In this study it has been shown that increased diffusional resistances caused by salt stress may be fully overcome by exposing attached leaves to very low [ 06), that would implicate a reduced rate of RuBP regeneration, and, thus, a metabolic impairment. However, the analysis of the A -C i curves made on pre-conditioned leaves, showed that the estimates of the photosynthetic capacity parameters were much higher than in the standard A -C i responses. Moreover, these values were similar in magnitude to the average values reported by Wullschleger ( Journal of Experimental Botany 44, 907-920, 1993) in a survey of 109 C 3 species. These findings clearly indicates that: (1) salt stress did affect g s and g m but not the biochemical capacity to assimilate CO 2 and therefore, in these conditions, the sum of the diffusional resistances set the limit to photosynthesis rates; (2) there was a linear relationship ( r 2 = = = = 0.68) between g m and g s , and, thus, changes of g m can be as fast as those of g s ; (3) the estimates of photosynthetic capacity based on A -C i curves made without removing diffusional limitations are artificially low and lead to incorrect interpretations of the actual limitations of photosynthesis; and (4) the analysis of the photosynthetic properties in terms of stomatal and non-stomatal limitations should be replaced by the analysis of diffusional and non-diffusional limitations of photosynthesis. Finally, the C 3 photosynthesis model parameterization using in vitro -measured and in vivomeasured kinetics parameters was compared. Applying the in vivo -measured Rubisco kinetics parameters resulted in a better parameterization of the photosynthesis model.

The salt tolerance of two greenhouse bell-pepper hybrids (Capsicum annuum L.,`Sonar' and Lamuyo') was studied during germination, seedling growth and vegetative growth in hydroponic culture. Salinity treatments were imposed by irrigating with half-strength Hoagland solution containing 0, 10, 25, 50, 100 and 150 mM/l of NaCl. Salinities up to 50 mM delayed germination but did not reduce the ®nal germination percentage. It was reduced signi®cantly at 100 and 150 mM NaCl in both hybrids. Seedling growth was reduced signi®cantly with salinities higher than 10 mM NaCl. Plant growth parameters such as plant height, total leaf area and dry weight were signi®cantly (P0.05) reduced at salinities higher than 25 mM NaCl in both hybrids. Roots had the highest Na concentration compared to leaves, which increased with increasing salinity, while Cl À in leaves was much higher than Na . Potassium concentration of plant tissues was less affected than Na and Cl by salinity increase. Total fruit yield in both hybrids was signi®cantly reduced at salinities higher than 10 mM NaCl, the reduction being 95% at 150 mM NaCl. Both, fruit number per plant and fruit weight were reduced by the salinity. Our results suggest that during the growth stages studied, the hybrid`Lamuyo' is more sensitive to salinity than the hybrid`Sonar'.

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