased in the illuminated epidermis, indicating that the photoreceptor pigment(s) involved are located in the epidermis (presumably in the guard cells). In leaves of X. strumarium, the direct effect of light on conductance is primarily a response to blue light.
Stomatal responses to CO2 and to light opposed each other. In X. strumarium, stomatal opening in response to light was strongest in CO2 free air and saturated at lower irradiances than in CO2 containing air. Conversely, stomatal closure in response to CO2 was strongest in darkness and it decreased as irradiance increased. In X. strumarium, P. vulgaris, and P. frutescens, an irradiance of 300 watts per square meter was sufficient to eliminate the stomatal response to CO2 altogether. Application of abscisic acid, or an increase in vapor pressure deficit, or a decrease in leaf temperature reduced the stomatal conductance at light saturation, but when the data were normalized with respect to the conductance at the highest irradiance, the various curves were congruent.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Cowan I. R., Farquhar G. D. Stomatal function in relation to leaf metabolism and environment. Symp Soc Exp Biol. 1977;31:471–505. [PubMed] [Google Scholar]
- Dubbe D. R., Farquhar G. D., Raschke K. Effect of abscisic Acid on the gain of the feedback loop involving carbon dioxide and stomata. Plant Physiol. 1978 Sep;62(3):413–417. doi: 10.1104/pp.62.3.413. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Farquhar G. D., Dubbe D. R., Raschke K. Gain of the feedback loop involving carbon dioxide and stomata: theory and measurement. Plant Physiol. 1978 Sep;62(3):406–412. doi: 10.1104/pp.62.3.406. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Good N. E. Inhibitors of the Hill reaction. Plant Physiol. 1961 Nov;36(6):788–803. doi: 10.1104/pp.36.6.788. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hsiao T. C., Allaway W. G. Action Spectra for Guard Cell Rb Uptake and Stomatal Opening in Vivia faba. Plant Physiol. 1973 Jan;51(1):82–88. doi: 10.1104/pp.51.1.82. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Scarth G. W. MECHANISM OF THE ACTION OF LIGHT AND OTHER FACTORS ON STOMATAL MOVEMENT. Plant Physiol. 1932 Jul;7(3):481–504. doi: 10.1104/pp.7.3.481. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wong S. C., Cowan I. R., Farquhar G. D. Leaf Conductance in Relation to Assimilation in Eucalyptus pauciflora Sieb. ex Spreng: Influence of Irradiance and Partial Pressure of Carbon Dioxide. Plant Physiol. 1978 Oct;62(4):670–674. doi: 10.1104/pp.62.4.670. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Zeiger E., Hepler P. K. Light and stomatal function: blue light stimulates swelling of guard cell protoplasts. Science. 1977 May 20;196(4292):887–889. doi: 10.1126/science.196.4292.887. [DOI] [PubMed] [Google Scholar]