Respiration rate and chemical composition of Karwinskia roots as affected by temperature

Two-year-old plants of Karwinskia humboldtiana Zucc. and Karwinskia parvifo lia Rose grown from the seeds in greenhouse were transferred to the growth cabinet and cultivated for two months under different temperature regimes ( 35/20 degreesC - the summer temperature regime, SR, and 20/5 degreesC - the winter temperature regime, WR). These temperatures were similar to the tem perature conditions in the natural areas of the species studied (Nuevo Leon , Mexico). The root respiration rate was higher in the plants cultivated un der SR than in those under WR. Roots of K. parvifolia respired faster in bo th temperature regimes than roots of K. humboldtiana. Starch content in roo ts was higher in the plants cultivated under SR, however, concentrations of the other investigated organic and inorganic compounds were higher in the plants cultivated under WR. In K. humboldtiana roots, higher concentration of reducing sugars, carbon and hydrogen were found than in K. parvifolia.