Variation in net photosynthesis, stomatal characteristics, leaf area and whole-plant phytomass production among ten provenances of neem (Azadirachta indica)

Abstract

Variation in net photosynthesis, CO2 exchange parameters, stomatal characteristics, leaf area and seedling dry weight were investigated among 10 provenances of neem (Azadirachta indica A. Juss.). Significant provenance variation was established for net photosynthesis (8.14 to 15.13 μmol m-2 s-1), stomatal conductance (0.37 to 0.59 mol m-2 s-1), stomatal density (145 to 204 mm-2), and total guard cell length (2681 to 3873 μm). Net photosynthesis was positively correlated with whole-plant dry weight and leaf area. Stomatal density was positively correlated with net photosynthesis, whole-plant dry weight, and leaf area. Total guard cell length was positively correlated with all of these traits. Information on six traits was used in a cluster analysis to construct a dendrogram to assess phenetic relationships among the provenances. With a few exceptions, the dendrogram revealed three major clusters grouped according to rainfall distribution. The study indicated that whole-plant phytomass production of neem seedlings was associated with photosynthesis and stomatal characteristics during the early stages of growth.