EFFECTS OF TEMPERATURE ON GROWTH, DRY-MATTER PRODUCTION AND CO2 ASSIMILATION IN CHERIMOYA (ANNONA-CHERIMOLA MILL.) AND SUGAR APPLE (ANNONA-SQUAMOSA L.) SEEDLINGS

This study compares the growth and physiological response of cherimoya and sugar apple seedlings in order to examine their adaptability to 2 0/15 degrees C and 30/25 degrees C day/night temperatures in sunlit gl ass-house conditions. Shoot growth was higher at 30/25 degrees C than at 20/15 degrees C in both species. In sugar apple, temperature had ob viously positive effects on shoot growth: the shoot grew vigorously at 30/25 degrees C, but slowly at 20/15 degrees C. In cherimoya, tempera ture effects were relatively small: differences in growth response at the two temperature regimes were smaller than those in sugar apple. St arch content in sugar apple was also higher at 30/25 degrees C, wherea s that in stem and root of cherimoya was higher at 20/15 degrees C. Ca rbon dioxide assimilation rate (A(CO2)) of the two species was higher at 30/25 degrees C than at 20/15 degrees C under low irradiance. In ch erimoya, A(CO2) decreased drastically when leaves were exposed to high irradiance at 30/25 degrees C. High temperature and irradiance increa sed leaf temperature to above 35 degrees C. With increased leaf temper ature, leaf vapor pressure deficit rose and stomatal conductance decli ned, This acclimation was associated with the reduction of photosynthe sis in cherimoya. Sugar apple had higher photosynthetic activity at 30 /25 degrees C, which reflected in vigorous shoot growth. Relatively co nstant leaf temperature in sugar apple seemed to facilitate the high r ate of A(CO2) in warm conditions. The results of this study indicate t hat temperature affected shoot growth and photosynthesis by influencin g stomatal conductance via leaf vapor pressure deficit in cherimoya. ( C) 1998 Elsevier Science B.V.