BIOL 1120 Lecture Notes - Lecture 20: Stoma, Suberin, Gibberellin

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31 May 2016
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Chapter 40: Sensory Systems in Plants
I. ___________ – biochemicals produced in one part of a plant that have their effect on another part of the same plant (2 categories) (Table
40.1, p. 814-815).
A. Growth Promoting Hormones
1. _________ (Fig. 40.22; p. 817)
a. Promotes _________________
b. Responsible for various tropisms by promoting differential cell elongation.
i. _____________ – growth in response to gravity (Figs. 40.8 & 40.9, on p. 807; Fig. 40.10, p. 808)
Auxin, together with a growth-inhibiting hormone, may play a role in promoting, or inhibiting, growth in
strategic regions.
___________, which are unbound starch grains in the plastids, respond to gravity and may trigger the
redistribution of auxin.
ii. ________________ – growth in response to light (Figs. 40.6, p. 805).
Bending toward the light is caused by elongation of cells (auxin stimulation) on the side of the plant not
exposed to light.
Phototropin 1, a pigment molecule, probably plays a role because of its capacity to absorb blue wavelengths of
light.
ii. ________________ – growth in response to touch (Fig. 40.11, p. 809).
This response is prevalent in climbing vines and in the tendrils that support some plants.
Auxin and ethylene may have roles in the response.
c. Responsible for ________________
i. Auxin produced by the stem apex inhibits the growth of the lateral buds closest to the apex.
ii. The effect decreases progressively down the plant producing a “Chrismas tree” shape.
iii. Removal of the stem apex stimulates lateral bud growth and causes the plant to take on a bushy appearance (Fig. 40.26,
p. 820).
d. __________________________
i. Auxin maintains cells in the abscission zones of fruit and leaf petioles and prevents them from falling off the tree.
ii. If auxin level is decreased, the effects of ethylene will take over and cause fruits and leaves to fall off the tree.
e. Stimulates ______________________
i. Developing seed releases auxin
ii. Auxin promotes expansion of ovary cells causing the ovary to swell and become a fruit
f. Synthetic plant growth regulators or herbicides
i. Indoleacetic acid (IAA) is applied to fruit trees
Promotes uniform flowering
Sets the fruit
Encourages synchronous development of fruit
ii. 2,4-D and 2,4-DB are used as herbicides.
g. Auxin activity results from binding with certain proteins that influence transcription of genes responsible for auxin induced
responses (Fig. 40.23, p. 818).
2.__________ (Fig. 40.30; p. 822)
a. Promote _______________
b. Stimulate buds and seeds to _________________ and resume growth in the spring.
c. Stimulate _______________.
d. Gibberillin activity results from binding with certain proteins that influence transcription of genes responsible for
gibberellin induced responses (Fig. 40.32, p. 822).
3.____________ (Fig. 40.25, p. 820)
a. Stimulate cell division in root and shoot meristems
b. Promotes lateral bud growth (e.g. breaking apical dominance) (Fig. 40.26, p. 820).
c. Maintains leaf longevity
d. Used commercially to prolong the life of stored vegetables and cut flowers.
e. Cytokinin activity results from binding with certain proteins that influence transcription of genes responsible for
cytokinin induced responses.
B. Growth Inhibiting Hormones
1. ________________
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