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John Clemens and R. Hugh Morton

Containerized plants of Heliconia psittacorum L.f. × H. spathocircinata Aristeguieta `Golden Torch' were grown in a greenhouse for 8 months from early summer to winter under selected combinations of N, P, and K. Fertilizer rates ranged from zero to rates that exceeded those reported in the literature by 50% to 100%. Biomass variables (vegetative and inflorescence dry weight, and leaf area) were predicted to be maximized at high N and high N to P, and N to K ratios corresponding to N-P-K application rates of 1.2, 0.5, and 0.6 kg·m-3, respectively (≈2:1:1). However, the number of shoots and flowers produced per rhizome were maximal at lower N to K ratios (1:1). Flower yield could therefore be optimized with appropriate fertilization, provided attention was paid to the N to K ratio so that the size of plants and their flowers was not compromised by efforts to increase shoot and flower number. The heavier the rhizome planted, the shorter the time for shoot emergence and flowering to occur, and the greater the number of flowers harvested. However, rhizome weight had no effect on number of shoots to emerge. The probability of shoots flowering declined markedly with order of shoot emergence, although this could be increased with appropriate mineral nutrition. The maximum number of leaves subtending the inflorescence (seven) was obtained at high N and P rates. Flower production was probably limited by declining solar radiation in autumn, and by within-plant competition for rooting space.

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Allan B. Woolf, John Clemens, and Julie A. Plummer

Six concentrations of ethephon were applied to plants of `Donation' and `Anticipation' Camellia (L.) at two times (late summer and autumn) and three times (late summer, autumn, and midwinter) of the year, respectively. Abscission of leaves and floral and vegetative buds was determined. Sensitivity to ethephon varied markedly among plant organs. Greater sensitivity of floral buds indicated that ethephon could be used to selectively remove these with minimal abscission of other plant organs. Proportion of abscised organs varied with cultivar and time of application. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).

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John Clemens, Ewen A. Cameron, and Richard C. Funt

Calla (Zantedeschia Spreng.) growers were studied as members of an expanding sector in the New Zealand floricultural industry. The calla sector is characterized by diverse-size firms scattered throughout the two main islands of New Zealand. Growers differ in their skill and experience with calla production. Problems are both grower-specific (e.g., control of diseases, postharvest disorders) and sector-wide. Examples of the latter include the prioritizing and funding research, interacting with science organizations and planning sector marketing strategy. Both sets of problems have been exacerbated by the progressive withdrawal of research and extension support services traditionally provided by government agencies. There is competition between the floriculture industry and calla sector-based grower organizations. The leadership role of a strong grower organization, in this case the New Zealand Calla Council (NZCC), is seen as an essential forum for growers, and as the link between growers, exporter organizations, scientists and central government. Good communications between the industry organization and growers is essential to identify and prioritizeproblems and to transfer information to individual growers through workshops, newsletters and manuals. To maintain its effectiveness, the NZCC does not satisfy the needs of smaller growers at the expense of the larger, influential growers. Rather, it seeks to the benefit the latter by upgrading the skill level of the industry, and by undertaking tasks too large for any individual business.

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Allan B. Woolf, John Clemens, and Julie A. Plummer

The influence of temperature and leaf maturity on ethephon-promoted abscission was examined by simultaneously applying either ethylene (10.5 μl·liter-1) or ethephon (0 to 4 ml·liter-1) to potted Camellia plants at four constant temperatures (10 to 30C). The abscission rate (time to 50% abscission) and extent of abscission of leaves, and vegetative and floral buds was measured. Increased temperature promoted the rate and extent of ethephon-promoted abscission and increased ethylene-promoted abscission rate of all organs of Camelliu. Lower temperatures reduced the abscission rate after ethephon application more than that following ethylene application. Sensitivity to ethephon was greater for leaves on newly extending shoots, although once shoot elongation and leaf expansion had ceased, leaves became less sensitive. Ethephon sensitivity increased progressively with maturation over the following 2 years. Optimal thinning of floral buds. at low temperatures required high ethephon concentrations, while at high temperatures, low ethephon concentrations were optimal. The influence on abscission of the time of year when ethephon was applied, is suggested to be due to tissue maturity, which affects tissue ethylene sensitivity, and temperature, which affects ethylene release from ethephon and tissue response to ethylene. Chemical name used: (2-chloroethyl) phosphoric acid (ethephon).