PHYSIOLOGY OF PHOTOSYNTHESIS IN CHIMALACATE (Viguiera dentata) IN THE ZAPOTITLAN DE LAS SALINAS VALLEY OF THE TEHUACAN BIOSPHERE RESERVE IN PUEBLA, MEXICO

Abstract

Growing interest in understanding ecological deterioration phenomena and natural restoration of native landscapes has led us to initiate a research effort on a wild species which may be instrumental in the recovery of severely disturbed ecosystems. Here we report on the basic characterization of growth and gas exchange in the perennial desert shrub known as ";chimalacate"; (Viguiera dentata) in the Tehuacan Biosphere Reserve in Puebla, Mexico. Chimalacate plants grew almost twice as tall, developed twice as many tillers, showed 54% greater dry weight, 40% greater leaf expansion rate and over 5 times as many flowers when exposed to full sun as compared to plants growing in the shade. However, shaded plants developed 48% more leaf area per plant mainly due to more leaves per plant. Optimum leaf temperature for photosynthesis at high light intensity and ambient CO2 concentration was 34°C. Light and CO2 compensation points under a controlled environment ranged between 23 and 48 µmol m-2 s-1 and between 22 and 32 µL L-1 CO2, respectively. The photosynthesis data presented indicates chimalacate is a C3 plant well adapted for growth in a hot dry climate.