Heavy metal-hormone interactions in rice plants: Effects on growth, net photosynthesis, and carbohydrate distribution

Abstract

Abstract. The effect of external applications of gibberellins (GA3) and abscisic acid (ABA) on the growth, carbohydrate content, and net photosynthesis of heavy metal-stressed rice plants (Oryza sativa cv. Bahfa) was investigated. Treatment with cadmium (0.1 mM) and nickel (0.5 raM) inhibited rice growth and stimulated carbohydrate accumulation, especially in seeds from which seedlings were developing, stems, and first leaves. The addition of GA 3 (14 IJ.M) to the rice culture solution together with Cd or Ni partially reversed the effects of heavy metals, stimulating growth as well as mobilization of carbohydrate reserves in seeds from which seedlings had developed. GA 3 increased the sugar content in roots and second and third leaves and also modified the carbohydrate distribution pattern compared with heavy metal-treated plants. In contrast to GA 3, ABA (19 p.M) supplied to rice cultures potentiated the effect of heavy metals, inhibiting the growth of young leaves and the translocation of storage products from source to sink organs. In addition, sugars were accumulated in roots and second leaf but not in the third leaf, the extension in length of which was also inhibited by the treatment. Net photosynthesis rates recovered transitorily in Cd-treated plants after the addition of hormones. The possible relationship between growth and carbohydrate distribution, as well as the involvement of hormones, in the response of plant to heavy metal stress is discussed.

Effects of silicon nutrition on cadmium uptake, growth and photosynthesis of rice plants exposed to low-level cadmium

“…Cadmium-induced inhibition of growth has also been demonstrated to result from the accumulation of storage products at the expense of cell growth and elongation (Moya et al 1995;Verma and Dubey 2001). Furthermore, Chen and Huerta (1997) suggested that Cd-induced growth inhibition is due to an inhibition of photosynthesis.…”

“…It was reported that the consumption of rice grown in cadmium-polluted soils in Japan in the mid-1950s and mid-1960s was responsible for the human itai itai disease with symptoms that included joint pains and kidney malfunction (Herawati et al 2000). Symptoms of Cd toxicity in plants have been associated with leaf chlorosis, growth inhibition and the disruption of key physiological processes including photosynthesis (Atal et al 1991;Moya et al 1995;Das et al 1998;Chugh and Sawhney 1999;Kukier and Chaney 2002). Plants have evolved means of alleviating and tolerating heavy metal stress.…”

Evaluation of the protective role of exogenous growth regulators against Ni toxicity in woody shrub Daphne jasminea

“…Similarly, Meng et al (2009) did not observe any influence of exogenous GA3 on internal Cd accumulation in Brassica napus . This reaction was rather unusual, since GA3 was reported to be involved in alteration of the membrane permeability and regulation of membrane transport processes, leading to a decrease in metal uptake (Rubio et al 1994; Moya et al 1995). This reduction of Ni accumulation in GA3-treated plants was observed in Ni-hyperaccumulating species of Alyssum and Noccaea (Cabello-Conejo et al 2014) or non-accumulating specimens of Vigna radiata (Ali et al 2015).…”

Cadmium against Higher Plant Photosynthesis -a Variety of Effects and Where Do They Possibly Come From?

“…We cannot forget that also plant hor mones, regulating most of its physiological and metabolic processes, are influenced by Cd as well as many phenomena related to plant gene expres sion and translation (Moya et al, 1995;Shah and Dubey, 1995;Hollenbach et al, 1997).…”