WATER RELATIONS OF 2 TOMATO SPECIES UNDER WATER-STRESS AND RECOVERY

Tomato plants of domesticated (Lycopersicon esculentum (L.) Mill. cv P-73) and wild relative (L. pennellii (Correll) D'Arcy accession PE-47) species growing in a growth chamber were subjected to drought by withholding irrigation for 7 days, After that, plants were re-irrigated and the recovery was seen after 13 days. Control plants were daily irrigated at 50% field capacity. Water stress affected the development of L. pennellii to a lesser extent, whereas L. esculentum showed a decrease in leaf area and succulence and symptoms of wilting. Minimum leaf water potentials (psi(1)) observed were -1.8 and -1.4 MPa for L. esculentum and L. pennellii, respectively. Leaf conductance (g(1)) decreased in response to water stress in both species. Recovery of psi(1), in L. pennellii was rapid, whereas that of g(1) lasted 6 days. In L. esculentum g(1) started to increase just after plants were reirrigated, which indicated that a hydroactive mechanism controls the stomatal aperture. An osmotic adjustment of 0.13 MPa was observed only in L. esculentum, based on the accumulation of reducing sugars and proline. This indicates a glycophytic response involving high energy costs, The higher resistance to water stress by L. pennellii can be explained by more efficient stomatal control, which resulted in a lower leaf water deficit and the absence of morphological changes.