Hormones Flashcards
(15 cards)
What are hormones?
Chemical compounds made in one part of an organism that control activity in another part of the same organism
What are the 5 types of hormomes?
Which are situmalators and which are inhibitors?
Auxins
Cytokinins
Gibberellin
Ethylene
Abscisic Acid (ABA)
Auxins
- Stimulate growth by elongating the cells of a plant
-Initiate leaf formation by encouraging cell division
-Produced in the apical meristem, roots, young leaves, buds, and any other place with rapidly growing tissue
-Initiate fruit development after pollination and inhibit fruit from ripening in many fruits (not all)
-Auxins can cause parthenocarpy- When fruit is formed with no fertilization of the egg
Synthetic auxins
Act as weed killers by causing growth to be so fast plant is unable to keep up and obtain nutrients
Auxins in apical meristem
Auxins in the apical meristem can cause apical dominance in plants, when a plant grows upwards with little to no side branches. Removing auxins in apical meristems causes growth promotion for side branches. good because it can produce more leaves and increase surface area for photosynthesis, but too many side branches lead to a bushy and uneven plant
Auxins inhibit..
Inhibit absscion (falling of plant) of young leaves and fruits
As the plant gets older, auxin levels decrease
What happens if there is no auxins?
Control things like
-cell elongation
–> No cell elongation, no root and stem growth. Cells will divide, but cells won’t elongate, so plants will have stunted growth
-Phototropism
–> The plant stem won’t grow towards the light. The plant is unable to do photosynthesis and will die
-fruit development
—> Fruits will not form, and fruit is important cause it protects and disperses the dormant seeds
-prevents abscission of young leaves and fruit
–> The plant might lose leaves too early, which it needs for photosynthesis to obtain food and energy, especially in growing plants
–> Immature fruit may fall off before seeds are ready (seeds may not be able to grow strong, form seed coat, get food reserves ready)
cytokensis
-Promote cell division and differentiation (plant stem cells)
-Stimulate production of proteins required for mitosis and cytokinesis
-Helps delay against of leaves and fruits
what happens if no cytokeninis?
-No cell division
–> plants’ roots, stems, and young leaves will grow poorly
-No cell differentiation
–>no specialized cells will cause an incomplete plant (no xylem, no phloem, no guard cells)
-No proteins for mitosis, then poor growth
-Fruits and leaves age early means leaves will yellow faster (less chlorophyll) and fruits will ripen faster
Gibrellelins
- Produced in apical meristem
-Many different kinds
-once released in the plant stops dormancy and initiates dormancy
-transported in vascular tissue
-reverses genetic dwarfism by turning on the gene for cell division
-promotes growth of taller and stronger plants
-promotes growth in flowering plants
-used in commercial fruits to make them larger
ethylene
-only a gaseous hormone
–> released in the air as a gas, and ripening fruit will cause other fruit to ripen as well
- Found in the plant tissue of leaves and fruits
-Transported by phloem
- weakens cell walls of unripened fruit and breaks down complex carbs into simple sugars
-Promotes the aging of leaves and flowers and ripens fruit
–> Fruits’ chloroplast breaks down as it ripens, which is why it changes colors
No ethylene
- Fruit stays unripe, sour and green
-Cell walls stay tough in fruits, and starch is not broken down to sugars, and the fruit is not sweet
-No aging of plant leaves or fruit
–> delays abssicon ,and causes waste of energy
Absisic acid (ABA)
-Made in apical meristem, fruits, and root caps
-Inhibits the growth of buds
-Promotes seed dormancy
Controls the opening and closing of the stomata
promotes absorption of fruits and leaves
blocks the action of growth-promoting hormones
No ABA?
- Controls the opening and closing of stomata
–> no aba then it won’t tell stomata to close during drought to preserve water
–> The plant might lose too much water and die
-Promotes seed dormancy
–>stops seeds and buds from growing too early
–> make sure growth happens when conditions are favorable
-balance hormones
–> The plant will overgrow and waste energy - Helps plant sheds leaves and fruits that are old
Abssion
-natrual process where leaves and fruits fall of as they age
- good becasue transpitartion is reduced and in times like winter or drought helps plant survive by preserivng water
-instead of mauinitny old and damsged tissue allows or new leaves and flower buds to grow
