EFFECTS OF COLD TREATMENT ON MORPHOLOGICAL CHARACTERISTICS AND GROWTH RATE OF CAULIFLOWER (BRASSICA OLERACEA VAR. BOTRYTIS L.) SEEDLINGS

Three commercial cauliflower varieties were tested regarding the effects of cold treatments on morphological characteristics and growth rate and young transplants. A large number of graded seeds of early varieties were sown in pyramidal cells foam trays filled with peat compost in May 2010. The common seedling production technology was applied till the third true leaf was appeared to all seedlings. 20 day after sowing (20 DAS), 1/3 of total number of seedlings of each variety was enclosed into a refrigerator and kept inside at a 2 (+/-0.5) Celsius degree temperature. No artificial lightening was provided and the only source of light was the natural light comes through the glass made refrigerator door. The enclosed plants were split in three equal parts. Each of them was kept inside the refrigerator room for respectively 3, 5 and 7 days, and then brought back to the common production environment. The same was repeated with the next 1/3 of total number of seedlings in a more advanced age (30 DAS), while the last 1/3 of total number of plants were grew up in common commercial production conditions. Cold stress has negatively affected the relative growth rate (RGR) of cauliflower seedlings. Due to that, end of nursery period they have recorded a smaller dry weight (W) and leaf area (LA) compared to common non treated seedlings. Assuming that, exposure to relative cold conditions for one week was sufficient for curd initiation, and that the vernalization could be accomplished only after the juvenile phase is completed and a certain number of leaves were created, we conclude that cold treatment should be applied only to well matured seedlings, where, also, the adverse effects of cold stress are less severe