Studies on Flower Initiation in Black Currant: II. Photoperiodic Induction of Flowering

The effects of three levels of a widely used tea nursery fertilizer mixture containing ?, ?,ρ?, Mg and SO4 and hormones on growth and apical dominance were studied using free-growing plants of two vigorous TRI clones.

At the highest level of fertilizer (F2) the plants showed earlier bud-break and an increase in the number and duration of active phases, with a reduction of the dormant phases. These resulted in more growth and dry matter accumulation and in more lateral shoot growth than was obtained with lower levels of fertilizer (FO and Fl). Leaf production on both main and side shoots was increased at the higher levels of nutrition. The results showed that vigorous clones may benefit from higher levels of fertilizer application than the presently recommended rates.

Gibberellic acid (200 ppm) alone or with benzyl adenine (25 ppm) tended to cause earlier bud-break at FO and Fl but not at F2. The percentage bud-break obtained at F2 was, however, similar to that obtained at FO and Fl with the above hormones. GA₃ or GA₃+BA also increased the height of the plant, the response persisting for at least a month starting a fortnight from the first application. Neither BA (25 ppm) applied alone nor IAA (200 ppm) stimulated bud-break, but IAA increased the height of the plants at the higher levels of fertilizer used. There was an interaction between fertilizer and hormones during the period when the hormones were effective in increasing height.

A relationship was found between the growth of the shoots, natural and induced, and that of the roots. The active plant had about twice the amount of feeder roots as the dormant plant.