Plant-size data and estimation of some vital leaf characteristics in naturally growing Nicotiana plumbaginifolia viv. (Solanaceae) in Karachi

Nicotiana plumbaginifolia Viv. (Tex-Mex tobacco) is recorded from Karachi as a rare winter weed in flower beds and growing as road-side plant near plant-nurseries and along sewerage lines. Data on its plant size and the leaf characteristics, based on sample size of 120 leaves, are presented here. Measured Leaf area of radical leaves varied from 24.44 to 126.03 cm2 (mean 80.8 plus minus 5.86 cm2; CV = 34.04%) and for cauline leaves from 0.61 to 124.36 cm2 (mean: 22.29 cm2; CV = 126.38%). The regression coefficients were computed from multiple regression to fit in the allometric model - Y = a + b1X1 + b2 X2, where Y was the true leaf area (LA) and X1 and X2 were leaf length and leaf breadth, respectively. The predictive equation was as follows: Log e LA = - 0.38295 + 0.88962 Log e L + 1.06053 Log e B plus minus 0.098195, t = -5.72 t = 17.97 t=29.04, p less than 0.00001 p less than 0.00001 p less than 0.00001, R2= 0.9953; Adj. R2 = 0.9952; F = 12241.7; r = 0.9976, OR LA = 0.68185 (L 0.88962. B1.06053). Also, the value of the multiplication factor K for each leaf was found by employing the formula, K = LA / (L*W) and employing average K value, 0.58206, the leaf area for each leaf was computed as Leaf area computed = K*L*W. By comparing the estimated leaf area with measured leaf area it was found that allometric estimation was little better than k factor analysis in the present case. Leaf Dry matter of individual leaves (LDM) behaved more or less in the same manner as LA. Average multiplication factor KLDM was arrived at 0.00267619. The estimated LDM using formula, LDM = KLDM *L*B, was not statistically different from the measured LDM (X2 = 4.40, df = 118; NS). The Estimated LDM related closely with measured LDM. (r = 0.9312; df = 118; p less than 0.00001). Specific Leaf Area (SLA) was expressed as one-sided graphically determined leaf area of a fresh leaf divided by its oven-dry mass (cm2/ per g) and the inverse of SLA was referred to as Specific leaf mass (SLM). SLA varied substantially from 63.5 to 576.83 (CV= 36.58%) amongst the leaves investigated. The curvilinear or logarithmic relationship of SLA with LA appeared to be little better than simple linear relationship between them. In short, smaller are the leaves, lower the SLA. Larger are the leaves, larger the SLA. SLA of cauline leaves was consistently lower than that of radical leaves in all individual plants examined. Considering overall variation in SLA in the two types of leaves, SLA was comparatively of higher order in rosette leaves (354.09 plus minus 21.39; N = 22, CV= 28.3%) than cauline leaves (231.59 plus minus 7.58 cm2/ per g; N = 98, CV= 32.4%). High SLA of rosette leaves may be a significant factor enabling early ground cover by basal leaves for light interception in this species. The Leaf to leaf analysis of SLA in leaves on the main stem and the lateral branches in two individual plants showed almost a regular trend of increase of SLA from apex to the base of the plants. Apical leaves had lower SLA than subsequent basal leaves. Exposure of axial leaves to comparatively more irradiance may probably the reason for low SLA of axial leaves. SLA related with ratio of Leaf Dry Mass contents (LDMC) negatively. Specific Leaf Mass (SLM), an inverse of SLA, varied more in cauline (42.8%) than in radical leaves (25.8%). The values of SLM for cauline leaves were, however, generally higher (mean = 0.004901 plus minus 0.0002; range: 0.00241 to 0.01574) than for radical leaves (mean = 0.00303 plus minus 0.00166; range: 0.00173 to 0.00432). Since there appears no significant difference in hydrators between radical and cauline leaves, differences in SLM, in them appears to be attributable to environmental differences. Possibly exposure of axial leaves to more irradiance and consequently their mtire active photosynthetic role is the reason for their high SLM.