Chromium Toxicity on Seed Germination, Root Elongation and Coleoptile Growth of Pigeon Pea (cajanus Cajan)

A lab experiment was conducted to evaluate the effect of chromium (Cr) on seed germination, root elongation and coleoptile growth in pigeon pea (Cajanus cajan). The seed of the pigeon pea was treated with five concentrations of Cr (0, 20, 40, 80 and 100 ppm). The results indicated that the per cent germination of test crop was decreased after application of 20 ppm Cr concentration. The effect on root elongation and shoot growth was more pronounced which gradully decreased with increasing levels of chromium application from 20 to 100 ppm. With the time, root elongation and coleoptile growth was decreased during crop growth. The root elongation of the pigeon pea was more sensitive than coleoptile growth for Cr toxicity. Key word: Chromium, Coleoptile growth, Germination, Pigeon pea, Root elongation. *Corresponding author’s e-mail: [email protected] Pigeon pea is an important legume crop of the semiarid tropics. It is cultivated in more than 25 tropical and subtropical countries, either as a sole crop or intermixed with cereals. Being a legume, it enriches soil through symbiotic nitrogen fixation. It contains amino acid like methionine, lysine, tryptophan, and plays an important role in reducing malnutrition for millions of people around the world (Bressani et al., 1986). Increasing population directly enhancing the demand of healthy food for hungry mouth, on limited natural resources and land. Use of effluent water as irrigation in pulse growing areas, reducesing the crop quality as well as crop yield. The tannery wastes (effluents and sludge) contain high concentrations of chromium (Cr). The indiscriminate disposal of these wastes resulted in severe pollution of soil and water in the cities like Kanpur and Vellore, where most of the tanneries exists. Pollution of soil and water drastically reduced the crop yield upto 40% over the years and the total cropped area decreased significantly (Nath et al., 2005). The experiment was conducted at Indian Institute of Soil Science, Bhopal in the year 2013 with four levels of Cr (20, 40, 80, 100 ppm) along with control in three replication. The effect of Cr were studied on pigeon pea variety ICPL 87119. The germination per cent was recorded after 72 hour (h). The root elongation and coleoptile growth of germinated seeds were measured at 72, 120,168 and 240 h under each treatment. Statistical analysis was performed in complete randomized design (Gomez and Gomez, 1983). Chromium effect on germination: The maximum germination (100%) was recorded in control and 20 ppm chromium levels (Table 1). With increasing levels of chromium after 20 ppm decreased the germination by 4, 5, 7% in 40, 80, and 100 ppm Cr levels, respectively at 72 h. This response of low levels of germination upon Cr exposure can be attributed to decrease in  and  amylase activities under Cr stress (Zeid, 2001). The amylase hydrolysis of starch is essential for sugar supply to developing embryos. Decrease in amylase activity under Cr treatment decreases sugar availability to developing embryo which may lead to the inhibition of seed germination (Dey et al., 2009). Chromium effect on root elongation: Increasing the Cr level decreased the root elongation, with highest reduction in 100 ppm and lowest in control (Table 1). the Cr level 100 ppm affected more root elongation at all time intervals compared to control followed by 80, 40 and 20 ppm. DOI: 10.5958/j.0976-0571.37.2.034 228 LEGUME RESEARCHAn International Journal TABLE 1: Effect of chromium toxicity on germination, root elongation and coleoptile growth of pigeon pea. Chromium level (ppm) Germination (%) Root elongation (cm) Mean Coleoptile growth(cm) Mean 72h 120h 168h 240h 72h 120h 168h 240h 0 100 36.7 91.3 106.3 136.7 92.8 53.7 73.6 100.6 116.8 86.2 20 100 32.0 63.5 68.8 83.3 61.9 45.8 65.7 73.7 80.5 66.4 40 96 22.7 35.0 41.3 43.8 35.7 28.6 48.5 59.0 60.4 49.1 80 95 15.6 33.6 37.3 42.0 32.2 26.0 46.1 55.0 58.3 46.4 100 93 8.3 23.7 35.2 41.3 27.1 21.3 41.3 53.0 53.3 42.2 LSD(p= 0.05) 2.44 6.4 19.2 51.3 43.7 15.2 15.2 29.6 10.7 However, significant difference was not observed between 80 and 100 ppm Cr level at all time period except 72 h. Increasing the crop growth period root elongation increased with positive increment upto 168 h in all the Cr levels, but after that it increased with diminishing increament. Many researcher showed that 5 mg L-1 of Cr (VI) increased root growth comparatively for the control, and at higher doses (20 and 40 mg L-1) there was a dose-inhibition effect. Decrease in root growth due to presence of Cr(VI) can be explained by inhibition of root cell division and/or elongation, which might have occurred as a result of tissue collapse and consequent incapacity of the roots to absorb water and nutrients from the medium (Oliveira, 2012) combined with extension of cell cycle (Sundaramoorthy et al., 2010). Chromium effect on coleoptile growth: The coleoptile growth of the pigeon pea was also affected by chromium levels, but it was less affected than root elongation (Table 1). Coleoptile growth was significantly affected by 20, 40, 80 and 100 ppm Cr levels over control.With increasing Cr levels, mean coleoptile growth reduction maximum (42.2 cm) in 100 ppm level where as minimum (86.2 cm) was observed in control. But there was no significant difference among 40, 80 and 100 ppm Cr levels. The crop growth period has significant effect on the coleoptile growth and it was incresed up to 168 h after that it increased with diminishing increment. Higher concentration of chromium affected root growth of wheat as well as oat crop (Opez-Luna, 2009), which results in reduced coleoptile growth. Chromium application of 2, 10 and 25 ppm through nutrient solution reduced plant height by 11, 22 and 41% respectively in oat (Anderson et al., 1972). The decrease in plant height could be due to the reduced root growth and consequent decrease of nutrients and water transport to the higher parts of the plant. Moreover, Cr transport of the aerial part of the plant can directly impact cellular metabolism of shoots contributing to the reduction in plant height (Rout et al., 1997). Increasing population require quantities as well as quality of food. Pulses are the cheap source of protein in developing nations, in which pigeon pea is contributing a significant role in the tropical and subtropical regions. Use of effluents as irrigation containing Cr has drastic effect on germination, root elongation and coleoptile growth. 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