Endogenous Growth Regulators in Relation to Side Shoot Development in the Tomato

Abstract

SUMMARYA study has been made of the endogenous factors controlling lateral bud initiation and development in the variety Craigella, and two isogenic lines of this variety, Craigella Blind (blbl) and Craigella Lateral Suppressor (isls), in both of which side shoot growth is suppressed to varying degrees. Winter-and summer-sown plants are compared.Lateral Suppressor plants contained higher endogenous levels of auxin in their apices, mature leaves and stems than did normal plants, but lower levels of cytokinins in all parts except the stem, where the levels were similar in both types. The levels of abscisic acid-like substances were consistently higher in the stems of Lateral Suppressor plants than in the corresponding tissue of normal plants, but other plant parts showed a more variable pattern. Lateral Suppressor plants contained higher levels of gibberellin than did normal plants.Blind plants contained higher levels of auxin in the apices and stem than did normal plants, but the levels in mature leaves showed no consistent pattern. Higher levels of abscisic acid-like substances were present in the stem and axillary buds of blind plants than in normal plants, with again a more variable pattern in other plant parts. The levels of cytokinins and gibberellins varied considerably between the two sowing dates.A possible hormonal mechanism of control of axillary bud development is discussed.

Hormones and Young Leaves Control Development of Cotyledonary Buds in Tomato Seedlings

“…Auxins have been shown to be present in the different organs of the tomato (24,25) and particularly in the seedling cotyledons (2). Thus, TIBA treatment could lower the level of auxins in the cotyledonary buds so as to favor their growth by altering the cytokinin to auxin ratio (17).…”

“…Heretofore, studies on the development of the lateral buds of tomato have been concerned primarily with the buds subtended between the first inflorescence ofthe main stem and the cotyledons (3, [22][23][24][25]. There is little information on the inhibition of the cotyledonary axillary buds during the ontogenetic development of the tomato plant.…”

“…The vigorous lateral bud situated immediately below the first main inflorescence was not inhibited by the far red light exposure following the 16-hr photoperiod. Aung (3) indicated that the factors controlling the development of the lateral bud located immediately below the first main inflorescence emanated from the inflorescence itself and from the roots.Heretofore, studies on the development of the lateral buds of tomato have been concerned primarily with the buds subtended between the first inflorescence ofthe main stem and the cotyledons (3, [22][23][24][25]. There is little information on the inhibition of the cotyledonary axillary buds during the ontogenetic development of the tomato plant.…”

“…Tucker (23,24) found that the far red light suppression of the development of lateral buds of tomato was associated with an increase in endogenous levels of auxins and ABA, while stimulation of lateral bud development was associated with increased levels of endogenous gibberellins and cytokinins. The vigorous lateral bud situated immediately below the first main inflorescence was not inhibited by the far red light exposure following the 16-hr photoperiod.…”

Differences in Branch Formation in Indeterminate and Determinate Tomato Types

“…Because emergence of the terminal flower bud occurred earlier than emergence of the axillary bud at the second node, the effect of the terminal flower bud on lateral shoot growth might be stronger than that on the axillary bud in both types of cultivars. Auxin is produced in the apical bud and young expanding leaves in Arabidopsis, Brussels sprouts, pea, and tomato (Tucker, 1976;Thomas, 1983;Zhu and Davis, 1997;Ljung et al, 2001). In the indeterminate cultivars, if the auxin concentration that suppresses lateral shoot elongation decreases temporarily upon ablation of the apical meristem or emergence of the terminal flower bud, the lateral shoot at the second node below the terminal flower bud elongates due to high cytokinin concentrations in the main stem.…”