[Physiological and microclimatological changes induced on tomato by a floating cover] | Cambios fisiologicos y microclimaticos inducidos en jitomate por una cubierta flotante

English. The use of floating covers such as Agribon on tomato (Lycopersicon esculentum Mill.) plants has prevented the growth inhibition observed when planted during the autumn winter season, in the subtropical low, lands of the State of Morelos, Mexico. In this study, the physiological responses were evaluated for a cultivar from the State of Guerrero planted in Morelos in the same season and submitted to three coverage periods with Agribon (0, 30 and 60 days after transplanting). Also some microclimatic factors were evaluated. The results revealed a severe growth inhibition (89 to 97 % in biomass accumulation, and 75 to 88 % in leaf area) recorded in the uncovered plants as compared to the covered ones, which was accompanied by a doubling of leaf blade thickness, and by a 95 % decrease in photosynthetic rafe and a loss of 70 to 83 % in transpiration rate. The cover increased the fruit yield by 4 to 7 times as compared to unprotected plants for increasing the relative humidity and reducing the vapor pressure deficit. The limiting levels of those environmental factors are estimated in 30 % and 25 mbar, respectively, for tomato plants. The coverage for 60 days promoted a higher biomass accumulation in vegetative structures, whereas the best fruit yield was obtained with the 30-day treatment

Spanish; Castilian. El uso de cubiertas flotantes (Agribon) en jitomate (Lycopersicon esculentum Mill.) ha permitido reducir la inhibicion del crecimiento cuando es sembrado durante otono-invierno, en la region del Valle del Edo. de Morelos, Mexico. En este estudio se evaluaron las respuestas fisiologicas de una variedad criolla del Edo. de Guerrero, sembrada en dicha epoca y sometida a tres periodos de cobertura con Agribon (O, 30 y 60 dias a partir del trasplante), asi como las modificaciones microclimaticas inducidas por dicha cubierta. Los resultados revelaron que las plantas expuestas a la intemperie sufren una fuerte inhibicion del crecimiento (de 89 a 97 % en acumulacion de biomasa, y de 75 a 88 % en area foliar), acompanada de un engrosamiento al doble de la lamina foliar, y abatimientos de 95 % en la tosa fotosintetica y de 70 a 83 % en la tasa transpiratoria. Con la cubierta se incremento de 4 a 7 veces el rendimiento de fruto; la cual evita que la humedad relativa y el deficit de presion de vapor alcancen niveles restrictivos, estimados en 30 % y 25 mbar, respectivamente. La cobertura de 60 dias promovio mas el crecimiento de estructuras vegetativas, y la de 30 dias fue mejor para la produccion de fruto