Plant Maintenance
Chapter 19 |
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I. Transportation
A. Transpiration - is the loss of water from the leaves of a plant
1. Water is pulled up from the roots and then evaporated from the stomates of leaves
2. Rate of transportation is regulated by the opening and closing of the stomates
a. guard cells - control the opening of the stomates by osmotic pressure
i. when guard cells become turgid - stomates open
ii. when guard cells lose water - stomates close
B. Transport in xylem
1. Capillary action - the upward movement of a liquid in a tube of narrow diameter - can raise water a few centimeters.
a. adhesion - attractive force between unlike molecules
b. cohesion - attractive force between like molecules
2. Root pressure - osmotic pressure in the root that can hold up a column of water about 1 meter high
3. Transpiration pull - water is held by cohesive forces, pulled up the xylem, and evaporated in the leaves - accounts for the largest movement in tall trees.
C. Translocation- movement of dissolved inorganic and organic materials through a plant - phloem
II. Excretion
A. Gas exchange - through the stomates and lenticels
1. Some of the oxygen and water produced in photosynthesis is used in cellular respiration during the day
2. Some of the carbon dioxide from cellular respiration is used in photosynthesis
B. Nitrogenous wastes
1. stored in vacuoles
2. take in animal wastes
A. Plants are able to synthesize carbohydrates, and proteins from organic and inorganic compounds from material absorbed in the roots with the water
IV. Regulation- accomplished by hormones (regulate plant functions, produced by meristematic tissue)
A. Auxin (IAA - indoleacetic acid)
1. affect the growth of all types of plant tissues (may stimulate or inhibit growth)
2. in growing tips - stimulate differentiation in maturation zone
3. in terminal bud, stimulates growth and inhibits growth in lateral buds
4. tropism - growth response of a plant to a stimulus, results from an uneven distribution of auxins
a. phototropism - bending of a plant stem towards (+) the sun
b. geotropism (+/-) - response to the force of gravity
i. -stems
ii. +roots
c. chemotropism
d. hydrotropism
e. thigmotropism
B. Gibberelins - affect plant growth, fruit development, seeds to sprout
C. Cytokinins - stimulate cell division
D. Ethylene - stimulates flowers, hasten fruit to ripen
E. Abscisic acid - stimulates leaf fall
V. Photoperiodism - response of a plant to changes in the duration of light and dark
A. Long-day plants - requirement for flowering
B. Short-day plants
C. Day neutral plants
New studies show that it is the length of uninterrupted darkness, rather than light that determines flowering.
Biology Trivia
1. Does aspirin come from willow trees? answer
