Abstract
Some 90 trifoliate leaves of various sizes were randomly selected from six 70-day old seedlings of late vegetative stage of Medicago sativa L. (fifteen leaves from each seedling) raised in Karachi (Pakistan) from seeds obtained from New Zealand. The linear measurements from the leaflets of these leaves were recorded i.e. length (LM) and width of leaflets (LB) at the broadest points on the margins. The leaves were studied for their architecture, ornamentation and leaf area estimation. The seedling shoot was pubescent. The exotic taxon was distinct from the local taxon in leaf architecture (shape and larger size of the leaflets and larger petiolar length. Leaf exhibited size-related variability in leaflet shape. Terminal leaflet of a trifoliate leaf was longer and broader than left or right lateral leaflets. Length /Width ratio averaged to 1.82 to 1.84 and didn’t vary amongst the three leaflets significantly. It appeared that the overall leaf shape as given by the aspect ratio (L /W) is generally maintained at least in mature leaves. The average area of the terminal leaflet (4.57 cm2 ) was significantly higher than that of the left or right lateral leaflets (3.98 and 3.87 cm2 , respectively). Apical angle (AA) and basal angle (BA) averaged to 82o to 84o indicating on an average acute angular placement. However, since AA and BA ranged from 68o to 100o , there were some cases of obtuse AA and BA. The value of the multiplication factors (k = leaf area measured / (LM x LB) for terminal, left and right lateral leaflets (k1, k2 and k3) in each case were non-normal, highly leptokurtic in distribution with low lateral spread. The ks values concentrated around the mean value and averaged to k1= 0.626408, k2 = 0.659049 and k3 = 0.651420. The terminal leaflet varied in area from 0.25 to 10.37 cm2 , left leaflet from 0.45 to 9.45 cm2 and right lateral from 0.22 to 9.68 cm2 . The area of a mean leaf of late vegetative stage seedlings was measured to be 12.4203 ± 0.6939 and estimated to be 12.3832 ± 0.6600 cm2 . The leaf area measured and leaf area estimated correlated highly positively with each other (r = 0.9834) and relationship between them was isometric. The average leaf area measured didn’t differ significantly with average leaf area estimated (t = 0.0389, NS). There were several types of stomata in M. sativa- anisocytic, anomocytic, and tetracytic stomata on stipule, tetracytic stomata on stem, anisocytic, staurocytic, tetracytic, and contiguous stomata on dorsal surface of leaf, and anisocytic, staurocytic, tetracytic, contiguous stomata and several stomata with common subsidiaries on ventral surface of leaf. Stomatal density on dorsal and ventral surfaces of leaves was moderate in magnitude, 100.86 ± 2.80 and 113.03 ± 5.58 per mm2 , respectively. The mean estimated total leaf area per seedling amounted to 646.33 ± 60.92 cm2 varying by 29.80 % (432.72 to 854.44 cm2 ). The estimated total leaf area per seedling (Z) related significantly with shoot length (X) and the number of leaves per seedling (Y) as given by the following equation (r = 0.9989): Z = -1.391 + 0.04182 X + 12.377 Y
