Flower initiation and development of Protea cv. Carnival

[摘要] ENGLISH ABSTRACT: Advancement of the flowering time of Protea cv. Carnival by approximately three months,without compromising the product quality, was achieved by the application of 6-benzyladenine-containing plant growth regulators to three-flush shoots in autumn. Thisearlier flowering time coincides favourably with the prime European marketing period(November-January). The percentage three-flush shoots initiating an inflorescencefollowing the brush application of the 6-benzyladenine (BA)-containing regulators, ABG-3062 (active ingredient: BA 2% w/w) and Accel® (active ingredients: BA 1.8% w/w;gibberellins A4A7 0.18% w/w) on dormant terminal buds, increased with later applicationdates and flowering percentages as high as 90% was achieved. No inflorescences wereinitiated on flushes induced by Promalin® (active ingredients: BA 1.8% w/w; gibberellinsA4A7 1.8% w/w).Phenological phase progression of green point, flush expansion and inflorescencedevelopment of 'Carnival' shoots as induced by BA was calculated to have base temperaturesof 8°C, 6°C and 1°C respectively.The days required from application of the BA-containing growth regulator until green pointstage increased progressively over the six consecutive treatment dates in autumn (14 March -22 May 2003). In contrast, the days required to complete inflorescence developmentdecreased with each successive treatment date. The days required between the respectivestages were mostly negatively correlated with temperature, except for the phase 'green pointto flush expansion', where the relationship was unclear. For three-flush shoots of eight-yearold plants, between 13-57, 39-65 and 121-177 days were required to reach green point, to achieve full flush expansion following green point and to complete inflorescence after flushexpansion respectively.BA application enhanced budbreak in most dormant shoots, irrespective of plant age, BAconcentration, decreasing temperature over time or shoot characteristics. However, twoflushshoots treated in late May had low budbreak and hence low flowering percentages.Shoots varied considerably in their responsiveness to BA treatments. BA application(500mg·L-1) as MaxCelTM (active ingredients: BA 1.9% w/w) to terminal buds alone ofmature three-flush shoots from less vigorous growing plants resulted in the highest floweringpercentages. Applications were most effective when applied to the terminal bud in thedormant state or up to the 'green point' stage. Shoot characteristics such as flush length, leafarea, shoot dry mass, number and proximity of the leaves to the terminal bud were allpositively correlated with the propensity of shoots to initiate inflorescence under BAinduction. Terminal flush intercalation shoot diameter (>7mm) was identified as the mostimportant variable influencing the likeliness of flowering and can effectively serve as a nondestructiveestimation of a shoot's propensity to flower.The presence of developing inflorescences or possible floral inhibiting factors derived fromthe previous flowering season is suggested to be inhibitory to inflorescence initiationfollowing BA application. Synchronisation of shoot growth by pruning plants in late winterappears to be an essential step to ensure high percentages inflorescence initiation with BAtreatment the following autumn. The use of BA as a management tool to control floweringtimes in Protea for better market opportunities is shown to hold considerable commercialpotential.

[发布机构] Stellenbosch University