ROOT AND MINERAL NUTRITION Flashcards
branching underground root system are often more ______ than the aerial parts
extensive
2 main functions of roots
- anchors a plant in the soil
- absorbs needed water and minerals
two types of root system
TAPROOT SYSTEM
FIBROUS ROOT SYSTEM
differentiate taproot system from fibrous root system
taproot system consists of one main root, then many lateral roots branch out of the taproot. the main root come from the seedling’s embryonic root or radicle (characteristic of eudicots and gymnosperms)
fibrous root system consists of many roots of similar size, with lateral roots branching off these roots. the main roots arise from the stem itself
(characteristic of monocots)
the taproot system consists of one main root formed from the seedling’s what?
embryonic root (RADICLE)
these cells secrete lubricating polysaccharide to reduce friction
ROOT CAP CELLS
these cells help orient the root so that it grows downward
ROOT CAP CELLS
short-lived tubular extensions (trichromes) of epidermal cells located just behind the growing root tip
ROOT HAIRS
the absorptive capacity increasing by surface area is caused by these trichromes
ROOT HAIRS
a single layer of protective ______ covers roots
epidermis
root hairs and no cuticle increase _________
absorption
most water that enters the root moves along what
cell walls made of cellulose
the _______ composes most of the root
cortex
roots usually lack supporting _________ cells, but may develop some __________ as they age
collenchyma; sclerenchyma
the primary function of root cortex is _________
starch storage
in a root cortex, ______________ provide a pathway for water intake and allow aeration of the root
large intercellular spaces
in a root cortex, water and dissolved minerals move along two pathways:
SIMPLEST PATHWAY: living cells interconnected by plasmodesmata
APOPLAST PATHWAY: uses cell walls and intercellular spaces
the ___________ regulates movement of water and minerals that enter the xylem
ENDODERMIS
_________ cells fit tightly against one another – each cell has a _____________ on its radial and transverse walls that contains a waterproof material (_________)
endodermal; CASPARIAN STRIP; suberin
a band of cell wall material deposited in the radial and transverse walls of the endodermis (the cell walls are mostly made of suberin instead of lignin)
CASPARIAN STRIP
these prevent water and minerals from continuing to move passively along the cell walls
CASPARIAN STRIP
these are at the center of a eudicot primary root
STELE
this is inside the endodermis; consists of a single layer of parenchyma cells that give rise to lateral meristems/roots
PERICYCLE
a lateral root pushes through what before entering the soil
several layers of root tissue
the centermost tissue of the stele; often has two or more extensions
XYLEM
these are the patches between the xylem arms in the stele
PHLOEM
these conduct dissolved sucrose in the roots
SIEVE TUBE ELEMENTS
is sandwiched between the xylem and phloem in the stele
VASCULAR CAMBIUM
how does monocot roots differ from eudicot roots
the phloem and xylem are in separate, alternating bundles arranged around the central pith of parenchyma cells;
no vascular cambium exists in monocot roots
___________ and ____________ have primary growth at apical meristems and secondary growths at lateral meristems
GYMNOSPERMS and WOODY EUDICOTS
woody plants have roots with ___________ growth
SECONDARY
roots specialized for unusual functions
PROP ROOTS
BUTTRESS ROOTS
PNEUMATOPHORES
AERIAL ROOTS
