Effects of aluminium toxicity on ion transport in Oryza sativa l. and Cicer arietinum l. in relation to biochemical and anatomical changes

Abstract

Aluminium, at concentrations of 10, 50, 100 and 150 µM, inhibited germination of rice and chickpea seeds. Aluminium stress decreased accumulation of K in the radicle and plumule of germinated rice and chickpea seeds. On the other hand, Cl - accumulation was increased by a maximum of 2- to 2.4-fold in the radicle and plumule of germinated rice and chickpea seeds following Al treatment. Similarly, Al (10-150 µM) caused a few fold increase in accumulation of Al 3+ in the radicle and plumule of germinated rice and chickpea seeds. Aluminium-induced decrease in K + content with concomitant increase in Cl and Al 3+ content in the radicle and plumule might be correlated with the inhibition of germination. Aluminium decreased K + accumulation in the root and shoot of rice, and the root, stem and leaves of chickpea seedlings grown in solution culture. On the contrary, different concentrations of aluminium caused a few fold increase in Na + in rice and chickpea. Aluminium stress caused a dramatic increase in Cl - accumulation in different parts of rice and chickpea seedlings. But aluminium toxicity decreased NO accumulation in rice and chickpea. Al stress decreased phosphate accumulation in rice and chickpea seedlings. Aluminium toxicity inhibited the accumulation of Ca 2+ , Mg 2+ and Fe in the root and shoot of rice, and the root, stem and leaves of chickpea plants grown in both solution and sand culture. in different parts of rice and chickpea seedlings grown in solution culture. Application of aluminium caused a dramatic increase in accumulation of Al Exposure of rice and chickpea seedlings to different concentrations of aluminium led to a stimulation of reducing and total sugar in the root, stem and leaves. Similarly, Al stress increased proline and total amino acid contents in different parts of rice and chickpea seedlings. Aluminium toxicity caused a dramatic increase in peroxidase and catalase activity in the root and shoot of rice. 150 µM Al caused a 8- to 9-fold increase in peroxidase and catalase activity, respectively, in the root of rice. On the contrary, Al stress decreased superoxide dismutase (SOD) activity in the root and shoot of rice. In chickpea, Al stress caused a few fold increase in peroxidase, catalase and SOD activity in the root and leaves. A dramatic 14.8- and 14.6-fold increase in SOD activity was recorded in the root and leaves of chickpea seedlings respectively. It is interesting to note that there is a generic difference between rice and chickpea with respect to the effect of aluminium stress on SOD activity. Aluminium toxicity caused a dramatic increase in phenolic compounds in rice and chickpea plants grown in sand culture. Aluminium stress resulted in a reduction of chlorophyll a, chlorophyll b and carotenoid contents in the leaves of rice and chickpea plants. Exposure to aluminium decreased primary root length and number of lateral roots in rice and chickpea seedlings grown in rhizobox. Aluminium toxicity inhibited the root and shoot length of rice and chickpea seedlings grown in solution culture. Aluminium stress decreased the dry weight of root and shoot of rice and chickpea seedlings. But it increased shoot/root dry weight ratio. Aluminium toxicity reduced the number of metaxylem vessels in the root of rice. Number of sclerenchyma cells were more in aluminium-treated rice root. Smaller sized vascular bundles were found in the leaf of rice under Al stress. In chickpea, Al decreased the size and number of vessels in the root. Number of palisade parenchyma was reduced in the leaf of chickpea. Al treatment caused closure of stomata both in rice and chickpea leaves. The effect of aluminium toxicity on ion transport and its correlation with biochemical changes and anatomical structure, and growth is discussed.