
TY  - JOUR
A1  - Plummer, Julie A. 
A1  - McChesney, Catherine J. 
A1  - Bell, David T. 
T1  - Germination in Photosensitive Seeds: Does Phytochrome Stimulate Metabolism of GA<emph tye="8">19</emph> and GA<emph tye="8">20</emph> to GA<emph tye="8">1</emph>?
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 1997
VL  - 24
IS  - 3
SP  - 389
EP  - 394
KW  - 
UR  - https://doi.org/10.1071/PP96104 
N2  - The effect of light on gibberellic acid (GA) metabolism was investigated in Asteraceae seeds. White light (80 mmol m-2 s-1 PAR) increased seed germination in Craspedia sp., Erymophyllum ramosum and Rhodanthe chlorocephala subsp. splendida compared with darkness. In these taxa, red light (R, 640 nm, 8 mmol m-2 s-1) stimulated and far red light (FR, 720 nm, 4 mmol m-2 s-1) inhibited germination, indicating the involvement of phytochrome. Paclobutrazol, a GA biosynthesis inhibitor, reduced light-stimulated germination and this was overcome by exogenous GA3. GA3 and GA1 promoted germination in the dark, but GA19 and GA20, which are precursors to GA1, generally did not. GAs were applied to paclobutrazol-treated seeds which were incubated under either R or FR. Very few paclobutrazol-treated seeds germinated without GAs under FR, and exposure to R only marginally improved germination. Application of GA19 or GA20 to paclobutrazol-treated seeds increased germination in Rhodanthe chlorocephala subsp. splendida under R, with no germination under FR. This trend was observed in Craspedia sp., but not in Erymophyllum ramosum or Rhodanthe floribunda. CGA 163&#8242;935, a 3b-hydroxylation inhibitor, and R and FR were used to investigate phytochrome-stimulated conversion of GA19 and GA20 to GA1. It could not be shown that R was required for 3b-hydroxylation in light stimulated germination of these species. 
ER  -

