Vol. 74 No: 3

Title:
The effects of radiation frost on freezing damage and apical abortion in calabrese (Brassica oleracea var. italica) transplants

Authors:
JANE L. FORSYTH, J.R. BARNETT, S. PEARSON, P. HADLEY and M.P. FULLER

pp: 401-406

Abstract:
Freezing damage has been reported to be associated with apical abortion (blindness) in calabrese, preventing the formation of a marketable head. In the past, laboratory based experiments studying the freezing of whole plants using convective freezing have resulted in death of the plants while failing to induce blindness. Using a unique radiation freezing facility, capable of reproducibly simulating glasshouse frost conditions, we investigated the effect of hardening and freezing duration on calabrese transplants. Four cultivars were raised and subjected at four different growth stages (3, 5, 7 and 9 leaves) to a factorial combination of frost (0-4 d of frost between -2 to -4°C) and hardening regimes (0-6 d at 4°C prior to freezing). Following each frost/hardening treatment, half the sample was dissected and the remainder potted up and grown on. Light and transmission electron microscopy of the dissected plants revealed that the apical region of all the varieties at each of the growth stages remained intact following all frost treatments applied. No significant apical abortion was recorded. No blind plants were recorded following a repeat of the experiment using commercially grown plants (cv. Marathon). It was observed that the apical region of the calabrese transplants has a high degree of frost tolerance and that freezing conditions alone are not responsible for the induction of apical abortion.

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