Leaf angle change and anatomical structure of Populus deltoides, P. cathayana and their hybrid F1

ObjectiveTo provide evidences for selecting appropriate poplar clones for southern mountain area in China, the responses to sunlight and adaptability to habitat for Populus deltoides cv. 'I-69'(♀)(F), P. cathayana (♂) (M) and 3 types of hybrid F1, including female-parent-like (FP), intermediate (I) and male-parent-like (MP), were compared and analyzed.

MethodThe diurnal changing pattern of twist angles and midrib angles and leaf morphological indexes were measured, and anatomical structures of leaves and petioles were observed by scanning electron microscope.

ResultThe co-operation of changing in twist angles and midrib angle led to leaf movement for maternal F, while the movement of midrib angles was mainly forced for paternal M. The response to sunlight by changing the leaf orientation for 3 types of F1 was not significant. Obvious differences in anatomical structure were found in parental poplars and F1 types. As the types of isobilateral leaf, F and FP possessed the ratio of 0.87 and 1.02 for stoma density on the upper to the lower of leaf epidermis, no sponge tissue was observed, and 2 layers of palisade tissue, located in the upper and lower of leaf, occupied more than 0.7 of total thickness of leaf. As the types of bifacial leaf, including F, I and FP, the ratios of stoma density on the upper to the lower of leaf epidermis were 0.08, 0.45 and 0.55, respectively; thicker sponge tissue and palisade tissue on the upper leaf were observed, and the rank of the ratio of palisade tissue to sponge tissue was MP(0.75)>I(0.55)>M(0.47). Anatomical structure of F petiole showed the tendency of cross-section shape varying from narrow-oval to wide-heart-shape, with a gradually changing arrangement of vascular bundle from vertical to horizontal along the upper to lower section of petiole. While the structure of M petiole showed small variation, from near round to heart-shape in shape, and radial pattern in arrangement of vascular bundle from the upper to lower section.However, for 3 types of F1, both the shape and arrangement of vascular bundle intervened two parents.

ConclusionThe results provide possible appropriate poplar clones for South China: I and MP type of F1 are nominated for mountainous area of high altitude; meanwhile, FP may adapt to mountainous area of low altitude.