K. Waithaka

The effect of duration of cold treatment on growth and flowering of liatris

Abstract Dry corms of Liatris spicata L. ‘Gloriosa’ (gay-feather) were stored at 3–5°C for 12, 10, 8, 6, 4 or 2 weeks, before being planted and forced outdoors at 21–25°C day temperatures and 10–14°C night temperatures. Low-temperature treatment at 3–5°C was necessary to obtain satisfactory shoot growth and flowering after planting. The rate of plant emergence, shoot growth and the percentage of flowering increased with increasing duration of cold treatment. The period from corm planting to flowering was inversely related to the duration of the cold treatment, optimum duration resulting in early flowering, more uniform flowering and an increase in length of the inflorescences. The non-cold-treated corms, or those which received inadequate low-temperature treatment, resulted in poor and slow plant emergence, many non-flowering shoots and very slow stem elongation for both flowering and non-flowering shoots.

EFFECTS OF GROWTH REGULATORS AND GENOTYPES ON PYRETHRUM IN VITRO

SummaryThe effects of growth regulators on culture response of different pyrethrum (Chrysanthemum cinerariaefolium Vis.) genotypes were investigated. In the genotype Sb/66/107, the presence of 2,4-dichorophenoxyacetic acid (2,4-D) at 2 mgl−1 promoted growth of callus, whereas benzyladenine and 1-naphthaleneacetic acid had no effect. Callus growth was also affected by the 2,4-D, ranging from 0.5 mgl−1 for genotype Marwanga to 3.0 mgl−1 for Ks/75/336. Among the genotypes, shoots were regenerated from calluses of Sb/66/107, 4331, Marwanga, and MA/70/1013.

THE INFLUENCE OF TREE TRAINING AND PLANT DENSITY ON GROWTH, YIELD COMPONENTS AND YIELD OF ARABICA COFFEE CV. RUIRU 11

Assessment of tree growth and yield components of Coffea arabica L. cv. Ruiru 11, as influenced by tree training on single or two-stem systems at densities between 1600-4800 trees per ha during the first production cycle was carried out at Ruiru, Kenya over three years. Trees trained on the two-stem system tended to be taller than those on singlestems. Although the results were not clear, trees at low plant densities had thicker stems irrespective of the training system. The total number of primary branches was significantly higher on trees trained on the two-stem system. However, bearing primaries and productive wood were higher on the single-stem system during the first year of production. The number of bearing primaries and productive wood increased in subsequent production years on the two-stem system. Training trees on the two-stem system significantly depressed yields in the first production year by 245 to 842%, irrespective of plant density. Yields of clean coffee increased significantly with tree ...

Flowering of cabbage and kale in Kenya as influenced by altitude and GA application.

SummaryIn Kenya, at Kabete (1941 m), GA3 applications at 100 and 250 mg 1−1 promoted flowering in cabbage cvs Sugar Loaf and Giant Drumhead but cv Golden Acre did not flower. The same levels of GA3 promoted flowering in kale cv Collards, but failed in cv Thousand Headed. There was a small percentage of natural flowering in all cabbage and kale cvs that flowered. At Molo (2554 m), Sugar Loaf flowered with and without GA3 application, but plants treated with GA3 flowered earlier. Cvs Giant Drumhead and Golden Acre did not flower with or without GA3, but some plants of both cvs bolted without flowering. Kale cvs Thousand Headed and Curled Scotch flowered poorly with and without GA3.

The effect of GA3-application on growth and flowering of liatris

The effect of gibberellic acid (GA3) on breaking corm-dormancy, growth and flowering of Liatris spicata L. cultivar ‘Gloriosa’ (gay-feather) was investigated. GA3 could be substituted for the cold requirement in breaking corm-dormancy and promoting earlier flowering, but it did not promote the elongation of the floral stalks. The combined effect of GA3 and cold treatment led to earlier flowering and more inflorescences than either treatment given alone. GA3-application after the corms had received the cold treatment resulted in fewer, but more marketable inflorescences than when the application was done before the cold treatment.

Effects of Genotype and in Vitro Media Composition on Micropropagation of Sugar Cane

The use of plant tissue culture for plant regeneration and propagation on large-scale requires a quantitative approach to optimised conditions associated with vegetative plant regeneration (Lal and Lal, 1990). Numerous factors affect morphogenesis and proliferation rates in micropropagation systems. These include the media composition (Nitsch, 1969; Huang and Murashige, 1977); the nature of donor and explant (Gukasyan et al., 1977; Wang and Ma, 1978); light (Hasegawa et al., 1973); temperature (Carew and Staba, 1965; Seabrook and Cumming, 1978); polarity (Blotch, 1943, Ziv et al., 1970); gas phase (Beasely and Eaks, 1979; Street, 1979), subculture (Hill, 1967; Chen and Galstron, 1967); genotype (Pierik et al., 1974; Pierik and Steegmans, 1976; Seabrook and Cumming, 1978) and season (Robb, 1957; Nitsch and Hughes, 1978). In order to optimise plant regeneration and propagation, a wide range of factors should be investigated.