Changes of growth, photosynthesis and alteration of leaf antioxidative defence system of tea [Camellia sinensis (L.) O. Kuntze] seedlings under aluminum stress

Abstract

Tea [Camellia sinensis (L.) O. Kuntze] is an aluminum (Al) hyperaccumulator plant and is commercially important due to its high content of antioxidants. Although Al induced growth is well-known for the plants growing in acid soil, yet the cause underlying the stimulatory effect of Al has not been fully understood. To investigate the possible role of Al in growth induction, we studied morphological, physiological as well as biochemical changes of tea plant under different Al concentrations (0-4,000 μM). In hydroponics, Al (15 μM), enhanced shoot and root growth, but at higher concentrations, it caused oxidative damage which culminated in a cascade of biochemical changes, Al content increased concurrently with the maturity of the leaf as well as stem tissues than their younger counterparts. Hematoxylin staining indicated that Al accumulation started after 6 h of exposure in the tips of young roots and accumulation was dose dependent. The physiological parameters such as pigments, photosynthetic rate, transpiration and stomatal conductance were declined due to Al toxicity. Alteration in activated oxygen metabolism was also evidenced by increasing lipid peroxidation, membrane injury, evolution of superoxide anions and accumulation of H(2)O(2). Contents of phenols initially exhibited an acceleration which gradually plummeted at higher levels whereas total sugar and starch contents decimated beyond 15 μM of Al concentration. Activities of antioxidant defense enzymes were increased with the elevated concentration of Al. Expression of citrate synthase gene was up-regulated in the mature leaves, young as well as old roots simultaneously with increased concentration of Al in those parts; indicating the formation of Al-citrate complex. These results cooperatively specified that Al concentration at lower level promoted growth but turned out to be a stressor at elevated stages indicating the sensitivity of the cultivar (T-78) to Al.

Zinc stress induces physiological, ultra-structural and biochemical changes in mandarin orange (Citrus reticulata Blanco) seedlings

“…Nevertheless, stresses beyond tolerance levels unavoidably culminate in oxidative damage attributable to intensive production of ROS (Smirnoff 1993). Polyphenols, the major alkaloids, present in plants, are known antioxidant compounds (Mukhopadyay et al 2012(Mukhopadyay et al , 2013a and offer strong antioxidant activity in plants growing under heavy metal stress. Principally, they are oxidized by peroxidase and contribute in scavenging H 2 O 2 (Singh and Malik 2011).…”

“…Nevertheless, increased quantity of starch and sugar (Fig. 5c) could be involved in the superior growth of the Zn-optimum plants and these soluble carbohydrates probably provided energy and osmolytes necessary for growth (Mukhopadyay et al 2012).…”

Aluminium speciation and internal detoxification mechanisms in plants: where do we stand?

“…It is not clear if this mechanism can effectively prevent the inhibition of photosynthesis by Al, but tea plants can withstand Al concentrations that are toxic to many plant species without compromising the rate of photosynthesis. 48 According to a classification proposed by Wheeler et al…”

Effect of Zinc and Boron on Growth and Water Relations of Camellia sinensis (L.) O. Kuntze cv. T-78

“…It enjoys protracted life cycle and hence subjected to environmental stresses [1]. Generally, plants require elements as structural and catalytic components for normal growth [2] optimum availability of which is a prerequisite.…”