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Vegetables are a common and important source of food and nutrition but the increasing concentration of cadmium (Cd) in the food chain via wastewater-soil-vegetable continuum is posing a threat to their growth as well as human life. This study aimed at determining the effects of variation in duration of plant exposure to different dosages of Cd on growth, physiology and potential health risks of three commonly grown leafy vegetables, viz. spinach (Spinacia oleracea L.), fenugreek (Trigonella foenum-graecum L.) and coriander (Coriandrum sativum L.). The experiment was a 5 × 3 factorial containing five doses (0, 10, 20, 30 and 40 mg Cd kg −1 soil) and three (25, 50 and 75 day) durations of plant exposure. The experiment was laid out in completely randomized design (CRD) with three replications. It was found that plant height, root length, leaf area and biomass were significantly affected by increasing Cd concentration up to 40 mg kg −1 for all the vegetables. Furthermore, Cd treatments significantly affected the photosynthetic and biochemical attributes such as chlorophyll a, chlorophyll b, carotenoids and total chlorophylls at various growth stages of vegetables tested in comparison with their respective controls. Accumulation of Cd in all the leafy vegetables, its daily intake via vegetable consumption and health risk index were significantly increased with the increase in Cd concentration. The highest values of these parameters were found at 40 mg Cd kg −1 soil. It could be concluded that duration of exposure and Cd dose were very important in determining Cd toxicity, which are reflected in drastic reduction in vegetable growth and physiology. Moreover, the consumption of such vegetables would have toxic effects on human health.

Lead (Pb) is one of the most abundant heavy metal pollutants and readily absorbed by plants that exerts toxic effects and also gets entered into human food chain. There are very few examples of genetic differences being exploited to produce low Pb rice food through decreased metal uptake from Pb-polluted environment. In this regard, solution culture screening has been proposed as a rapid technique for the identification of prospective rice genotypes. In a hydroponics study, fourteen rice genotypes were tested against varying rates of applied Pb, to investigate the effects of chloride, sulfate and nitrate salts of Pb on growth, chlorophyll contents and tissue concentration of rice genotypes. The plants were exposed to 0, 100 and 200 µM Pb as PbCl 2 , PbSO 4 and Pb(NO 3 ) 2, separately for 42 days. Thus, there were seven treatments arranged in completely randomized design each with four replications. The results showed that at a certain defined Pb rate (100 or 200 µM), the toxic effects of Pb as Pb(NO 3 ) 2 to rice plants were found significantly (p ≤ 0.05) higher than PbCl 2 and PbSO 4 treatments. At all applied Pb treatments, the Shaheen Basmati and KS-282 were found tolerant to Pb because of higher growth, total chlorophyll contents, low root and shoot Pb concentration. Therefore, these both genotypes were found to be a good source for future rice breeding programs or grown by the farmers for Pb risk-free rice production in Pb polluted environment.

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To cite this paper: Shakar, M., M. Yaseen, A. Niaz, R. Mahmood, M.M. Iqbal and T. Naz, 2016. Calcium carbide-induced changes in germination, morphophenological and yield traits in cucumber (Cucumis sativus ) suppressed germination rate of cucumber seeds. Likewise, lower rates of CaC 2 were also found effective in enhancing the root and hypocotyl lengths, number of lateral roots and fresh weight of seedling while the highest rate of CaC 2 was proved inhibitory. It was recorded that the CaC 2 induced improvement in seed germination was significantly correlated (r = 0.75) with magnitude of ethylene production during imbibition. Moreover, a pot experiment was conducted under natural conditions to select optimum rate and coating material of CaC 2 regarding growth and yield parameters of cucumber. It was found that all rates of CaC 2 , irrespective of coating materials, exhibited new primary branches, early female flowering and fruit maturity. Maximum response regarding female flower count, fruit yield and ethylene emission was obtained by the application of paint coated CaC 2 at 300 mg pot -1 , which resulted in 34% more fruit yield compared to control plants.