Abstract
This paper describes the seedling morphology of Albizia lebbeck (L.) Benth. including stomatal characteristics. Seedlings of A. lebbeck are epigeal, phanerocotylar type with reserve type cotyledon - exhibiting quite faster growth rate and nyctanastic movement. The cotyledons are opposite ovate, green and thick and food-laden. They are concave inside and convex outside. The area per cotyledon averaged to 162.83 ± 1.47 mm2 and cotyledonary area per 5-day old seedling averaged to 325.67 ± 4.26 mm2 . They are sessile and provided basally with a groove to accommodate stem with which they form an angle of 45o . There arise some seven veins from the arch in the basal region of the cotyledons. They traverse lengthwise – apparently brachidodromous. Primary leaves were unipinnate and subsequent leaves were bipinnate. Primary leaves had no petiolar or acropetiolar glands. Glands associated with bipinnate leaves only – acropetiolar glands were generally more prevalent. In bipinnate leaves, at least one basal leaflet in each rachii was rudimentary. The leaf area per 25-day old seedling averaged to 204.4 ± 8.24 cm2 varying from 177.9 to 243.4 cm2 . Foliar epidermal cells on dorsal surface are irregular or polygonal in shape and their anticlinal walls were straight in cotyledons and arcuate with some degree of waviness in leaf particularly on the ventral surface. In seedlings the epidermal cells were papillose. In mature tree leaflet the epidermal cells were convex papillose (both flat-topped and conical types with tendency of cuticle deposition on top of cells and then descending along the wall. Delicate non-glandular blunt-apex trichomes were observed on petiole, basal part of rachii and margins of stipules and leaflet. Hypocotylar stomata were of anomocytic type. On cotyledon, paracytic, anisocytic and staurocytic and anomocytic stomata were present. In young leaflet (2.0 x 0.6 cm in size), the stomata were found to be paracytic (c. 85%), anisocytic (c. 14%) and very few tetracytic types on dorsal surface. On ventral surface, paracytic stomata were predominantly abundant with some anisocytic types also. Stomata on dorsal surface of leaflet were quite infrequent and stomatal density averaged to 3.77 ± 0.78 stomata per mm2 (0-19.96 per mm2 ). Stomata on ventral surface of seedling leaflet averaged to 156.96 ± 5.266 stomata per mm2 varying around 25. 99%. There were no stomata on dorsal surface of leaflet of parent tree and on ventral surface stomatal density averaged to 164.23 ± 9.612 stomata per mm2 . The basic type of stomata in A. lebbeck appears to be paracytic ones and other types as secondarilyderived through development of cell wall (s) in subsidiary cell. Stomatal aberrations were observed in A. lebbeck generally with respect to the stomatal cell. Stomata without guard cells differentiation (arrested development of guard cells) were observed on both surfaces of cotyledons and leaflets of seedling as well as on mature leaflet from the parent tree presumably as a result of genotoxic effects of very high transport density. Cuticular wax crystalloids were composed of irregular platelets (rosettes of platelets, Faballes type). The number of platelets per rosette varied considerably and appeared to fuse with each other forming lumps.
