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Thesis (MTech (Horticulture))--Cape Peninsula University of Technology, 2018. / This study evaluated the effects of 5 different soaking treatments in conjunction with 5 varying irrigation intervals on the germination, growth and nutritional values of seed of Hordeum vulgare Sv13. The 5 different soaking times consisted of 1, 3, 8, 16 and 24 hours. The barley seed was first cleaned and then placed in a vessel containing 500 ml of distilled water with a 20 % solution of sodium hypochlorite (bleach) at room temperature. Thereafter the pre-soaked seeds were transferred to a perforated container, containing no medium and placed into a growing chamber equipped with drip irrigation. The seed was then irrigated with 1245 ml of water at 5 different intervals namely every 2, 4, 8 10 and 12 hours. The temperature of the hydroponic growing room was kept at a constant 23 °C using a hotoperiod of 16-hour day/ 8-hour darkness. The seed was allowed to germinate and grow for a period of 8 days before being harvested. The objectives of this study were to determine the most beneficial combination of soaking treatment in conjunction with the most beneficial irrigation interval on the germination rate of the seed allowing for radicle emergence and coleoptile production. It was also used to determine which combination of treatments was most beneficial to the growth and nutritional values of the seed post-harvest. Another objective was to ascertain the shortest soaking time for application in a small-scale, hydroponic growing unit as well as the frequency of irrigation required to grow seedlings, thereby determining the amount of water required to produce a seedling mat for a small-scale, subsistence farmer, with the emphasis being on water reduction. Each treatment was replicated 10 times and consisted of 500 grams of seed, which when placed into its container measured 2 centimetres in depth, totalling 25 treatments in all. Germination was measured by observing radicle emergence in the first 2 days of the growing period first after a 24-hour cycle and again after 48 hours. The numbers of leaves present at harvest after an 8-day growing period were also counted to determine germination rate of the seeds. Growth was determined by average leaf height as well as the tallest leaf on day 8 of the growing cycle. Root mat expansion was also measured, post-harvest, which was compared to the initial 2 cm planting depth of seed. Wet and dry weights of the plant material were measured post-harvest. Samples of the harvested material were also sent for nitrogen and protein analysis. It was discovered that most of the results favoured a shorter soaking time and an increase in irrigation frequency, bar a few exceptions. Most favoured a pre-soaking time of only 1 hour together with an irrigation frequency of between 2 and 4 hours. This shows that small-scale farmers would be able to reduce the time spent on soaking of their seed. Although the frequency of the irrigation interval remained high further testing would be required to determine if the amount of water applied at each irrigation interval could be reduced and still produce favourable results. It would also remain to be seen if no irrigation during the 8-hour dark photoperiod would have any negative impact on germination, growth and nutritional values of the seedlings.

Graduation date: 1991

Plant growth regulator(s) (PGR) can be used as lodging inhibitors and/or yield promoters for spring barley (Hordeum vulgare L.). From 1987 to 1990 four field experiments were conducted to monitor barley main-stem apical development and to determine the effects of chlormequat (CCC) and ethephon on the development, physiology and yield of spring barley. Our data provide a description of barley apical development and the general pattern of leaf and spikelet primordium production under field conditions. In general, PGR treatment reduced the apical dominance of dominant sinks allowing the survival and greater development of more subordinate sinks. Early application of either CCC or ethephon retarded development of the main-stem apex from shortly after application to the awn elongation stage and reduced the number of aborted spikelet primordia, thus increasing the potential number of grains per spike and sometimes grain yield. Ethephon applied at ZGS 39 reduced plant height and lodging. Early application (ZGS 30) of ethephon, alone or in combination with CCC increased the number of spikes m$ sp{-2},$ but not grain yield. The number of spike-bearing shoots per unit area or per plant was increased by early PGR treatment, primarily by enhancement of tiller number rather than tiller survival. Early application of CCC or ethephon to spring barley is not justified, and caution must be taken when using ethephon at the currently recommended rate and stage for lodging control. Post-anthesis application of ethephon can efficiently enhance grain fill and yield of spring barley.

The enormous burning of fossil fuel and deforestation have caused an increase in the atmospheric CO₂ concentration ([CO₂]) during the last century. This will invariably have profound direct and indirect effects on plant carbon metabolism. The majority of research on the effects of CO₂ enrichment on plants are short-term and are done on other crops, but very little have been done on barley. This project aimed to determine the effects of long-term CO₂ enrichment on photosynthesis, growth and grain yield on barley. Hordeum vulgare L. cvs Stirling and Schooner plants were grown from seeds in controlled environment chambers at ambient (350) and elevated (600) μmol molˉ¹ [CO₂]. Measurements of net assimilation rate (NAR), photosynthetic pigments content and growth parameters were started 7 days after germination (DAG) and continued until senescence. The anatomy of matured fully developed leaves was also monitored. Elevated [CO₂l resulted in an increase in NAR in the two cultivars from days 7 until 14, after which the stimulation of NAR of CO₂-enriched plants started to decrease. At the onset of senescence, NAR was almost equal in plants grown under both ambient and elevated [CO₂]. The response of assimilation as a function of internal [CO₂l (C₁) at the end of the experimental period showed a significant decrease in both the initial slope of the A/C₁ curves and the CO₂-saturated photosynthetic rates in the two cultivars. Stirling showed no significant changes in the content of chlorophyll α,chlorophyll б or in total carotenoids. However, Schooner showed a stimulation in chlorophyll α content at day 7, but decreased at day 28. Chlorophyll б and total carotenoids content were not affected by CO₂ enrichment. While total above-ground biomass was not affected by elevated [CO₂] in the two cultivars, total plant height decreased significantly after 14 days in Stirling whereas no significant change occurred in Schooner throughout the experimental period. Leaf area was not significantly affected by CO₂ enrichment in the two cultivars although the leaves in CO₂ enriched plants were slightly shorter. Anatomical studies reveal that leaf thickness was significantly increased by CO₂ enrichment in Stirling, but the increase was not significant in Schooner. Both cultivars did not show any significant effect on chloroplast morphology and ultrastructure as a consequence of elevated CO₂ exposure. No signs of starch accumulation were evident in variety Schooner, but Stirling showed some form of starch accumulation, under increased atmospheric [CO₂]. Elevated CO₂ resulted in a significant reduction by more than 50 % in the number of grain yield per plant in both Stirling and Schooner. Results from this study therefore indicate that CO₂ enrichment will not be beneficial in terms of growth and yield in this important crop.

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