Efecto de la disponibilidad hidrica del suelo sobre la anatomia foliar y el intercambio gaseoso de dos cultivares de yuca (Manihot esculenta Crantz)

Using the infra-red gas analysis system, the rate of CO2 uptake, transpiration, leaf conductance and water use efficiency were determined on attached leaves of cassava cv. MCol 1522 and CG 403-18, which were grown in pots left outdoors. In the stress treatment, the water was withheld from the fourth to eighth week after planting. Under water stress, the photosynthetic rates were greatly reduced at all intensities in both cv. The reduction in photosynthesis corresponded to reduction in stomatal conductance. In irrigated plants, the maximum photosynthesis was obtained at light intensity of 1400 microE/m(2) seg. On the other hand, the maximum photosynthesis in the stressed plants was reached at about 500 microE/m(2) seg. The maximum water use efficiency (mg CO2/g H2O) was obtained at 200 and 400 microE/m(2) in stressed and well- watered plants, respectively. However, cv. MCol 1522 was more tolerant to water stress than cv. CG 403-18. Under water stress, the leaf thickness in different positions on the plants in both cv. was significantly reduced (P = 0.05) and the ratio of palisade/spongy tissue was increased. These changes in leaf anatomy could be a form of adaptation to water shortage and might enhance the CO2 uptake under these conditions. (AS)