biologia plantarum

Biologia plantarum 51:355-358, 2007 | DOI: 10.1007/s10535-007-0072-2

Effects of brassinosteroid infiltration prior to cold treatment on ion leakage and pigment contents in rape leaves

A. Janeczko^1,*, G. Gullner², A. Skoczowski¹, F. Dubert¹, B. Barna²

¹ The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Krakow, Poland

² Plant Protection Institute, Hungarian Academy of Sciences, Budapest, Hungary

The effect of 24-epibrassinolide (BR₂₇) on cold resistance of rape seedlings was studied by ion leakage and photosynthetic pigment degradation measurements. Aqueous solutions of BR₂₇ were injected into cotyledons or primary leaves of rape plants and these plants were incubated at 2 °C or 20 °C. Cold treatment (2 °C) without BR₂₇ injection elevated the membrane permeability in both primary leaves and cotyledons significantly. Surprisingly, injection of leaves with water or 0.467 % aqueous ethanol solution led to a massive increase in membrane permeability after cold stress at 2 °C. The synergistic effect of leaf infiltration and cold on permeability was abolished by 0.05 and 1.00 µM of BR₂₇ in primary leaves and by 1.00 µM of BR₂₇ in cotyledons. On the other hand, BR₂₇ solutions strongly elevated the membrane permeability at 20 °C, while water and ethanol solutions brought about only negligible increases. Water or ethanol infiltrations strongly reduced the leaf contents of chlorophyll (Chl) a, Chl b and carotenoids at 2 °C but less markedly at 20 °C. However, in seedlings exposed to 2 °C pigments content was significantly higher in BR₂₇-treated leaves as compared to water/ethanol control. There were no differences between pigment contents of leaves injected with BR₂₇ solutions or only water/ethanol at 20 °C. The above data strongly support the stress protecting effect of BR₂₇.

Keywords: carotenoids; chlorophyll; cold stress; 24-epibrassinolide; ion leakage

Subjects: Brassica napus; brassinosteroids; chlorophyll a,b; cold stress, acclimation, low temperature; cotyledon, cotyledonary node; ion leakage; photon flux density (PPFD, PFD)

Received: June 29, 2005; Accepted: March 28, 2006; Published: June 1, 2007  Show citation