Coexistent Heteroblastic Needles of Adult Pinus canariensis C.Sm. ex DC. in Buch Trees Differ Structurally and Physiologically

Great variation in shape and size between primary (juvenile) secondary (adult) needles, so-called leaf-heteroblasty, occurs several Pinus species. Most of them loss needles during the juvenile-to-adult transition tree. An exception to this is canariensis (a Canary Islands endemism) which basal resprouting twigs adult trees frequently wear both needles. Taking advantage extraordinary study-case-species, we conducted an exhaustive comparison needle types through quantitative analyses anatomy, photochemical performance, gas exchange, resistance extreme dehydration temperature. We hypothesized that would show lower investment leaf structure but higher photosynthetical efficiency. Primary had less stomatal density thicker wettable cuticles. In cross section, showed smaller structural fraction (e.g., percent hypodermis, endodermis vascular tissue) photosynthetic parenchyma. Significant differences were not found net carbon assimilation their mass area values. Interestingly, electron transport rate, they additionally much more efficient retaining water under severe controlled desiccant conditions. When subjected temperatures (?10° +50 °C), recovered better efficiency than after +46° +48 °C heat-shock treatments. Our results indicate broaden diversity physiological responses against environmental constrains P. trees. Considering a fire-resistant species, could be particularly useful drastic change such fire or gap opening forest.