Ch 7 Review Questions

What roots can produce shoot buds that can act as new plants?

Willows, sorrel, and other plants spread horizontally, they produce shoot buds that grow out and act as new plants.

What does the root cap do?

It protects the root apical meristem. It evolved because the root meristem has to penetrate through soil.

What roots act as holdfasts?

Ivy and other vines have modified roots that act as holdfasts, clinging to rock or brick.

Plants that have fibrous root system

Most monocots and some eudicots. Gladiolus (sword lily) Associated with rhizomes and stolons

Are there any mature cells in the zone of elongation?

None of the cells is mature.

What would happen to root hairs if they formed in the zone of elongation?

Root hairs form only in a part of the root that is not elongating; otherwise, they would be shorn off. Needed for surface are expansion and ions extraction. Probably not needed in water or air.

What is an adventitious root?

Root primordia, which are initiated in the stem tissue. Roots that do not arise on pre-existing roots and are not radicles. Adventitious roots increase the absorptive and transport capacities of the root system.

What's the diameter of a root and a root hair?

Roots are 100um in diameter and root hairs are 10um in diameter.

What are the three functions of roots?

1. Anchoring the plant firmly to a substrate 2. Absorbing water and minerals 3. Producing hormones

How many lateral roots do rye have? with how much root length and surface area?

13 million lateral roots with 500 km of root length and a surface area of 200m^2.

What is the shape of the endodermis? What are Casparian strips and on which cells are they located?

Cylinder. It's what connects the endodermis, like cement on a chimney. Located in walls of endodermis cells.

What does the radicle develop into in monocots?

Into adventitious roots

What does the radicle develop into in eudicots?

Into taproots

Why do plants have highly branched root system instead of just one long root?

Because roots must have an enormous absorptive surface; in order for a single unbranded root to have sufficient surface area, it would have to be hundreds of meters long, which would make conduction impossible.

Plants that that have taproot system

Carrots, beets, turnips, sweet potatoes, cassava. Associated with nutrient storage in biennial species.

Which part of the root detects gravity with which organelles?

Cells are small and meristemic when first formed at the base of the root cap, but as they are pushed forward, they develop dense starch grains and their endoplasmic reticulum becomes displaced to the forward end of the cell. These cells detect gravity because their dense starch grains settle to the lower side of the cell.

What roots store carbohydrate during winter?

Fleshy taproots, such as those of carrots, beets, and radishes, are the plant's main site of carbohydrate storage during winter.

What are the four diffusion paths that a molecule might follow as it travels through the root epidermis and cortex and what happens at the endodermis?

Happens at root of maturation/Root hair zone. Apoplastic transport which is by diffusion through the walls and intercellular spaces. By absorption into the cytoplasm of a cortical cell. Symplastic transport which is transferal from cell to cell, probably through plasmodesmata. Oxygen diffusion throughout the root from soil or stem allowed by cortical intercellular spaces as an aerenchyma. Because the endodermis is waterproof due to encrusted lignin and suberin.

If a bamboo rhizome grows 100 feet underground and then sends up an aerial branch, where does that branch get its water- from the roots 100 feet away or from adventitious roots right at its base?

If a plant can produce adventitious roots, the bottleneck of the monocot stem does not matter. New roots originate near the aerial shoots and conduct directly to them, and little or no long-distance conduction occurs in the rhizome. No part of the monocot stem needs to conduct all of the water from all the roots to all the leaves and flowers, as does the trunk of a woody plant.

What roots grow out of the trunk and harden into spines?

In the palms Crysophila and Mauritia, roots grow out of the trunk and then harden into sharp spines.

Would there be any fully differentiated epidermis cells or vascular tissue in the zone of elongation?

Not fully differentiated but they do begin to do so at this zone. The outermost cells are protoderm and differentiate into epidermis. In the center is provascular tissue, cells that develop into xylem and primary phloem. Protoxylem and protophloem, which form earliest, are closer to the meristem.

What roots attack other plants and draw water and nutrients out of them?

Parasitic flowering plants (mistletoe and dodder) attack other plants and draw water and nutrients out of them through modified roots.

What is the name of the embryonic root?

Radicle

What are the two types of root systems?

Taproot systems and fibrous or adventitious root system.

The mitotically inactive central region of the root apical meristem that are not synthesizing DNA is called what and what it is a reserve for?

The quiescent center. They are a reserve of healthy cells.

What does the radicle do after germination in monocots?

The radicle dies during or immediately after germination; root primordia at the base of the radicle grow out and form the first stages of the fibrous root system.

What are the only parts of the root that become longer?

The root apical meristem and the zone of elongation, a region only a few millimeters long within which the cells undergo division and expansion.