Kinetin-Mediated Prolongation of Viability in Recalcitrant Sal (Shorea robusta Gaertn. f.) Seeds at Low Temperature: Role of Kinetin in Delaying Membrane Deterioration during Desiccation-Induced Injury K. S. Krishna Chaitanya and S. C. Naithani* Seed Biology Laboratory, School of Studies in Life Sciences, Pt. Ravishankar Shukla University, Raipur 492 010 (M.P.), India Received October 7, 1997; accepted January 27, 1998 Abstract. The effects of kinetin (6-furfurylaminopu- rine) on viability during storage of recalcitrant sal (Sho- rea robusta Gaertn. f.) seeds at low temperature (15°C) were investigated. The freshly mature sal seeds showed an absolute loss of viability within 6–7 dah (days after harvest) when stored at ambient or at 15°C (control). Storage of these seeds at 15°C after kinetin (10 ppm) treatment prolonged the viability period up to 35 days with 20% germination. The kinetin-treated seeds exhib- ited 100% germination up to 10 days compared with 3 days in controls. Measurements of leachate conductivity, O - 2 and lipid peroxidation registered gradual increases from 0 dah onward to 35 dah with significantly low levels compared with controls. On the other hand, an enormous increase in superoxide dismutase activity was discernible for a longer duration (0–35 dah) in kinetin- treated seeds than in control seeds where it remained for 3 dah. The role of kinetin in prolonging seed viability by reducing the loss of leachates, lipid peroxidation, O - 2 , and enhancing of superoxide dismutase is discussed. Key Words. Seed viability—Oxidative stress—Exten- sion—Kinetin recalcitrant–Shorea robusta (Sal) Sal (Shorea robusta Gaertn. f.) makes up almost 14% of the total forest cover of India (Joshi 1980). It is valued for its timber and for the oil from its seeds. The seeds are short lived under natural conditions; storage and trans- port problems have hindered the establishment of plan- tation and species trials (Tompsett 1985). These prob- lems indicate the importance of developing methods for extending the storage life of the seeds. Like many other recalcitrant seeds, sal seeds do not show maturation drying. They are shed from the parent plant at high moisture content (42–49%). The recalcitrant nature of sal seeds excludes all traditional methods of storage. The rapid loss of moisture content and concomi- tant loss of germination, particularly below the relatively high LSMC (lowest safe moisture content) value, in al- most all recalcitrant seeds, has posed a great challenge in their storage (Chin and Roberts 1980). Because the physiology of development and storage of recalcitrant seeds (Berjak et al. 1990) are altogether different from those of orthodox seeds, attempts have been made to develop new storage methods. The temperate-recalcitrant species, such as Quercus and Aesculus, have seeds that cannot be dried at all, but they can be stored for several years (1–3 years) at near freezing temperatures (3 to -3°C) with marginal loss in viability (18–35%) (Bonner and Vozzo 1987, Tylkowski 1984). On the other hand, the seeds of tropical recalcitrant species have the same high moisture requirement as the temperate-recalcitrant species, but they are sensitive to low temperature (Chin and Roberts 1980, Yap 1986). Even short periods of storage at chilling temperatures will cause rapid loss of viability. Included in this group are many Shorea species (Purohit et al. 1982, Yap 1986), Theobroma cocoa (King and Roberts 1979), Hopea species (Song et al. 1984), and several tropical forest tree seeds (Chin and Roberts 1980). In general, the viability of most of the tropical recal- citrant seed species can be prolonged, for a limited pe- riod, when stored at low temperatures (13–15°C). For example, sal seed viability was extended over a period of Abbreviations: LSMC, lowest safe moisture content; SOD, superoxide dismutase; RH, relative humidity; DW, distilled water; TBRS, thiobar- bituric acid-reactive substance(s); MDA, malondialdehyde; FW, fresh weight; PVP, polyvinylpyrrolidone 40; dah, days after harvest. *Author for correspondence. J Plant Growth Regul (1998) 17:63–69 © 1998 Springer-Verlag New York Inc.