EFFECT OF FLUORIDE AND SALICYLIC ACID ON ... - Semantic Scholar

Keywords: Biochemical parameters; Chlorophyll a and b; Chlorophyll stability index. Fluoride toxicity in plants; Membrane stability index; Phenols; Pigments; Salicylic acid; Seedling growth;. Sugars; Watermelon (Citrullus lanatus). INTRODUCTION. Chronic fluoride (F) exposure causes diverse toxic effects in both humans. 1.
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49 Research report

Fluoride 47(1)49–55 January-March 2014

Effect of fluoride and salicylic acid on seedlings of watermelon Ram, Verma, Gadi

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EFFECT OF FLUORIDE AND SALICYLIC ACID ON SEEDLING GROWTH AND BIOCHEMICAL PARAMETERS OF WATERMELON (CITRULLUS LANATUS) Amra Ram,a Pooja Verma,a BR Gadib Jodhpur, India

SUMMARY: The effect of sodium fluoride (NaF) on seed germination and biochemical parameters were studied in in vitro grown seedlings of watermelon (Citrullus lanatus) under salicylic acid (SA) treatment. After seven days of NaF treatment, reductions were observed in percentage of seed germination, root and shoot length, vigor index, pigment content, chlorophyll stability index (CSI), and membrane stability index (MSI) with increasing concentrations of NaF (1 and 10 mM). Seedlings treated with SA, both alone and in with combination of NaF, showed an increase in seed germination as well as other growth parameters. NaF-treated seedlings were found to accumulate more soluble sugars and phenolics, which were further increased by SA treatment thereby indicating a synergistic effect of SA and NaF on the accumulation of sugars and phenols. Therefore, these parameters are not directly related to a higher vigor index, membrane stability, and seedling growth. Treatment with SA reduced the adverse effects of NaF by increasing seed germination, root and shoot length, vigor index, pigment content, CSI, and MSI by some mechanism other than the accumulation of sugars and phenols. The possible reasons for the ameliorative effects of SA in seedlings of watermelon growing under F stress are discussed. Keywords: Biochemical parameters; Chlorophyll a and b; Chlorophyll stability index. Fluoride toxicity in plants; Membrane stability index; Phenols; Pigments; Salicylic acid; Seedling growth; Sugars; Watermelon (Citrullus lanatus). INTRODUCTION

Chronic fluoride (F) exposure causes diverse toxic effects in both humans1 and animals.2 F is not an essential element for the normal growth of plants and in higher concentration it is toxic for plants, especially for early seedling growth.3 Seed germination and early seedling growth are important phases for the successful growth and survival of plants and these physiological parameters of plants are greatly affected by NaF at different concentrations due to its inhibitory activities.3,4 Several physiological and biochemical processes are known to be markedly affected by F such as chlorosis and necrosis of leaf, inhibition of the nutrient uptake, reduction of plant growth, and enzyme activities.4-7 In India, several states are F endemic8 including Rajasthan where ground water contains a high amount F in all the 33 districts.9 In Rajasthan, due to irregular and low rainfall and recurrent drought, ground water is the main water source for irrigation for agricultural purposes. In addition, the soil of northwest Rajasthan contains elevated F due to the excessive use of diammonium phosphate fertilizers.10 Salicylic acid (SA) is a phenolic compound which plays an important role as a signaling molecule for the regulation of several physiobiochemical processes in plants.11,12 Through changes in hormonal levels, it plays protective roles in plants aDepartment

of Botany, Jai Narain Vyas University, Jodhpur 342005, India; bFor correspondence: Dr BR Gadi, Associate Professor, Department of Botany, Jai Narain Vyas University, Jodhpur 342005, India; E-mail:[email protected]

50 Research report

Fluoride 47(1)49–55 January-March 2014

Effect of fluoride and salicylic acid on seedlings of watermelon Ram, Verma, Gadi

50

against pathogens and many abiotic stresses including drought, salt, and heavy metals.12,13 Watermelon (Citrullus lanatus) is a fruit crop in the arid region of Rajasthan.14 It is used to flavor summer drinks and smoothies in the region, where the temperature may rise up to 50ºC during the summer season. Seeds of watermelon are demulcent, diureti