Temperature dependence of guard cell respiration and stomatal conductance co-segregate in an F-2 population of Pima cotton

In Pima cotton (Gossypium barbadense L.), stomatal conductance shows a stro ng response to temperature. At high temperature (40 degrees C), the stomata l conductance of greenhouse- and growth chamber-grown leaves is three and f our times higher than that measured at lower temperature (25 degrees C), re spectively. The segregation of stomatal conductance observed in an F-2 popu lation obtained from a cross between a primitive cotton (B368) and a modern Pima line (Pima S-6) increased substantially with temperature in both ligh t and darkness. Furthermore, F-2 segregants with high stomatal conductance at high temperature were more sensitive to temperature, showing larger chan ges in conductance in response to an increase in temperature when compared to F-2 segregants having low stomatal conductance. Rates of guard cell resp iration measured in enzymatically-cleaned epidermal peels, mechanically iso lated from the same F-2 plants, showed the same temperature dependence. The temperature-induced respiration enhancement was higher in guard cells with high respiration rates. There were positive correlations between stomatal conductance and guard cell respiration rates, and between stomatal conducta nce and the sensitivity of respiration to changes in temperature. These res ults imply that guard cell respiration and stomatal conductance co-segregat e in Pima cotton plants, suggesting that guard cell respiration is a compon ent of the sensory transduction pathway controlling stomatal responses to t emperature.