Morphological and anatomical variations ofCajanus cajan (Linn.) huth raised in cadmium-rich soil

Abstract

Different concentrations of cadmium in the growing media affected morphological parameters of Cajanus cajan. Over time, the amount of increase in shoot and root lengths, number of branches and leaves per plant, single and total leaf areas, and dry mass of leaves, was significantly lower for treated plants compared with controls. The root-shoot length ratio, which varied little over time, was relatively low for the treated plants. Although dry mass of both stems and roots increased, the rates were considerably low under Cd stress. The root-shoot dry mass ratio in the controls was highest during flowering and lowest in the post-flowering stage, but continually declined over time for the stressed plants. Compared with the controls, treated plants had fewer pods, with the number decreasing as the Cd concentration increased. Cd content was greater in roots than in stems or leaves, and leaves had greater amounts than did stems at higher doses. For all plants, the width and density of vessel elements and the length of fibers in the wood of stems and roots increased with plant age. However, the rate of increase was generally lower in the treated plants, the difference being more pronounced with higher doses of Cd. This indicated a reduced ascent of sap and, hence, less available water for tissues in treated plants.

Morpho-anatomical responses ofTrigonella foenum graecum Linn. to induced cadmium and lead stress

“…However, reduction did not vary significantly at different stages of development. Such results have been reported by Puckett et al (1977) and Khudsar et al (2000). Density of stomata in the presently investigated species also declined under heavy metal stress.…”

“…Bharadwaj and Mascarenhas (1989) also observed marked leaf area reduction with increase i1 concentration of the heavy metal in the medium. Besides leaf area, significant decrease was observed in the number of leaves, single leaf area and total leaf area of the presently investigated species at all its developmental stages, which draws support from similaJ observa- (Khudsar et al, 2000). Present investigations also revealed significant reduction in stomatal length and width under induced metal stress (Tables 4-7).…”

“…Vessel element length and width decreased significantly and consistently in the stem and root of the metal treated samples of Trigonella. Development of short vessels in plants growing under stressed conditions has also been reported in Polygonum glabrum (Khan et al, 1984), Calotropis gigentia (Iqbal et al, 1986b), Euphorbia hirta (Usmani, 1990), Lagerstroemia reginae, and Alstonia scholaris (Jabeen and Abraham, 1998), and Peristrophe and Ruellia (Nighat, 1998;Khudsar et al, 2000). Such variations can have severe physiological and metabolic implications for the plants as Lamoreaux and Chaney (1977) reported reduced relative water conductivity in excised stem sections of Cd-treated silver maple.…”

“…Density of stomata in the presently investigated species also declined under heavy metal stress. Such response has been suggested to be a common mechanism adopted by the plants to cope with the pollution load (Khudsar et al, 2000). Reduction in leaf size in the treated plants, as discussed earlier, indicates not only retarded growth but also results in reduction in green surface area and thereby accommodation of lesser number of stomata.…”

“…Populus tremuloides and Betula pendula, may also alter wood structure (Eckstein et al, 1981;Kozlowski and Constantinidou, 1986). On the contrary, increase in the area occupied by vasculature under the stress of environmental pollution has also been reported and has been regarded as an adaptive response to ensure the maintenance of water uptake particularly during the flowering and fruiting stages of Sida spinosa (Mahmooduzzafar et al, 1986), C/eome viscosa (Ahmad et al, 1987), Lantana camara, C. tora, C. occidentalis (Iqbal et al, 1987a, b), Am~ranthus viridis, Euphorbia hirta (Usmani, 1990), and C cajan (Khudsar et al, 2000).…”