Chapter 31 - Plant Growth Flashcards
Recall that in many plants, if the shoot apical meristem is removed, axillary buds become active and new lateral branches form. What is this an example of?
apical dominance
A houseplant is growing on your windowsill. Every Sunday, without fail, your roommate turns the plant 180 degrees. When you ask your roommate why she does that, her reply is simply, “I want straight plants.” Does this method produce straight plants?
Yes. Rotating the plant will even out the growth of the plant toward the light by changing where the light hits the plant every week.
Turgor pressure, which causes cells to expand, results in a force applied uniformly to the entire cell wall. How is it that plant cells are often observed to expand in a particular direction—for example, increasing their length but not their girth?
Cellulose molecules individually resist extension, and so the cell wall stretches more readily in directions perpendicular to the dominant orientation of cellulose molecules .
Within the stem of a vascular plant, where would you expect to find the cells that are the MOST mature?
at the base of the stem near the soil
In seed plants, branches grow out from _____, which are meristems that form at the base of each leaf
axillary buds
Flowering is triggered by the production of _____, which triggers the transition from apical meristem to floral meristem identity.
florigen
The highly productive varieties of wheat and rice that were developed in the Green Revolution produce lots of seeds. Given that evolutionary fitness is measured in terms of reproductive success (for which total seed production is a good proxy), why might natural selection have failed to produce these highly productive varieties on its own, without the work of human plant breeders?
Green Revolution crops have reduced stem elongation and thus are poor competitors for sunlight compared to wild plants
A researcher creates a mutant pea plant in which cytokinins are over expressed and gibberellic acid is under expressed. What is the MOST likely phenotype of this mutant pea plant?
The pea plant would be shorter with more branches compared to wild-type plants
Which of the following is NOT one of the major plant hormones?
calcitonin
The condition in which shoot apical meristems suppress the growth of axillary buds is called:
apical dominance
A botanist is studying the growth rings of a redwood tree. She notices that three concentric rings are very thin compared to the surrounding growth rings. What can she deduce from the presence of these thin growth rings?
The tree may have experienced a drought or had limited access to nutrients during that time period
Vascular cambium is one of two lateral meristems; the other is cork cambium. A plant grows in diameter primarily through divisions of the vascular cambium. If you pull a small piece of bark off a tree, and then look at the bark’s inside surface, what tissue are you looking at (ignore any remaining cells of vascular cambium that may be left)?
phloem
Roots are capable of which types of growth?
both primary and secondary growth
Root hairs are MOST abundant:
near the root tip.
The hormone responsible for cell differentiation, particularly xylem and phloem, in the roots is:
auxin.
If you were to dissect a root, the layers from outside to inside would be:
epidermis → cortex → endodermis → phloem → xylem
You have a really leafy houseplant that completely shades the soil in the pot where it is growing. You notice that the tips of some roots are starting to break through the surface of the soil (likely these are new roots growing from the pericycle of an existing root just beneath the surface). If you do nothing, what would you expect to happen to the growth of these roots and why?
The roots will grow downward back into the soil because the statoliths are being redistributed due to gravity and that will change the direction of growth
If a plant stem is exposed to sunlight only on its right side, what happens and why?
The stem will bend to the right, as auxin collects on the LEFT side of the plant, causing cells to elongate
Abscisic acid is produced in the _____ of roots in drying soils and promotes root _____.
root cap; elongation
Phytochrome prevents seeds of some plants from germinating when they are in deep shade by the:
absorption of far-red wavelengths by Pfr.
Gravitropism is a result of:
auxin concentration and the movement of starch-filled organelles called statoliths
A photoreceptor in seeds detects the ratio of red to far-red light, preventing seeds from germinating when:
they are in the shade of another plant.
Short-day plants flower in the _____ leaving enough time to complete seed development before _____.
late summer; winter
Vascular cambium is capable of producing:
secondary xylem and phloem.
