Low and High Temperature Influences on Cacti

Abstract

The low and high temperature extremes leading to tissue damage were examined for various species of cacti. For Opuntia bigelovii, uptake of a neutral red stain by its chlorenchyma cells was 50% inhibited by a 1-hour treatment at -7°C or 53°C, indicating the temperature limits leading to impairment of membrane function. The low and high temperature treatments leading to 50$ inhibition of nocturnal acid accumulation by this CAM succulent were -4°C and 44°C, respectively. Cold hardening leading to a decrease in the half-inactivation temperature for stain uptake averaged 0.5°C per 10°C decrease in environmental temperature for nine species of cacti. Heat hardening was much greater, 4.3°C increase per 10°C increase in environmental temperature. More negative osmotic potentials were correlated with greater heat sensitivity for 0. bigelovii, e.g., a 1.0°C decrease in the high temperature for half-inactivation of stain uptake occurred per 0.6 MPa decrease in osmotic potential. For Coryphantha vivipara, the low temperature for half-inactivation of stain uptake was essentially uninfluenced as the photoperiod was varied from 3 to 21 hours.