Effect of light intensity on trend of chlorophyll fluorescence parameters changes in stevia (Stevia rebaudiana Bertoni) medicinal plant under cold stress
Subject Areas : Journal of Plant Ecophysiology
Mehranoosh Emamian Tabarestani
1
(گروه زراعت و اصلاح نباتات، دانشگاه علوم کشاورزی و منابع طبیعی ساری، ساری، ایران)
Esfandiar Farahmandfar
2
(گروه زراعت و اصلاح نباتات، دانشگاه علوم کشاورزی و منابع طبیعی ساری، ساری، ایران)
Hemmatollah Pirdashti
3
(پژوهشکده ژنتیک و زیست‌فناوری کشاورزی طبرستان، دانشگاه علوم کشاورزی و منابع طبیعی ساری، ساری، ایران)
Yasser Yaghoubian
4
(پژوهشکده ژنتیک و زیست‌فناوری کشاورزی طبرستان، دانشگاه علوم کشاورزی و منابع طبیعی ساری، ساری، ایران)
Keywords: Physiological traits, Low temperature, photosystem, quantum yield,
Abstract :
In order to evaluate the joint effects of cold and light stresses on chlorophyll fluorescence parameters in stevia (Stevia rebaudiana Bertoni), an experiment was done in a factorial arrangement based on a completely randomized design with three replicates. Treatments were five levels of cold stress (0, 4, 8, 12 and 16 days) at 6±2 ᵒC and three light intensity levels of normal light, 50 and 10 % of normal light (240, 120 and 24 µm.m-2.s-1, respectively). Plants were kept in controlled conditions for 30 days then chlorophyll fluorescence parameters were measured. Results showed that Fv/Fm and Fv/Fo in response to cold stress changed in reduce trend and was described by a segmented model. Accordingly, these parameters increased linearly until twelfth day with a soft slope (0.0007 and 0.0149, respectively) and then decreased with a sharp slope (0.0074 and 0.1098, respectively). Also, Fm, Fv, Ft, Fm' only linearly respond to cold stress when stevia plant grown at 240 and 120 µm.m-2.s-1, while in 24 µm.m-2.s-1 the response of plant was fitted by a segmented model in which linearly decreased and then increased. Furthermore, Y(II) adversely affected by cold stress in all light intensity levels while Y(NPQ) and Y(NO) increased particularly in 240 µm.m-2.s-1. In conclusion, the results suggest that chlorophyll fluorescence parameters are sensitive to cold stress particularly when stevia plant exposed for a prolonged period of time and higher light intensity.