Photosynthesis in Sitka spruce (Picea sitchensis – Bong. – Carr.) VI. Response of stomata to temperature
by Neilson R. E., Jarvis P. G. (1975)
University of Edinburgh, Scotland
in J. Appl. Ecol. 12: 879-891 – DOI: 10.2307/2402096
(1) The steady-state stomatal conductance (ks) of illuminated needles of Sitka spruce was found to depend on the current leaf temperature, and the previous growth temperature. The effects of temperature varied with the time of year.
(2) ks of illuminated needles was maximal at needle temperatures between 0 and 15 ⚬C, depending on the time of year. Values of ks were lower at temperatures below 5 ⚬C in summer (0 ⚬C in winter) and above 15 ⚬C in summer (10 ⚬C in winter).
(3) Lower values of ks at high temperatures were partly the result of higher leaf-air vapour pressure differences (VPD), caused by the higher temperatures, and partly the result of an effect of temperature independent of VPD. VPD was not implicated in the low values of ks at low temperatures.
(4) Stomatal conductance was insensitive to the mean intercellular space CO2 concentration (Ci) between 0 and 30 ⚬C. Thus the different values of ks at different temperatures could not be attributed to changes in Ci resulting from different rates of photosynthesis.
(5) Stomatal conductance was considerably reduced on the day following a 1 h exposure to -5 ⚬C in summer and autumn, but not in winter. This effect could not be attributed to a rise in Ci or in VPD.
(6) Seedlings grown for three months at 18 ⚬C day and 15 ⚬C night temperature had higher values of ks than those grown at 13/10 ⚬C or 8/5 ⚬C between 5 and 20 ⚬C but not at 0 ⚬C and below. These differences could not be attributed to differences in Ci or VPD.
(7) Possible mechanisms by which temperature can influence ks are discussed.