Effect of Arsenic on Photosynthesis, Growth and its Accumulation in the Tissues of Allium cepa (Onion)

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Arsenic is a well known carcinogenic element, that can harm not only human health but, plant and bacteria as well. Replicated experiments confirmed that, Arsenic accumulates in the different tissues in different parts of the plant and, adversely affects the growth and productivity of the plants. It is a threat for millions of population in terms of health and food security both. Therefore, a pot experiment was designed and conducted to investigate the effect of arsenic on photosynthetic pigments, Chlorophyll-a and –b, growth behavior, and its accumulation in the tissues of different parts of onion plants (Allium cepa). Test plants were subjected to pot experiment under natural conditions. Four pots were prepared to grow onion plants, irrigated with equal volume of different Arsenic solution (NaAs3), 0.00 mg/l, 0.200mg/l, 0.600mg/l, and 0.800mg/l concentration with one pot for control respectively, throughout the experiments. Both chlorophyll-a and -b contents in onion leaf increased significantly with the increase of water arsenic concentrations. The highest chlorophyll-a (0.004847/g) and chlorophyll-b (0.006528/g) contents were estimated in the onion leaf irrigated with 0.800mg/l of Arsenic whereas, in control plant it was lowest (chl-a 0.002363/ and chl-b 0.004092/g). A high positive correlation was observed between water arsenic (R2= 0.897 and 0.963) & soil arsenic (R2= 0.926 and 0.919) with chlorophyll-a and chlorophyll-b respectively. High positive correlation was also observed even for onion growth verses soil arsenic and water arsenic (R2=0.994 and 0.968) and water Arsenic with leaf biomass (R2=0.973) respectively. However, no Arsenic accumulation was detected in the tissues of different parts of the onion plants suggesting that, arsenic (NaAs3) influenced the 40 K. Singh Sushant and A.K. Ghosh biochemistry of photosynthesis which ultimately resulted in the increase of onion growth and yield. Onion plants can be cultivated in the area where Arsenic containing water is being utilized for irrigating crops but, a chain of in-vitro studies are required to understand the biochemistry and mechanism that influenced growth and productivity of the onion plants.