--V. R. Bommineni, and E. Banasikowaska

The shoot apical meristems from 72 h imbibed mature seeds of maize, and immature grains of oat (summer grown crop plants), were used to examine the effect of a brief cold temperature (1 h) on the explant material. The plumules of maize and the immature whole grains of oat were surface sterilized in 10% "javex" for 30 min and exposed gradually to the low temperatures.

An 'Endocal Refrigerated Circulating Bath' (NESLAB, Model LT 50DD) was used to lower the temperatures at designated intervals. The samples were kept in a sterile test tube and the methanol temperature was lowered 1 C per every 5-10 min until the required temperatures were established (Tables 1 and 2). After attaining the appropriate temperature, the temperature was held at that level for 1 h and the samples removed. Similarly, the remaining samples were treated at different temperature levels for 1 h. Then the samples were kept (approximately 12 - 24 h) in a refrigerator (5 C) until the explants were cultured.

The shoot apical meristems were exposed under the microscope and transferred to Murashige and Skoog's nutrient medium (MNL 63: 87-88; Plant Cell Tissue Organ Culture 19: 225-234, 1989). After 2-3 weeks, the plantlets from the explanted meristems were transferred to pots in the glasshouse and grown in the glasshouse to maturity.

Table 1. Recovery of mature plants from cold shocked apical meristems (72h imbibed seeds).

Table 2. Recovery of mature plants from cold shocked young apical meristems of oat (var. Donald).

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