Relations between cytokinin level, bud development and apical control in Norway spruce, Picea abies

Abstract

In conifers such as Norway spruce, the extent of shoot growth is predetermined by the size and number of embryonal organs of the buds laid down the previous year. As it is known that cytokinins have a key role in bud development a possible hypothesis is that the level of cytokinin in the buds during their formation determines their size and complexity. As a first step to test this hypothesis we compared cytokinin levels in buds of different size of annual shoots from 15‐ to 20‐year‐old trees of Picea abies (L.) Karst. Apical buds from the leaders, and from branches in lower parts of the trees, were collected in April, July and August. The difference in size of the buds and the shoots growing from them was considerable in these three positions. Extracts were purified by immunoaffinity columns, and the retained compounds were separated by high‐performance liquid chromatography (HPLC). Quantification was made by enzyme‐linked immunosorbent assay (ELISA), and the accuracy of this method was checked by measurements with liquid chromatography‐mass spectrometry (LC‐MS) and UV absorption. Zeatin riboside (ZR) was the most abundant cytokinin, but isopentenyladenosine (iPA) was also present in all samples. The large apical bud of the leader contained much higher cytokinin concentrations than the considerably smaller buds from lower positions, and during the period of secondary growth in July, similar relationships were found for annual stem tissue from different positions. The possible role of ZR as a controlling factor in bud development and apical control is discussed. Our conclusion is that the level of zeatin‐type cytokinins appears to play an important role in the establishment of differences in bud size and, thereby, the architecture of the tree crown.

Comparison of endogenous cytokinins, ABA and metabolites during female cone bud differentiation in low and high cone-producing genotypes of lodgepole pine

“…This supports previous studies in which cytokinins were shown to regulate bud differentiation and shoot development in Norway spruce (Bollmark et al 1995;Chen et al 1996) and radiata pine (Zhang et al 2001(Zhang et al , 2003. In angiosperms, cytokinin receptors have different affinities for Z-type and iP-type cytokinins (Spíchal et al 2004;Romanov et al 2006).…”

Lateral Bud and Shoot Removal Affects Leader Growth in Abies nordmanniana

“…the cytokinin concentration in buds is correlated with their size and position, with terminal buds containing more than subterminal buds (Bollmark et al 1995, Chen et al 1996. Gradients in physiological properties between buds in different positions in the crown, a relatively unexplored phenomenon, may explain why the results seem to differ depending on the kind of buds removed.…”

“…The reactions, which surpass the effects of any other debudding studies in conifers known to the authors (Lanner & Connor 1988, Wilson 1992, Wang et al 1997, may be so strong because young trees with relatively few buds were used. Conifer buds are known to contain auxins as well as cytokinins, the concentration of which is rising towards the time of budbreak (Aldén 1971, Qamaruddin et al 1990, Bollmark et al 1995, and removal may have been able to alter considerably the phytohormone balances within the plants. The enhanced growth in length and girth Downloaded by [Australian National University] at 10:57 05 June 2016…”

Cytokinin/Auxin Control of Apical Dominance in Ipomoea nil

“…Grafting studies with the rms4 branching mutant and wildtype plants show that the shoot controls the import of cytokinins from the roots (Beveridge et al 1997). Bollmark et al (1995) have proposed that polarly transported auxin may control bud outgrowth by regulating cytokinin metabolic changes. Auxin might act by controlling the level of active cytokinins (e.g.…”