Gibberellins: Regulators of Plant Height and Seed Germination
• GA levels in plants
are correlated with
stem length.
• Play role in seed
germination, transition
to flowering, and
pollen development.
Figure 20.1 Effect of exogenous GA1 on wild-type and dwarf mutant maize
Figure 20.2 Cabbage can be induced to bolt and flower by applications of GA3
Figure 20.3 Gibberellins induce conebud formation in juvenile conifers
Figure 20.4 Gibberellin induces growth in “Thompson Seedless” grapes
Ch. 20 In-Text Art, pp. 585–586 Gibberellin structures
Figure 20.6 Phenotypes of wild-type and GA-deficient mutants of Arabidopsis
Figure 20.8 Histochemical analysis of Arabidopsis plants containing the GA1 promoter
Figure 20.24 Phenotypes of floral organs of gamyb mutants of rice
Figure 20.9 Phenotypes and genotypes of peas that differ in GA1 content of their vegetative tissue
Figure 20.10 Genetically engineered dwarf wheat plants
Figure 20.11 Impaired seed development in a GA-deficient mutant of pea
Figure 20.12 GA binding properties of GID1 (GA Insensitive Dwarf)
Figure 20.13 Phenotypes of gid1a, gid1b, and gid1c mutants of Arabidopsis (Part 1)
Figure 20.13 Phenotypes of gid1a, gid1b, and gid1c mutants of Arabidopsis (Part 2)
GA receptor mutants exhibit
deficient anther development.
Figure 20.14 Structure of the GA3-GID1a-DELLA complex
Figure 20.15 Model of GA-induced change in the GID1 protein
Figure 20.16 Domain structures of the RGA and GAI repressor proteins
Figure 20.19 Degradation of the DELLA protein by the 26S proteasome
Figure 20.20 Integration of light and GA signaling in Arabidopsis seedlings
Figure 20.17 Opposite effects of two different mutations in the same SLN1 repressor gene
• GA signals the degradation of
negative regulators, e.g. the
degradation of DELLA
proteins.
• Sln1c loss-of-function.
Mutated in GRAS domain;
unable to repress GA
responsive genes even in the
absence of GA.
• Sln1d gain-of-function.
Mutation in DELLA domain
prevents the repressor
protein from being degraded.
Figure 20.21 Structure of barley grain and functions of tissues during germination
Figure 23.3 Precocious germination in the ABA-deficient vivipary 14 mutant of maize
• Ratio of GA:ABA affects
early germination
(vivipary). With high
levels of ABA, seeds
remain dormant.