1. Abscisic acid function in plant development
Seed quality
Stress tolerance
Dormancy
Germination
Biotic stress
response
Stomatal aperture
Gene expression
Development
Abscisic Acid
abscisin II and dormin
ABSCISIC ACID (ABA) controls many plant processes including stress responses, development and reproduction
Guard cell responses
Root growth
Vegetative dehydration responses and osmoprotectants
Seed development
Biotic stress responses
Drought-tolerant plants
Adapted with permission from RIKEN

2. Cytokinins in plant growth
Cytokinins (CKs):
promote cell division in the shoot
delay leaf senescence
regulate nutrient allocation
promote root nodule development
contribute to environmental signaling and pathogen responses
regulate auxin action and distribution
In the 1950s, Folke Skoog’s research group identified a synthetic cytokinin, kinetin
Control
With kinetin
+ CK
+ auxin
and CK
Top row – the plant on the right is silenced in a CK receptor and deficient in root nodule formation. Bottom row: The figure on the left shows a rice variety with slightly increased CK levels leading to increased seed production. In the middle is the classic experiment showing the effects of CK, auxin or both on differentiation of tobacco leaf discs. On the right the AtCKX1 overexpression plant has an increased turnover of CK leading to increased root growth.
Cytokinin was discovered through efforts to identify compounds that increase the growth of plant cells in culture

3. Brassinosteroids
Growth-promoting natural products found at low levels in pollen, seeds, and young vegetative tissues 
Brassinolide was the first isolated brassinosteroid in 1979, when pollen from Brassica napus was shown to promote stem elongation and cell divisions
over 70 BR compounds have been isolated 
Promotion of cell expansion and cell elongation; works with auxin to do so.
It has an unclear role in cell division and cell wall regeneration.
Promotion of vascular differentiation; BR signal transduction has been studied during vascular differentiation.
Is necessary for pollen elongation for pollen tube formation.
Acceleration of senescence in dying tissue cultured cells; delayed senescence in BR mutants supports that this action may be biologically relevant.
Can provide some protection to plants during chilling and drought stress.
BRs appear to be synthesized at their site of action; there is no evidence for long-distance transport of endogenous BRs
BR synthesis is regulated by negative feedback, light and circadian cycles, and interactions with other hormones
BR biosynthesis mutants are dwarfed; a family of cytochrome P450 genes is central to their synthesis