Browsing by Subject "juuristo"

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.

This thesis was undertaken to determine effects of genotype, vernalization and harvesting on the root growth of grass plants. Greenhouse experiments were carried out at Viikki experimental farm of University of Helsinki. The thesis was a part of a larger research of grasses. Grass species were two timothy (Phleum pratense L.) parental lines, northern (021/1) and southern (B112) genotype (Boreal Plant Breeding Ltd). The trial material was propagated using the plant material conserve of Viikki. A half of the trial material got a vernalization treatment (10 weeks) after pre-breeding (2 weeks, DL 12 h) and the other half of plants got only pre-breeding (3 weeks, DL 12h) before establishment of two separate trials in rhitsotubes and rhitsotrones. High, growth stage, dry matter of shoots and roots, depth of the root system and shoot to root ratios were measured from rhitsotubes seven times during the study. The growth samples from rhitzotrones were collected twice. The harvesting was done in the middle of the study from both separate trials. Genotype had an influence on all measured growth features in both separate trials. Treatments of southern genotypes were mainly higher, development was faster and dry matter of shoots was greater at harvest time compared to the same treatments of the northern genotype. There were no differences on growth features between genotypes in the end. The dry matter of roots was also greater at the harvest time with treatments of the southern genotype. In the end of the trial there were no differences between genotypes or treatments, but the genotype influenced on root growth in repeated measurements between weeks 6-8. The root system of the southern genotype spread out in deeper soil layers with both treatments and survived better after harvesting compared to treatments of the northern genotype. The vernalization had influence on growth features and the root system with most of the occasions of measurements with both the genotypes. The vernalization reduced biomass of roots in the both separate trials. This was partly due to low weight of shoots especially in the beginning of the study. In the other hand the vernalization improved on development before the harvesting and the carbohydrates allocated on shoots instead of roots. This was visible especially in the rhitsotubes. Differences between vernalized and non-vernalized treatments were levelled towards the end of the study. The vernalization increased growth of roots to deeper soil layers comparing to the non-vernalized treatment with the northern genotype. In weekly monitoring the growth of roots of both the vernalized genotypes were strong before ending the study. This might cite better overwintering but in the other hand shoot to root ratios were almost the same in all treatments. This study showed out that a plant tries to keep the growth of shoots and roots in balance but also that the biomass allocates in shoots in the beginning of the growing season and more in roots after harvesting. According to this study adding the southern genetic heritage to the timothy refinement programs brings higher yield level and moreover more abundant and deeper root system.