TEMPERATURE INFLUENCES ON LEAF CO2 EXCHANGE, CELL VIABILITY AND CULTIVATION RANGE FOR AGAVE TEQUILANA

Agave tequilana, a species exhibiting crassulacean acid metabolism, is cultivated in Mexico for its stem and attached leaf bases from which the distilled beverage tequila is obtained. The physiological reasons why its cultivation was mostly restricted to regions in Jalisco with m inimum air temperatures in 1996 above -4 degrees C and maximum tempera tures below 36 degrees C was investigated using plants under controlle d conditions in the laboratory. Agave tequilana was relatively intoler ant of low temperatures compared with other agaves, with poor low-temp erature acclimation and a halving of uptake of the vital dye neutral r ed by chlorenchyma cells at -8 degrees C for plants at low day/night t emperatures of 15 degrees C/5 degrees C. On the other hand, a high tem perature (55 degrees C) had only a modest inhibitory effect on cellula r dye uptake for plants grown at day/night temperatures of 35 degrees C/25 degrees C. Compared with plants grown and measured at day/night a ir temperatures of 15 degrees C/5 degrees C and 25 degrees C/15 degree s C, daily net CO2 uptake by leaves decreased 70% and respiratory net CO(2 )loss by achlorophyllous leaf bases and presumably stems increase d three-fold for plants at 35 degrees C/25 degrees C. The restricted r egions for its cultivation reflects avoidance of freezing damage at su b-zero temperatures and a daily carbon loss at day/night air temperatu res of about 35 degrees C/25 degrees C and above. (C) 1998 Academic Pr ess Limited.