Length/height. It occurs at root tips and shoot tips.
What are buds?
Regions of growth in the shoot of a plant.
What are hormones
Chemical systems that act at very low concentrations at sites far from they are produced.
What are photoreceptors
Pigments associated with proteins that absorb light.
Plant hormone auxin:
Control direction and arrangement of apical growth; gravitropism, photopropism, apical dominance
Plant hormone gibberellins-
Control the rapidity of speed elongation, seed germination, and fruit maturation
Plant hormone ethylene
Controls fruit ripening and promotes leaf drop
Plant hormone cytokinins
Prevents leave senescence and promotes cell proliferation
Plant hormone absciscic acid.
Inhibits other hormones
Plant hormone florigen
How are the shoots in photoproism
The shoots are positively phototrophic and negatively gavitropic.
How does the signal travel to cause a bend.
The stimulus is initiated at tip of growing stem, travels downward, and causes bend.
Where is a mica barrier inserted?
On the shaded side
what are the steps of phototropism (3)
auxin to shaded end, auxin moves down coleoptile, higher auxin concentration causes rapid growth and elongation on darkr side causing bend towards light
what is gavitropism
roots are positively gavitropic and negatively phototropic
How does cell elongation occur?
It occurs through a change in the structure of the cellulose wall
What happens in apical dominance?
The terminal bud produces auxin and prevents lateral buds from growing.
What happens if shoot cuttings are dipped in auxin solution?
It will develop roots.
Why are gibberellins importan.
They help seed germination and breaking up of winter dormancy
Why is ethylene gas important?
It helps promote leaf drop and food ripening
How is apical hook of eudicot seed maintained?
By asymmetrical production of ethylene
What happens when cytokinins interacts with auxin
They induce proliferation of cultured cells (cell division). In cultures, there is a high cytokinin:auxin ration that promotes shoot formation, and a low ratio promotes root formation
Why is abscisic acid important?
It inhibits other hormones, in doing so, the seeds and water can stay dormant. The stomata closes to prevent water loss and dropping seeds when there is environmental stress (e.g. snow)
What triggers a shoot apical meristem to switch from producing leaves to flowers?
A change in gene expression
What is the study of Arabidopsis?
the study of genes that determine the transition to floral meristems.
What are meristem identity genes
leafy and apetala1 initiate a cascade of gene expression
What do floral organ identity genes do?
They determine whether cells in the floral meristem will be sepals, petals, stamens, or carpels.
What are some external cues that initiate gene expression?
Temp, photoperiod (length day, it helps synchronize flowering in species).
Where is phytochrome found
In the leaf
What is florigen
A diffusible chemical that travels from the leaf to the shoot apical meristem that signals flowering.
Where is florigen made
In the phloem companion cells and travels in the sieve tube elements
What does florigen do in the apical meristem?
It combines with another protein to stimulate transcription of genes that initiate flowering.
What are some things that plants adapt to
Environments, herbivores and pathogens, and low nutrients.
What are some ways that desert plants have adapted?
Water storage, poky, leaves or no leaves, they flower when the rains come, shallow roots.
What does convergent evolution mean
That similar habitats lead to similar adaptations.
When plants are stressed for water, they close stomata to lessen evaporation- decreases co2 concenration in leaf.
What is Rubisco
It is a chemical that can also use O2 as a substrate which lessens or stops glucose production.
What is c4 photosynthesis?
The CO2 is captured and stored as a 4Carbon molecule when stomata are open- in the mesophyll cells. Rubisco concenentraed in bundle sheath cells away from O2- here glucose is made even when stomata is closed.
Similar to c4 but stomata are open at night, stored until morning, and CO2 is released from the 4-carbon compound during the day when stomata are closed.
Defenses against herbivory
Thorns and densely pubescent leaves.
What are trichomes
Hairs that may be sharp and pointed or sticky resulting in physical damage to insects feeding on the plant. Dense hairs may also obscure the epidermis
What is latex and what does it do
It is produced by specialized cells called lactifers that gums up mouth of insects and contains secondary metabolites that may be poisonous.
What does the nerium oleander have to defend itself against predators
High levels of alkaloids and cardiac glycosides.
How do venus fly traps open/close
By changes in turgor pressure
How do plants adapt to low soil nutrients
Legumes have symbiotic relationships with nitrogen-fixing bacteria for supply.