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TTU / Plant and soil science / PSS 1321 / What are the plant hormones and their functions?

What are the plant hormones and their functions?

What are the plant hormones and their functions?


i Plant hormones  

What are the plant hormones and their functions?

a Auxins

i Adventitious roots initiation  

ii Auxin concentration affects root, bud, and stem growth variably b Cytokinins

i Zeatin is the most common cytokinin in plants

ii Site of biosynthesis:

1 Primarily in root tips

ii Chemical response is dose dependent  

iii Functions:

1 To induce shoot growth in plant tissue culture  

ii (high cytokinin/low auxin=shoot growth)

iii (Low cytokinin/high auxin=root growth)

b Ethylene

i Gaseous hormone

ii Site of biosynthesis:

1 Most tissues/cells in response to stress (especially during  

senescence to ripening)

What is the function of cytokinins?

b Abscisic acid (ABA) If you want to learn more check out What is the multi-variable chain rule?

i Site of biosynthesis:

1 Mature leaves, especially in response to water stress

ii Stress hormone for plants

iii Water stress causes an increase in ABA synthesis and it causes the  stomata to close

iv ((AVP1 stimulates auxin polar transport which stimulates root  growth))

b Gibberellins

i Site of biosynthesis:

1 Young tissues of shoots and in developing seeds

ii They elongate shoots

iii Cell expansion

iv Seed germination

v A plants response to a particular hormone will be species dependent  ii Plant growth regulators We also discuss several other topics like What is the considerable number of male witches?

a Human made synthetic hormones

ii Plant chemicals

What is the use of ethylene?

a Primary vs secondary metabolites (biochemicals)

i Primary

1 Directly involved in normal growth, development, and  


2 Occur in all plant cells We also discuss several other topics like What is the arterial system?

3 Three classes:

a Carbohydrates (sugars)

i Simple organic compounds

ii C, H, O (with H and O in 2:1 ratio)

iii Storage and transport of energy (e.g., glucose,  

sucrose, fructose)

iv Structural components of cells (e.g., cellulose, chitin)  

and in RNA/DNA (ribose, deoxyribose)

v Plants are carbohydrate-rich organisms

b Lipids

i Energy storage - triglycerides in seeds

ii Structural lipids - membrane lipids (phospholipids)

iii Cuticular lipids (waxes and cutin make up the cuticle) iv You get the most energy from a fat molecule  

b Proteins  

i Have a C-N (Carbon - nitrogen) backbone

ii All enzymes are proteins (= catalysts that carry out all  of the chemical reactions involved in plant growth)

iii Nucleic acids (DNA, RNA) are translated into amino  acids and then into proteins

iv Transcription- the synthesis of RNA under the direction  of DNA

v Translation - the actual synthesis…??? If you want to learn more check out John bowlby’s attachment theory was based on which studies?

vi Are chains of amino acids

ii Secondary  

1 Not directly involved in normal growth, development, and  reproduction

2 Occur usually only in special, differentiated cells

3 Are species-specific, not all plant species produce all secondary  metabolites  

4 Absence of secondary metabolites does not result in immediate  death, but may impair long-term survivability, fecundity, or  other functions

5 Many of these are highly toxic and are often stored in specific  vesicles or in the vacuole

6 Important in defense against herbivory

7 Three major categories:

a Alkaloids

i A group of nitrogen-containing compounds

ii Many are poisonous to humans in small doses  We also discuss several other topics like How many atria are in the human heart?


iii Morphine, atropine, and cocaine are (were) used in  medicine

iv Plant defense  

b Phenols

i Species-specific production in plants

ii Astringent taste (slightly acidic)

iii Tannis, flavonoids (anthocyanins)

iv Plant defense, attracting pollinators (anthocyanins),  and seed dispersal (flavor)

b Terpenes  

i The largest class of secondary metabolites -- over  

30,000 have been described

ii Essential 'oils' (e.g. flavor, fragrance) cartenoids  

(yellow and orange pigments)

iii Plant growth, plant defense (e.g. resin, latex)

iv Plants talk to eachother apparently (watch out vegans) v Fungal organsims are more of a physical  

communication rather than a gaseous communications

vi If you don’t know that the bluebonnet is the texas  

state flower either you're not from texas or you're a  

dumbass. Also if you didn’t know that you cant pick  

them you're a dumbass.

ii Plant genetics  If you want to learn more check out What is the component of the basic product consisting of the fundamental benefits?

a Genetics is the study of genes.

b To explore the characteristics that are inherited

c To understand how the characteristics are transmitted from one  generation to another generation.

d Why study genetics of plants?

i To meet the food, clothing, shelter, and other plant-related demands  of a growing population.

ii Genetic modification of crops: quality and quantity

iii Insect and disease resistant cultivars  

iv Enviromental stress resistant cultivars (against stress, salt, drought)  v To conserve natural genetic resources from:

1 Over-exploitation

2 Changing environmental conditions

ii To understand evolutionary processes  

1 What causes a new species to evolve  

2 What is the level of genetic differences among individuals,  species, families,… and kingdoms.

b Plant genetic resources

i Basis of global food security

ii Consists of diversity of seeds and planting material of traditional  varieties and modern cultivars, crop wild relatives, and other wild  plant species

iii Used as food, feed, fiber, clothing, shelter, aesthetics, and energy  b Cultivated plant species  

i Less than 10% (~35,000) of all plant species are cultivated ii ~30 crops provide 95% of human food energy needs

iii Four of which (rice, wheat, maize, potato) are responsible for more  than 60% of our energy intake

iv For global food security, it will be crucial to maintain a high genetic  diversity within these crops to cope with changing environmental  stresses

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