Drying rate and dehydrin synthesis associated with abscisic acid‐induced dehydration tolerance in Spathoglottis plicata orchidaceae protocorms

• Published in: Journal of experimental botany 2002-03, Vol.53 (368), p.551-558
• Main Authors: Wang, Xing‐Jun, Loh, Chiang‐Shiong, Yeoh, Hock‐Hin, Sun, Wendell Q.
• Format: Article
• Language: English
• Subjects: Abscisic acid; Abscisic Acid - pharmacology; Acclimatization - drug effects; Acclimatization - physiology; Agronomy. Soil science and plant productions; Biological and medical sciences; Blotting, Western; Calcium - analysis; Carotenoids - analysis; Chlorophyll - analysis; critical water content; Dehydration; dehydrin; desiccation tolerance; Drying; drying rate; Economic plant physiology; Electrolytes; Fundamental and applied biological sciences. Psychology; Heat-Shock Proteins - biosynthesis; Heat-Shock Proteins - drug effects; Moisture content; Orchidaceae - drug effects; Orchidaceae - growth & development; Orchidaceae - metabolism; Osmotic Pressure; Plant Growth Regulators - pharmacology; Plant physiology; Plant physiology and development; Plant Proteins - biosynthesis; Plant Proteins - drug effects; Plant Structures - drug effects; Plant Structures - growth & development; Plant Structures - metabolism; Plant tissues; Plants and the Environment; Potassium - analysis; Pretreatment; Protocorms; Sodium - analysis; soluble sugars; Spathoglottis plicata; Sugars; Water - metabolism; Water and solutes. Absorption, translocation and permeability; Water loss; Water relations, transpiration, stomata; water stress
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jexbot/53.368.551

Dehydration tolerance of in vitro orchid protocorms was investigated under controlled drying conditions and after abscisic acid (ABA) pretreatment. Protocorms were obtained by germinating seeds on Murashige and Skoog (MS) medium containing 10% (v/v) coconut water, 2% (w/v) sucrose and 0.8% (w/v) agar, and were dehydrated in relative humidities (RH) ranging from 7% to 93% at 25 °C. The critical water content of dehydration tolerance was determined, using the electrolyte leakage method. Drying rate affected the critical water content. Slow drying under high RH conditions achieved the greatest tolerance to dehydration. ABA pretreatment decreased the drying rate of protocorms, and increased dehydration tolerance. Improved tolerance to dehydration after ABA treatment was correlated with the effect of ABA on drying rate of protocorms. When critical water content of protocorms dried under different RH was plotted as a function of actual drying rate, no significant difference in tolerance to dehydration was observed between ABA‐treated and control protocorms. ABA pretreatment and dehydration of orchid protocorms induced the synthesis of dehydrin, especially under the slow drying conditions. ABA pretreatment also promoted dry matter accumulation such as carbohydrates and soluble proteins and increased the concentration of K+ and Na+ ions in protocorms. The ABA‐induced decrease in drying rate was correlated with lower osmotic potential, the enhanced maturity of protocorms and the accumulation of dehydrin in protocorms during pretreatment.