Die invloed van boor, trosvibrasie en relatiewe humiditeit van die trosatmosfeer op die bestuiwing van kweekhuistamaties (Lycopersicon esculentum L.)

[摘要] ENGLISH ABSTRACT:In South Africa tomato production in greenhouses normally occurs out of season when conditionsare unfavourable for production and for the pollination process. Pollination is of special importanceand the backbone of production. High temperatures contribute to the formation of abnormalities inflower morphology such as splitting of the anther cone and style exsertion. Low temperaturesinhibit growth of the anther cone and therefore the style is uncovered. The movement of pollenfrom the anther to the style is inhibited by the higher style position in relation to the anther cone.Under humid conditions the pollen tends to stick to the anther surface. Another factor contributingto the problem is the banning of European bumble bees in South Africa. Alternative methods ofpollen transport have to be found. Truss vibration, honey bees and plant growth regulators (PGR)are the most popular alternatives. Truss vibration and the use of PGR's are labour intensive andhoney bees tend to get disorientated inside a plastic greenhouse.During the first part of this study pollen from plants, grown at four different B-levels (0.02; 0.16;0.32 and 0.64 mg rl) was germinated in vitro. It was kept at different temperatures and periodsbefore incubating on different growth media. No proof was found that pollen from B-deficientplants germinated poorly. Germination of pollen decreased significantly after one week storage.Deterioration of pollen viability could be lowered by storage at 5°C. At least 10% sucrose is neededin the growth medium for in vitro germination but addition ofB had no positive effect.In a second phase of the study, the influence of the mentioned B application rates were tested.The experiment was done in a glasshouse where temperatures were mechanically regulated (22°Cand 10°C day/night). Seedlings of the greenhouse tomato cultivar, Abigail, were planted in acidwashed river sand. Plants were grown with the main stem trellised vertically and the side shootsremoved weekly. Only the first, third and fourth cluster were used for this part of the study. Theuptake of all the essential nutrient elements, fruit set, the relation of larger to smaller fruits, physicaland chemical quality and fruit shelf life were evaluated. The application of B at higher ratesincreased the uptake of Ca and decreased K-uptake. Fruit set, fruit development, fruit color andshelf life were the best at a B-Ievel of 0.16 mg r'. At this rate the abortion of flowers was the least.The same plants were used for the second part of the study, using the third cluster. The influenceof the same four B-Ievels, the relative humidity (RH) of the truss atmosphere and truss vibrationswere tested. The second cluster was covered with a plastic bag. Dry {

[发布机构] Stellenbosch University