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Title: Photomorphogenesis of the root system in developing sunflower seedlings: a role for sucrose
Abstract

The domestic sunflower (Helianthus annuusL. cv. ‘Giganteus’) has been used since the 19th century as a model plant for the study of seedling development in darkness and white light (WL) (scoto‐versusphotomorphogenesis). However, most pertinent studies have focused on the developmental patterns of the hypocotyl and cotyledons, whereas the root system has been largely ignored.

In this study, we analysed entire sunflower seedlings (root and shoot) and quantified organ development in the above‐ and belowground parts of the organism under natural (non‐sterile) conditions.

We document that seedlings, raised in moist vermiculite, are covered with methylobacteria, microbes that are known to promote root development inArabidopsis. Quantitative data revealed that during photomorphogenesis inWL, the root system expands by 90%, whereas stem elongation is inhibited, and hook opening/cotyledon expansion occurs. Root morphogenesis may be mediatedviaimported sucrose provided by the green, photosynthetically active cotyledons. This hypothesis is supported by the documented effect of sucrose on the induction of lateral root initials in sunflower cuttings. Under these experimental conditions, phytohormones (auxin, cytokinin, brassinolide) exerted little effect on root and cotyledon expansion, and no hormone‐induced initiation of lateral roots was observed.

It is concluded that sucrose not only acts as an energy source to fuel cell metabolism but is also a shoot‐derived signalling molecule that triggers root morphogenesis.

 
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NSF-PAR ID:
10461176
Author(s) / Creator(s):
 ;  ;
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
Plant Biology
Volume:
21
Issue:
4
ISSN:
1435-8603
Page Range / eLocation ID:
p. 627-633
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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