Ecophysiological differences related to photosynthesis were compared in holm oak Quercus ilex leaves from undisturbed holm-oak vegetation, resprouts after fire and resprouts after tree-fell. No significant differences in any parameter measured were observed between the two kinds of resprout throughout the first growing season following disturbance. Resprouting leaves showed lower carbon isotope discrimination (Δ) and intercellular CO concentration (p ), and higher photosynthesis, leaf conductance and transpiration rates than leaves from undisturbed stands. Nitrogen, soluble protein content and ribulose bisphosphate carboxylase (RuBPCase) activity were 88%, 96% and 45% higher respectively, in both kinds of resprout. The results indicate that photosynthetic capacity, rather than stomatal conductance, is the limiting factor in photosynthesis in resprouts, Chlorophyll content and chlorophyll a/b ratio did not differ between resprouts and undisturbed leaves, indicating that the observed differences were not a result of differences in light environment during leaf development. Leaf mass per area (LMA), was 80% higher in the resprouts, and was negatively related (r=-0.86) to Δ and positively related (r=0.87) to N content. Enhanced carbon assimilation after disturbances resulted in higher water use efficiency, as indicated by lower Δ values in the resprouts. We conclude that the cause of defoliation was not relevant in the physiology of the resprouts, suggesting the importance of underground organs.
The effect of different concentrations of lead was investigated in two different ways in the leaves of Helianthus annuus plants. In the first way, removed leaf discs from 5-wceks old plants were floated in 0.05, 0.25, 2.50 and 5.00 mM PbNO3 solutions for 2, 4 and 6 days. In addition, the chlorophyll content and the activity of peroxidase enzyme which are the parameters of stress conditions in plants were also measured. In this experimental series, a decrease was determined in polyamine and chlorophyll contents and in the peroxidase activity in leaf discs which were treated with different concentrations of lead. In the second experimental series, one half of the upper leaves of 5-wceks old plants were used for lead treatments, while the other half for control. In half leaf experiments, lead in 0.05, 1.25 and 5.00 mM concentrations were sprayed to the both sides of the half leaves. According to the results of the half leaf experiments, 0.05, 1.25 and 5.00 mM lead treatments increased the putrescine content in 27, 15 and 9 % respectively. On the other hand, chlorophyll content and the activity of peroxidnse enzyme were decreased with the treatments of lead.
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