Abstract
The present work was conducting to study the strategy response of two broad bean cultivars Assiut 84 and Assiut 125 to different Cu2+ concentrations 100 ppm, 200 ppm, 300 ppm and 350 ppm in addition to control and interactions with IAA treatments. The dry matter exhibited the biphasic effect of Cu2+ on the growth criteria of the two broad bean cultivars. While the lower and moderate doses of Cu2+ (100 ppm and 200 ppm) stimulated the growth of the two cultivars, the higher doses revealed the opposite event where the growth dropped in both cultivars. This effect was more pronounced in cv. Assiut 84 than in cv. Assiut 125 and also at the higher Cu2+ concentration the growth dropped slightly in cv. Assiut 84 and highly significantly in cv. Assiut 125. The percent of increase in dry matter at 200 ppm in stem and leaf of cv. Assiut 84 was 120.45% and 155.31%, otherwise this percent of increase in these organs of cv. Assiut 125 was 114.29% and 131.41%. However the percent of reduction at 350 ppm Cu2+ in root and stem of cv. Assiut 84 was 74.13%, 79.23% and in root, stem and leaf of cv. Assiut 125 was 59.27%, 70.91%, 70.76% compared with control plants. Soluble carbohydrate in cv. Assiut 84 and cv. Assiut 125 was markedly increased while soluble protein was decreased in root, stem and in leaves at lower Cu2+ concentration. Also while Cu2+-stressed cv. Assiut 84 maintained potassium and magnesium levels around the control values and some promotion occurred especially in roots and stems, these cations dropped markedly in cv. Assiut 125 as a result of Cu2+ treatments. While Cu2+ had a marked stimulatory effect in the absorption and accumulation of calcium in the different organs of cv. Assiut 84, it, on the other hand, significantly inhibited the accumulation of this cation in the different organs of cv. Assiut 125. Treatments broad bean cultivars with Cu2+ plus IAA induced an increase in growth parameters, soluble suga, soluble protein, K+, Ca++ and Mg++ in different parts of two tested cultivars. The uptake, translocation and distribution of mineral ions are affected by various growth regulators among others by IAA. This strategy might be important in heavy metals tolerance mechanisms of crop plants.
Highlights
Heavy metals as Cu, Fe, Mn, Zn, Ni and AS include elements with densities above 5 g∙cm−3, but the term was extended to a vast range of metals and metalloids [1] [2] [3]
Diaz et al (2017) [3] showed that 50 μM and 100 μM of Cu2+ concentration induced a significant reduction in chlorophyll a content and exhibited oxidative stress evaluated through an increase in malondialdehyde levels on C. quitensis seedlings in vitro
Such contrasting results of Cu2+ effects on carbohydrates metabolism were found by Deef (2007) [30] who studied the effect of different concentrations of Cu2+ on Rosmarinus officinalis and reported that all carbohydrates fractions increased under Cu2+ treatments until 200 ppm as compared with control
Summary
Heavy metals as Cu, Fe, Mn, Zn, Ni and AS include elements with densities above 5 g∙cm−3, but the term was extended to a vast range of metals and metalloids [1] [2] [3]. High contents of trace elements have been found in numerous soils, which may become toxic for plants and other components of terrestrial biota [4] [5] [6]. Essential micronutrients are required in low contents to develop plant normally, but are toxic in high contents [5] [7] [8]. These can lead to physiological alterations, which are widely documented [9] [10]. Neto et al (2017) discuss the role of plant growth hormones abscisic acid, auxin, brassinosteroid and eythylene in signaling pathways, defense mechanisms and alleviation of heavy metal toxicity. The present work was conducted to compare the Cu2+ tolerance of the two selected broad bean cultivars Assiut 84 and Assiut 125 and ameliorating effect of IAA during vegetative growth of two broad bean cultivars
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