8342937071

CHAN GES IN GERMINATION, RESP1RATION RATĘ AND EEACHATE CONDUCTIVITY OF HEVEA SEEDS

PLRPUSTAKAAN

UNIVERSIT! PERTANIAN MALAYSIA

at 10°C leached highest followed by those seeds that were stored at 22°C and 27°C, respectively. Leachate conductivity wasquite lowatall tempera-tures because it was measured without removing the tesla, hence, the thickness of the testa might have prevented much of the leachate from leach-ing out. However, a signiflcant difference was observed between sto ragę temperaturesand months of storage. When whole soyabean seeds were used to measure leachate conductivity (Tilden and West 1985), the result was equivalent to the result ob-tainedin thisstudy. Ithasbeen reported thatthere is often a high correlation between leaching and reduction in vigour (Abdul-Baki 1980). Increase in leachate conductivity is considered to result from degradation of cellular membranes and sub-sequent lossofcontrol of permeability (Chingand Schoolcraft 1968). This is supported by Normah (1987) whoobserved tonoplastdissolution in Hevea seeds during storage.

The decrease in respiration ratę with months of storage at all storage tcmperatures correlates with the reduction in the integrityofmitochondria. With months of storage, mitochondria had less cristae and some developed electron dense depo-sits and loss of membrano integrity was common (Normah, 1987).

Some of the changes revealed in this study on Heueaseeds seem to be similar to those observed in previous studies on orthodox seeds. Decreased respiration associated with deterioration was reported in maize (Woodstock and Grabę 1967), wheat (Kittockand Law 1986),barley (Abdul-Baki 1969) and soybean (Leopold and Musgrave 1979) under natural ageing, accelerated ageingand chill-inginjury.

Changes that occurin Heveaseeds as shown in the present study may not be the only cause of deterioration of the seeds. Nevertheless, it was observed that imbibed storage of Hevea seeds was best at 27°C. Morę studies need to be carried out to find an improved method of storage of Hevea seeds as well as other recalcitrant seeds.

ACKN OWLEDGEMENTS

This study was carried out as a part of the first authors PhD thesis. The authors wish to thank Universiti Pertanian Malaysia for funding this project. The authors are also grateful to Prang Besar Research Station for the supply of seeds.

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