The daily and seasonal course of the gas exchanges, leaf temperature and water potential of Barbados cherry (Malpighia emarginata D.C.) were evaluated under field conditions. The experiment was carried out in Paudalho, Pernambuco State, Brazil. Measurements of photosynthetic capacity in the wet season were also made. Changes in daily and seasonal behavior of gas exchange, water potential, and leaf temperature were observed. The transpiration and water potential measurements were higher at the beginning of the morning and at the end of the afternoon, while those for diffusive resistance and leaf temperature were lower at these same periods of the day. There was a reduction of gas exchange with the environment as a result of the lower transpiration during the hotter hours of the day, being this tendency strongest in the dry season and in the UFRPE 7 accession. The lowest values for leaf water potential were registered in the dry season, varying from -3.37 MPa (UFRPE 7) to -4.32 MPa (UFRPE 8), while the maximum resistance values varied from 16.30 cm s-1 (UFRPE 7) to 22.10 cm s-1 (UFRPE 8) during this same season. The water potential and the diffusive resistance showed a strong correlation to the vapour pressure deficit. The greatest photosynthetic capacity was registered for mature leaves in the UFRPE 8 plant. The physiological expressions displayed showed that the plants are resistant to drought and these expressions appear to help the plants resist to periods of water stress when they appear. The UFRPE 8 accession is more adapted to dry period than UFRPE 7.
Malpighia emarginata; plant water relations; leaves; photosynthesis; transpiration; temperature resistance; water stress
