Stevia (Stevia rebaudiana Bertoni) responses to NaCl stress: Growth, photosynthetic pigments, diterpene glycosides and ion content in root and shoot

Abstract

The aims of the experiment were to determine NaCl threshold and evaluate the effect of NaCl stress on the growth and physiological traits of stevia (sugerleaf). For these aims, a greenhouse experiment was carried out with six NaCl concentration levels (NaCl 0, NaCl 30, NaCl 60, NaCl 90, NaCl 120 and NaCl 150 mM). The plants were grown in pots and irrigated with Hoagland nutrient solution during 62 days. NaCl threshold and EC50 (the NaCl level that 50% of yield reduction) achieved 77.10 and 157.08 mM, respectively. NaCl stress caused reduction of plant height, leaf fresh and dry weight, chlorophyll a (Chl a), chlorophyll b (Chl b), total chlorophyll (total Chl), K+ content in root and shoot organs. On the other hand, NaCl stress caused an increase of malondialdehyde content (MDA), Na+ content in root and shoot and Na+/K+ ratio in root and shoot. The low level of NaCl (30 mM) indicated the highest of Chl a, carotenoids, total sugar, the percentage of Steviosides (Stev), Rebaudioside-A (Reb-A) and Stev+Reb-A. The finding of this study leads to the conclusion that, low level of NaCl concentration (30 mM) caused increasing steviol glycosides and the result showed stevia as a moderate NaCl tolerant plant. Keywords: Carotenoids, Chlorophyll, Potassium, Rebaudioside, Salinity threshold, Stevioside