Abstract
The leaves of Carissa macrocarpa (Eckl.) A. DC., collected from plants grown as hedge at Oud Metha, Dubai, were studied for their phenotypic traits, morphometric characteristics, leaf area estimation and surface micromorphological structure. Short phytography of the plant has been described. Leaves were variable in shape - ovate, oblong, orbicular or almost round. Leaf length (measured from umbo region to the apex) averaged to 4.18 ± 0.12 cm with a moderate degree of variation (1.4 -7.5 cm, CV: 28.73%). The leaf width at the widest points on the margins averaged to 3.12 ± 0.098 cm varying around 31.33% (1.0 - 6.2 cm). Around 92% of the leaves showed leaf length ranging between 2.1 and 6.0 cm. Aspect ratio (Length / breadth) of leaves in C. macrocarpa, averaged to 1.373 ± 0.0268 (varying from 0.87 to 2.36 with moderate variation of 19.21%. Apex angle averaged to 97.04 ± 1.387o varying around 14.3 %. It was lesser than 90o in 25% of the leaves, 90o in 11% of the leaves and greater than 90o in 64% of the leaves (91 – 148o ). Leaf base angle averaged to 109.44 ± 1.095o . It was ≤ 90o in 5% leaves and larger than 90o (91 – 143o ) in 95% of the leaves i.e., in most of the cases leaf base was obtuse. Base angle related with apex angle as, Base Angle = 55.234 + 0.559 Apex angle ± 7.780. Leaf base in umbo area embayed in sinus in some cases and gave rise to cordate type of leaf base otherwise cuneate. Apical leaf extension length (La; distance on a perpendicular from the distal most point of mid-vein to the distal most extension of the leaf tissue) averaged to 1.33 ± 0.118 (N = 9, 1.0-1.5mm) as found in only in nine leaves. La was zero (non-existent) in 91% of the leaves. Basal leaf extension length (Lb) was observed in 14 leaves only which had cordate leaf base and their umbo region embayed in sinus. Lb was zero (nonexistent) in 86% of leaves. Lb averaged to 1.714 ± 0.276mm (N = 14, 0.5 – 4mm). Spines were bifurcate oppositely produced on node and quite variable in size - small to giant (c 10 cm). The value of mean arithmetic coefficient (k) for leaf area estimation was found to be 0.70980 ± 0.008128 varying from 0.51 to 1.0529 (CV: 11.45%) and concentrated around the mean value. Leaf area (LAM, cm 2 ) was found to relate to the multiplicative parameter, LL (cm) x LB (cm), as given by the equation: (LAM ) = 0.702.(LL x LB) 1.002 ± 0.115, R2 = 0.968). Leaf area per leaf, in a sample of 100 leaves, averaged to 9.884 ± 0.5427 cm2 varying from 1.02 to 27.98 cm2 (CV: 55.93. It was positively skewed and leptokurtic – asymmetrically distributed. In 85% of the leaves LAM varied from 12.6 to 15.0 cm2 . Under the given growth conditions, Leaf dry matter, in comparison to SLA, appeared to be a better parameter in C. macrocarpa. The leaves of C. macrocarpa were hypostomatic. Lower epidermis had stomata generally of anomocytic type but also anisocytic type of arrangement of subsidiaries was seen. Stomata were round or oval or wide elliptical measuring stomatal diameter c 33.5 -35.0 µm and outer stomatal ledge aperture c. 15 µm. They were variable in size and orientation. Stomata with common subsidiary (ies) were present. Anticlinal walls of pavement epidermal cells were straight to curvy. Leaves were trichomatous when young. In a sample of 60 microscopic frames of vision, the stomtal density per mm 2 on the ventral surface of leaves averaged to 283.8 ± 5.41 stomata varying from 190.35 to 432.62, CV: 14.77%. Leaf cuticle appeared to be in form of sheet. There were, however, epicuticular crystalloids, probably waxy, in form of granules and platelets which appeared to fuse to form lumps of various shapes.
