Lab 5 Flashcards
what are the primary functions of roots?
anchor the plant in the soil and absorb water and essential minerals
what does the root system of a plant consist of?
a primary roots (which develops from the radicle of the embryo), which gives rise to lateral roots. each root has a root apical meristem, protected by a root cap at its tip
what is the tap root system?
usually found in eudicots and conifers, has a large dominant primary root and several lateral roots (food storage is often important in tap roots)
what is the fibrous root system?
common in monocots, has many roots of equal size and no detectable primary root (well adapted for anchorage)
what do the cells of the root cap produce?
mucigel, which contains sugars, vitamins, amino acids, and enzymes
what is the function of mucigel?
lubricates the root for its passage through the soil and helps prevent water loss from the soil
what are statoliths?
specialized amyloplasts in the root cap that move in response to gravity
what are the five important functions that roots serve in the plant body?
- anchorage
- absorption
- storage
- transport
- growth
what are adventitious roots?
roots that develop from stems or leaves rather than from other roots
what are aerial roots?
almost always adventitious, produced above ground, and can be specialized for a variety of functions
what are haustorial roots?
roots that glue themselves to the stems of trees and are specialized to penetrate the xylem of their host for a water source (mistletoe)
what are aerating roots or pneumatophores?
roots that project up out of the water or wet soil for aeration
what are propagative roots?
roots that form shoot buds along their length from which new shoots can grow (asexual reproduction) (canada thistle and trembling aspen)
what are storage roots?
roots modified to store large amounts of food or water (carrots, radishes, etc..)
what are root nodules?
enlarged structures that form as a result of bacteria invading root hairs and growing in the cortex tissue of the root (found in legumes)
what does the cortex (ground tissue in roots) consist of?
- exodermis: a thin layer of parenchyma cells that contain suberin
- storage parenchyma: a thick layer of large diameter, thin-walled parenchyma cells packed with starch grains. intercellular spaces are numerous
- endodermis: thick-walled cell layer that forms the innermost layer of the cortex and separates the cortex from the central vascular cylinder (the stele)
what is the function of the casperian strip?
prevents the passage of water from the cortex to the stele through the cell wall area
what is the vascular cylinder (stele) composed of?
vascular tissue (xylem and phloem) and a layer of associated ground tissue called the pericycle
what is the pericycle?
a meristematic layer of ground tissue in the stele which can give rise to lateral roots
what is the pith?
a central region of ground tissue in monocot roots that is typically composed of parenchyma
