Articles
Curvature development in vegetative Leucospermum Soleil and Succession II shoots in response to gravity and a consistent force
Article number
1347_14
Pages
93 – 100
Language
English
Abstract
The value of Leucospermum cut flowers, an important international floricultural crop indigenous to South Africa, is largely determined by shoot length and stem straightness. Leucospermum is known to be floriferous shrubs where some cultivars exhibit a spreading growth habit while others tend to grow upright.
The process that determines whether a shoot will remain straight or be curved is not well-studied in cut flowers and not at all explored in Leucospermum. To explain observed curvatures that develop during the development of vegetative stems, it was proposed that persistent winds in early summer amidst the vegetative growth season might influence Leucospermum shoot growth behavior, as wind acts as a load similar to gravity, with both interacting to induce bending of shoots.
The aim of this study was therefore to explore the nature of shoot curvatures in Leucospermum by comparing a cultivar with a spreading growth habit, Soleil, with an upright growing cultivar, Succession II. Shoot reaction to gravity when placed at 45° or its response to an externally applied load were compared with respect to the resulting radii of curvature and its associated deviation length of the stem.
The radii of the curvatures exhibited by Soleil shoots were lower, indicating a sharper bend, compared with curvature radii recorded on Succession II shoots.
This implicated a greater propensity for curvatures to occur in Soleil than in Succession II shoots.
Cultivar differences with regard to the inherent rate of lignification or arrangement of lignin is suggested.
This study provides a first report on the nature and causes of shoot curvatures in Leucospermum, with the aim to timeously advise breeders and producers to better manipulate vegetative growth in Leucospermum cultivars to achieve more marketable shoots for greater profitability.
The process that determines whether a shoot will remain straight or be curved is not well-studied in cut flowers and not at all explored in Leucospermum. To explain observed curvatures that develop during the development of vegetative stems, it was proposed that persistent winds in early summer amidst the vegetative growth season might influence Leucospermum shoot growth behavior, as wind acts as a load similar to gravity, with both interacting to induce bending of shoots.
The aim of this study was therefore to explore the nature of shoot curvatures in Leucospermum by comparing a cultivar with a spreading growth habit, Soleil, with an upright growing cultivar, Succession II. Shoot reaction to gravity when placed at 45° or its response to an externally applied load were compared with respect to the resulting radii of curvature and its associated deviation length of the stem.
The radii of the curvatures exhibited by Soleil shoots were lower, indicating a sharper bend, compared with curvature radii recorded on Succession II shoots.
This implicated a greater propensity for curvatures to occur in Soleil than in Succession II shoots.
Cultivar differences with regard to the inherent rate of lignification or arrangement of lignin is suggested.
This study provides a first report on the nature and causes of shoot curvatures in Leucospermum, with the aim to timeously advise breeders and producers to better manipulate vegetative growth in Leucospermum cultivars to achieve more marketable shoots for greater profitability.
Publication
Authors
E.-L. Louw, G. Jacobs, E.W. Hoffman
Keywords
growth habit, lignification, negative gravitropism, pincushion, Proteaceae, wind
Online Articles (21)