Abstract

By application of a recently developed method allowing analysis of gibberellins (GAs) in mg amounts of tissue, the effect of photoperiod on levels of GAs in shoot tips of individual seedlings of the woody species Salix pentandra was studied. In elongating long day-grown seedlings, maximum levels of GA(1) were found 5-20 mm below the apex, approximately twice the levels in other segments. After exposure of plants to 5 or 15 short days, the levels of GA(1) were about 50% lower within this specific region of the stem, as compared with seedlings grown under long days. Short day-induced cessation of shoot elongation also correlated with overall declines in the levels of GA(53), GA(19), GA(20) and GA(8). Within each photoperiodic treatment the levels of these GAs were generally relatively similar throughout the upper 35 mm of stems. No differences in internode lengths or in lengths of pith or epidermal cells were found in plants grown under long days compared with those exposed to 5 short days. In both cases, cells in mitosis were observed in the subapical stem tissues of shoot tips. After 15 short days, stem elongation was completed, and dividing cells were generally not found in the subapical part of the stem. However, short day exposure did not prevent elongation of internodes and cells differentiated before the treatment was started. Thus, the localised decrease in level of GA(1) in shoot tips under short days precedes the morphological and anatomical changes connected with the short day-induced cessation of elongation growth. This supports the hypothesised role for GA(1) in photoperiodic control of shoot elongation in S. pentandra.

Keywords

gibberellins; photoperiod; Salix pentandra; shoot elongation

Published in

Physiologia Plantarum
1995, Volume: 95, number: 4, pages: 627-632
Publisher: MUNKSGAARD INT PUBL LTD

SLU Authors

• Moritz, Thomas

  • Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Botany


Publication identifier

DOI: https://doi.org/10.1111/j.1399-3054.1995.tb05532.x

Permanent link to this page (URI)

https://res.slu.se/id/publ/42898