干旱区生态环境知识资源中心

The number of seeds produced by a plant can be limited by adverse environmental factors, which can also affect the seed development originating non-viable seeds. In the I Region, Chile we have observed that Lycopersicon chilense, a tomato species endemic to Atacama Desert, has high fruit and seed production, but a low plant recruitment. We hypothesize that this could be due to two factors: (a) mother plants produce non-viable seeds because of the adverse conditions where they grow or (b) seed are viable but the environmental conditions are not suitable for seed germination. We determined the germination capacity of L. chilense seeds, subjected to different temperatures and mannitol and NaCl concentration, from motherplants growing with plenty water supply (+H2O) and other groups growing with water deficit (-H2O). Water supply affected the number of seeds germinated and the time needed by the seeds to germinate under different temperatures and water potential. Seeds from H2O plants were able to germinate at lower water potentials and in shorter time than seeds from +H2O plants in the case of mannitol. The contrary occurred with NaCl, in which a higher seed germination and shorter time for germination occurred in seeds coming from +H2O plants. Seed germination of L chilense progressively decrease at water potentials lower than -0,5 MPal being this decrease more evident with NaCl; in both cases there was a germination delay. The optimum temperature for seed germination was between 15 and 25 degreesC. Seeds of L. chilense did not germinate at temperatures lower than 8 degreesC or higher than 35 degreesC. Data show that although L chilense plants produce viable seeds under the various water conditions studied, the capacity of seeds to germinate is limited to a narrow range of environmental conditions. Some hypotheses are advanced to explain the presence of this species in desert environments.