Browsing by Subject "astiaviljely"

This study investigated the frost hardiness of cranberry (Vaccinium macrocarpon Ait.) in four cultivars (’Early Black’, ’Howes’, ’Pilgrim’ and ’Stevens’), focusing especially on the frost hardiness of roots in soilless cultivation. Plants for the study were forced in a greenhouse from cuttings of mother plants. The cuttings were rooted in pots diameter of 10 cm x 10 cm in forest peat. Plants were set to grow in the high tunnel over the growing season. Two experiments were conducted during winter 2020–2021. In the experiments, whole plants with pots were exposed to freezing treatments in a controlled freeze chamber at the temperatures of -10, -15, -20 and -30 °C. Control plants were exposed to cooling at +2 °C for an equal time. In the first experiment, plants were exposed to freezing treatment in November straight from the high tunnel. The second experiment took place in January, and plants were overwintered outside until the experiment. After the freezing treatment one upright in each plant was cut, set in a glass tube containing distilled water, and forced in the greenhouse for 14 days. The vitality of the buds, leafs and stems in the cuttings was observed with a stereomicroscope. After the freezing treatment the vegetative growth of the plants grown in pots was cut off exluding the main shoot, which was cut 5 cm above the soil surface. Thereafter plants were forced in the greenhouse over 10 weeks (the light period of 18/6 h, temperature +20 °C). The vitality of the roots was determined by measuring the amount of the new vegetative growth. All the plants tolerated -10 ° C freeze in November and -15 ° C in January, respectively without injury. Some new growth was observed in plants exposed to freezing treatments of -5 ° C below the temperature mentioned above, but frost damage occurred, and the re-growth was decreased compared to control plants. Cultivar Stevens was more tolerant than the others in both experiments conducted. It maintained its growth potential after -15 °C freezing treatment in November, and -20 °C in January respectively. Frost hardiness (LT50) of buds ranged in November from -19 °C to -27 °C. In January ’Stevens’ buds had the highest frost hardiness (LT50 =-36 °C) and ’Pilgrim’ buds had the lowest (LT50 =-27 °C). The environmental conditions throughout the whole growing season may affect frost hardiness, thus, this experiment should be repeated for verifying the results obtained. Also the potential impact of dormancy in the experiment conducted in November cannot be ignored.