A study of stomatal patterns in Plantago lanceolata L. Acer pseudoplatanus L. Sesleria caerulea L. in relation to environmental parameters

Abstract

A baseline study of leaf stomatal density, stomatal indices, guard cell length and leaf area was made in three species; a grass, Sesleria caerulea L., a herb, Plantago lanceolata L., and a tree, Acer pseudoplatanus L. in relation to environmental parameters. Chlorophyll analysis was also investigated to see if a relationship existed between density of stomata and chlorophyll content. Multivariate analysis of variance showed: significant variation of the stomatal index (SI) and stomatal density in the three species in situ in the field: generally both parameters increasing with increasing altitude but with some variation across the P. lanceolata L. sites. Leaf area was significantly reduced at higher altitudes in all species. Guard cell length significantly decreased with increasing altitude in 5. caerulea L., and A. pseudoplatanus L. but varied in P. lanceolata L. across sites. Within habitat, P. lanceolata L. appeared to show no significant difference in the SI compared to between habitat variation at both sites studied. Stomatal density was generally greater on the abaxial leaf surface of P. lanceolata L. Apart from two plant populations, no significant difference was found in the SI between the adaxial and abaxial surface. Regression analysis showed soil depth, moisture and altitude explained a considerable amount of the variation in the data. Transplants of Acer pseudoplatanus L., showed a significant increase in stomatal density and the SI with increasing altitude. Guard Cell length significantiy decreased with increasing altitude. Experimentally water-stressed plants showed variation. Sesleria caerulea L. and Plantago lanceolata L., both significantiy increased stomatal density but decreased the SI with increasing stress. The exception was in the adaxial surface of the leaves of Plantago lanceolata L. from Widdybank Fell which showed no difference in the leaf SI between treatments. Leaf area was significantly reduced except in S. caerulea L. from Widdybank Fell. The SI and stomatal density increased with increasing water stress in Acer pseudoplatanus L. Guard cell length decreased significantly in the three species under water stress. Shading of Acer pseudoplatanus L. significantiy reduced stomatal density and the SI but increased the number of stomata per leaf Leaf area and guard cell size significantly increased under shade. Total chlorophyll (chl) significantly increased with increasing altitude in S. caerulea L. and A. pseudoplatanus L. but varied in P. lanceolata L. across sites. Total Chl decreased with increasing altitude in A. pseudoplatanus L. transplants. Full grown low light leaves of A. pseudoplatanus L. had more total chlorophyll per unit fresh weight than high-light leaves but the content per unit area of leaf surface was lower in low-light leaves. Under a varied watering regime, the two species studied for chlorophyll content (A. pseudoplatanus L. and P. lanceolata L.), showed a differential response, total chl increasing slightly in A. pseudoplatanus L. but with no pattern emerging in P. lanceolata L. Conclusions drawn from this study indicate there is considerable variation both in the density and proportion of stomata produced (Stomatal index) in these three species both in the field and under manipulated environmental conditions which may have both a genetic and plastic base. This suggests care should be taken in interpreting morphological, anatomical and physiological changes in plants which may result from climatic change, in particular increased CO2 levels.