干旱区生态环境知识资源中心

Pine needles reflect some of the most outstanding xeromorphic characteristics of sclerophyllous plants. Detailed descriptive studies about their anatomy and morphology were carried out since the beginning of the past century but the role the different tissues play in adaptation to diverse environments is still little known. In this work we analyzed morphological and anatomical needle traits of seventeen natural populations of Pinus canariensis Chr. Sm. Ex DC to identify adaptive traits related to drought resistance and determine their variability throughout a wide range of ecological conditions. A Principal Component Analysis revealed two groups of traits, one related to drought adaptation: maximizing gas exchange, avoiding water loss and storing water and the other to photosynthesis. Results support a predominantly mechanical function of hypodermis and a possible role of transfusion tissue to withstand dry conditions, thanks to its water storing capacity. The inversion of the patterns of the relative area of the dermal and transfusion tissues in the xeric region was justified due to the influence of the extreme dry Saharan wind from the East. A clear adaptation of Pinus canariensis needles to contrasted environments is evidenced suggesting distinct phenotypic needle features in the most xeric stands.