Role of the Cotyledon in Sensitivity to Cold of Cacao Seed

Abstract

IT has been shown by Boroughs and Hunter¹ that cacao seeds are quite sensitive to cold. Viability of the seed, measured by germination and growth, is reduced to a low percentage by treatment at 6° for 8 min. My previous investigations have shown that treatment at 4° for 10 min is sufficient to inhibit growth of the seed completely, although post-treatment at 37° for 10 min restores 85 per cent viability to the seeds^2,3. After 15 min at 4°, no amount of post-heat treatment at 37° will restore viability to the seeds³. It became necessary to pin-point the locus affected by cold in the seed. Since I had succeeded in growing excised cacao embryos in sterile culture⁴ and, with Casas⁵, had successfully measured respiration in cacao embryos using a Warburg respirometer, a simple method of separating the cacao embryo from the cotyledonary material presented itself.