2Seed Moisture: Recalcitrant vs. - PDF document

2Seed Moisture: Recalcitrant vs. Orthodox Seeds' H. F. Chin and B. Krishnapillay Universiti Pertanian Malaysia P. C. Stanwood USDA -ARS The terms orthodox and recalcitrant seeds came into usage in 1973. Roberts20 g' fresh wt., fw)2 and tolerated freezing temperatures.20 g' fw),2O g' fw) and could not tolerate freezing temperatures. Because of thesedesiccation sensitive moreand longevity of both recalcitrant and orthodox seeds. 2O g €1 fW)20 g' fw). As a result, the methods, techniques, packaging materials,reviewed with particular emphasis on seed moisture content. 'Contributions from the Agronomy and Horticulture Dep., Universiti Pertanian Malaysia, USA. Seed Moisture, CSSA Special Publication no. 14. 15 16 MOISTURE DETERMINATION The International Seed Testing Association (ISTA) has published rules1985), two 5.0-g samples of seeds are used for the determination of seedmoisture content. High and low temperature air-oven methods of 130 to(Zea mays L.), ground samples are re- to 105‚C except for Abies, Cedrus, Fagus, Picea, and Tsuga for which thePlan (anus occidentalis L., Liquidambar styracifona L., and Fraxinus penn-Marsh. 5.0-g drying samples are notadequate in size, which makes sampling difficult. The number of seeds thatfor testing and the number of seeds available for an experiment should be DIFFERENCES BETWEEN RECALCITRANT AND Recalcitrant and orthodox seeds differ greatly in their ecology andseeds not only in size but also complexity and viability. Many recalcitrant(Cocos nucifera L.). Generally, RECALCITRANT AND ORTHODOX SEEDS shape and size of cotyledons and the embryonic attachment compared to bean(Phaseolus vulgaris L.), a typical example of an orthodox seed. Moisture Content of Recalcitrant and Orthodox Seeds At physiological maturity, the moisture contents of recalcitrant seeds25 mm)(Durio zibethinus Murr.). Nephelium lappaceum L. Artocarpus heterophyllus Lam. Artocarpus champeden (Lour.) Spreng. Lansium domesticum Corr. Bouea ganadaria22 x 15 Durio zibethinus Murr. Theobroma cacao L. Hibiscus esculentus L. Vigna sesquipedalis (L.) Fruw. Pisum satioum L. Phaseolus oulgaris L. Glycine max (L.) Merr. Vigna sesquipedoiis (L.) Fruw.Hibiscus esculentus L. Artocarpus heterophyllus Lam.Nephelium lappaceum L. 18 The distribution of moisture content in the embryo and whole seed forcontent, however, because of their smaller size. In the case of recalcitrant THE IMPORTANCE AND PROBLEMS OF SEED MOISTUREIN RECALCITRANT SEEDS High moisture contents of recalcitrant seeds makes them sensitive to(Theobroma cacao) andHevea seeds rapidly lose germination when they are dried to 0.26 and 0.20to 0.02 to 0.04 g H and orthodox seeds with their coefficients of variation. Nephelium lappaceum L. Artocarpus heterophyllus Lam.Artocarpus champeden (Lour.) SpringLansium domes ticum Corr. Bouea ganadaria Murr. Theobroma cacao L. Hibiscus esculentus L. Vigna sesquipedalis (L.) Fruw. 0.749 0.493 0.483 0.291 0.126 RECALCITRANT AND ORTHODOX SEEDS they are less likely to be affected by minor fluctuations in relative humidities(Citrus limon L.) (Mumford & Grout, 1979) and cassava(ManihotCrantz) (Ellis et al., 1981). Therefore, the correct diagnosis and Shorea ovalis (Sasaki, 1976), andDrybalanops aromatica (Jensen, 1971). The loss in viability of cocoa seeds(1963) suggested three possible reasons for this rapid decline in germination (Artocarpus heterophyllus Lam.), 20 8016 of the seeds can germinate inside the ripe fruit. Farrant et al. (1986)attributed this early germination to the advanced maturity of recalcitrant(Gar-(Winters & Rodriquez-Colon, 1953) and rambutan(Nephelium lappaceum L.) (Chin, 1975). Chemical inhibitors also have been Finally, high moisture in recalcitrant and orthodox seeds is a problem FUTURE RESEARCH Roberts et al. (1984) have suggested that the most promising method(Sesamum indicum L.) to 0.285 g H(Artocarpusand Drybalanopshave survived cryopreservation. Culturing these species in enriched(Hevea brasiliensis), a true recalcitrant species, has em- RECALCITRANT AND ORTHODOX SEEDS have failed. The in vitro technique using cryopreserved embryos may prove CONCLUSION Improvement in seed science technology has advanced rapidly over theprescribed by ISTA. REFERENCES Bonner, F.T. 1972. Measurement of moisture content in seeds of some American hardwoods. (Nephe/ium lappaceum) seeds. Malays. Hevea brasiliensis. Seed Sci. Technol. 9:411-422. Cochran, W.G. 1953. Sampling techniques. John Wiley and Sons, New York. Farrant, J.M., N.W. Pammenter, and P. Berjak. 1986. Recalcitrance€A current assessment. Melicoccus bijugaf us and Eugenia brasiliensis (E.using abscisic acid as a germination inhibitor. Seed Sci. Technol. 7:403-406. 22CHIN ET AL. Hot, Y.L. 1984. Storage of cocoa (Theobroma cacao) seeds and changes associated with their (Theobroma cacao) seeds. Seed Sci. Technol. (Drybalanops aromaticaGaertn.). Proc. Int. Seed Test. Assoc. 36:141-146. (Elaeis guineensisJacq.) seeds. Proc. mt. Seed Test. Assoc. 37:751-761. Citrus limon seed. Seed Sci. Technol. 7:407-410. Hevea brasiliensis Muell-Arg. Pertanika 9:299-303. In J.H.W. Holden and J.T. Williams (ed.) Crop genetic resources: Conservation In H.F. In K.K. Kartha (ed.) Cryopreservation of plant cells and organs. CRC Press, Boca Raton, In W.Heydecker (ed.) Seed ecology. Butterworths, London.