| In order to understand polyploidy and its significance in habitat differentiation and adaptation in Betula papyrifera, the morphology and leaf anatomy, water relations, gas exchange and growth characteristics of five provenances representing three ploidy levels have been compared. Morphologically, the pentaploids and hexaploids are indistinguishable. The young stems and leaves (veins) of the pentaploids and hexaploids are covered by dense pubescence, while those of the diploids are sparsely pubescent and in some case are totally glabrous. However, discontinuity of characters does not exist in Betula papyrifera var. cordifolia. The present results do not provide any support to rehabilitate it to full specific rank.;The data from this research have shown that the polyploids are more tolerant of water deficit than their diploid relatives. The polyploids have fewer stomata per unit area and smaller stomatal index than the diploids. They also have thicker upper and lower epidermis and more pubescence, which tend to reduce water loss. The polyploids have lower osmotic potential at saturation (;The polyploids differ from the related diploids in their adaptation to light intensity and temperature. The diploids undergo a greater photosynthetic reduction (44.5%) with a 4... |
