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Published byPhilippa Taylor Modified over 8 years ago
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Behavior = the manner in which a person behaves in reacting to social stimuli or to an inner need or to a combination thereof; OR = good manners OR = an activity of a defined organism, especially observable activity when measurable in terms of quantifiable effects on the environment whether arising from internal or external stimuli OR = anything that an organism does that involves action and response to stimulation OR = the response of an individual, group, or species to the whole range of factors constituting its environment
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Plant Life Cycle: includes stages of dormancy processes of mitosis, cell expansion, differentiation, fertilization (twice!) Plant Development is flexbile: indeterminate, cells toti-potent
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Corn (Zea mays) produces male flowers (tassel) and female flowers (many make up the ear) the plants can ‘self’ or outcross a pollen grain germinating on a style must extend its tube down the length of the style (12 inches or so) and fertilize the embryo at the end of the style in order to make a kernel (ovule) develop
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Once and embryo is formed, it can undergo mitosis (cell division), and differentiation to make all the different cell types, tissues and organs of a plant. This process is called development. Development is regulated at three levels: Genetic – by control of the pattern of gene expression, cells determine which proteins, structures and processes are active Internal signaling – signals include ‘hormones’ other metabolites (sugars, peptides) hydraulic and electric signals External signaling light temperature water nutrient biotic interactions
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Plant ‘hormones’ or growth regulators are active at nM levels. Their activity depends on: 1)rate of synthesis 2)rate of transport to active site 3)receptivity of target/presence of receptor 4) rate of degradation
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Germination: dormancy must be broken seed imbibes water tissues rehydrate embryo releases GA aleuroce cells respond to GA endosperm digested embryo begins to grow root elongation followed by shoot/leaves Seeds are like tiny space ships, launched from their mother into space, packed full of food, primed to germinate if or when they land on suitable substrate.
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Some seeds require light as a cue for germination. The photoreceptor responsible for this sensory process is Phytochrome – red (660 nm)/far red (730 nm) photoreceptor ‘switch’ phytochrome is a protein with enzyme activity (kinase), bound to a chromophore; when the chromophore absorbs R or FR light, it changes the protein conformation, thus activating/inactivating the enzyme
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