lecture 9 Plant structure and function Flashcards
1: The cell wall is given strength and rigidity by becoming impregnated with:
a) Cellulose
b) Cutin
c) Suberin
d) Air
e) Lignin
e)Lignin
2: The parenchyma cell is typically:
a) strongly differentiated, isodiametric and alive at maturity
b) relatively undifferentiated, elongated and live at maturity
c) relatively undifferentiated, elongated and dead at maturity
d) strongly differentiated, isodiametric and live at maturity
e) relatively undifferentiated, isodiametric and live at maturity
e)relatively undifferentiated, isodiametric and live at maturity
The casparian strip in the young endodermis is found in:
a) the radial cell walls
b) the tangential cell walls
c) the radial and tangential cell walls
d) all the cell walls
e) between the cells
a) the radial cell walls
The phloem is made up of:
a) sieve tube elements and parenchyma
b) sieve tube elements, companion cells and tracheids
c) seive tube elements and tracheids
d) tracheids, companion cells and parenchyma
e) sieve tube elements, companion cells and parenchyma
e) sieve tube elements, companion cells and parenchyma
The vessel element differs from the tracheid in the:
a) thickening of the lateral wall
b) shape and size
c) organs in which it occurs
d) perforations at the cell ends
e) degree of lignification
d)perforations at the cell ends
The three basic organs of the plant are:
a) root, shoot and leaf
b) root, stem and leaf
c) shoot, leaf and flower
d) shoot, flower and fruit
e) root, stem and shoot
b)root, stem and leaf
The root hairs are outgrowths from:
a) the epidermis at the root tip
b) the endodermis at the root tip
c) the endodermis close behind the root tip
d) the epidermis close behind the root tip
e) the epidermis throughout the root
c)the epidermis close behind the root tip
The main function of the phloem is to transport:
a) Water
b) Oxygen
c) carbon dioxide
d) waste products
e) organic compounds
e)organic compounds
The endodermis forms a barrier between:
a) root and stem
b) cortex and stele
c) root and soil
d) epidermis and stele
e) epidermis and soil
b)cortex and stele
The root xylem is covered in longitudinal ridges known as the:
a) metaxylem points
b) xylem points
c) xylem ridges
d) protoxylem points
e) metaxylem ridges
d)protoxylem points
Describe the Shoot system
- Above ground (usually)
- Elevates the plant above the soil
- Includes the leaves and the reproductive organs
•Many functions including:
–photosynthesis
–reproduction & dispersal
–food and water conduction
Describe the root system
- Underground (usually)
- Anchors the plant in the soil
- Absorbs water and nutrients
- Conducts water and nutrients
- Food Storage
What are the three types of tissues plants have?
1) Dermal;
2) Ground;
3) Vascular
Describe Dermal cells
Dermal cells cover the outside of herbaceous plants
Dermal tissue is composed of epidermal cells, closely packed cells that secrete a waxy cuticle that aids in the prevention of water loss
Describe ground tissue
Ground tissue comprises the bulk of the primary plant body.
–Parenchyma, collenchyma, and sclerenchyma cells are common in the ground tissue
Describe vascular tissue
Vascular tissue transports food, water, hormones and minerals within the plant
–Includes: xylem, phloem, parenchyma & cambium cells.
Epidermis – forms a continuous layer over?
the surface of most primary organs
–Usually 1 cell thick
Ground tissue – typically consists of?
parenchyma
–Endodermis is the inner layer of the root cortex
Describe the features of Vascular tissue – central core in roots (stele)
–Discrete bundles in stems & leaves
–Form a ring in dicotyledonous stems
–Are scattered in monocotyledonous stems
–Divides into xylem & phloem
What are Meristems?
- Plant cell types arise by mitosis from a meristem
- defined as a region of localized mitosis
- Meristems may be at the tip of the shoot or root (apical meristem) or lateral, occurring in cylinders extending nearly the length of the plant
- A cambium is a lateral meristem that produces (usually) secondary growth
- Secondary growth produces both wood and cork (although from separate secondary meristems)
What are parenchyma cells?
Mature plant cells are called parenchymacells
–Other cells & tissues develop from these
–Have thin walls & living contents
–Vary considerably in size
–Development of inter-cellular air-spaces is also variable
–Not differentiated to any great extent
–May become meristematic (by dedifferentiation)
–Often specialised
What are the functions of parenchyma?
- are alive at maturity
- the bulk of ground and vascular tissues
–function in storage, photosynthesis
–also occur within the xylem and phloem of vascular bundles
–the largest occur in the pith region, & are often larger than the vascular bundles
–ray parenchyma cells occur in wood rays, the structures that transport materials laterally within a woody stem
Parenchyma May develop into:
- Collenchyma cells – cellulose thickening in the corners
- Chlorenchyma cells – contain chloroplasts
- Sclerenchyma cells – structural tissue
- Others have – cell inclusions, such as starch grains
Describe the features of Sclerenchyma
Thick walled elements
Secondary wall impregnated with lignin
Lose their living contents at maturity
Are support cells
2 types:
•Fibres
•Sclereids
Parenchyma May develop into?
- Sieve tubes – upper & lower cell walls contain pores lined by strands of cytoplasm penetrating into adjoining cells (called callose)
- Companion cells – thin cells with a nucleus which lie next to sieve tubes
- Dead cells – protoplasm dies – walls become lignified & become woody
- Tracheids – single cells with mainly spiral or ringed thickening (lignin) on their walls
- Vessels – columns of dead cells with no end walls
Describe the features of Seive tube cells
- Characteristic of phloem tissue of angiosperms
- Fairly small, rounded, have a thin unlignified wall
- Difficult to distinguish from parenchyma cells in T.S. section
- Greatly elongated in L.S. sectionjoined end to end to form tubes
Cross walls have perforations – seive platesProtoplasts of adjacent cells are continuous
- Transport organic compounds aroundthe plant
- Alive at maturity
Companion cell – small, rectangular
Dense protoplasmic contents
Describe the features of Phloem
- Important part of vascular system
- Transports carbohydrates produced during photosynthesis
- Provides structural support
- Positioned :
–Outside the xylem in stems & roots
–Below the xylem in leaves
•Compact discrete mass of small, thin walled living cells
Phloem consists of 4 types of what cells?
–Phloem parenchyma
–Sieve tube elements
–Companion cells
–Fibres
Describe the Anatomy of dicotyledonous stems
•Contains a ring of vascular bundles
–Contain xylem (inside)
–Phloem (outside)–Cambium – between X & P,
•one celled & undifferentiated
- Cortex – external to bundles–Pericyclic fibres (sclerenchyma)
- Pith – internal to bundles
- Epidermis – outer layer
Explain secondary thickening
- Starts to form at the end of the 1st year
- Cambium joins with newly formed interfascicular cambium to form a complete ring
–Divides by mitosis, i.e. becomes meristematic
–Produces a ring of 2ndry xylem (on inside)
–Produces a ring of 2ndry phloem (on outside)
- Annual rings – distinct difference between spring xylem & autumn xylem
- Medullary rays – strips of parenchyma running radially through the 2ndry xylem
–Transmits water & foods
•Cork - develops from beneath the epidermis (from phellogen)
–Produces phelloderm on the inside (2ndry cortex)
–Impervious to air, but air enters via lenticels
What are the features of Monocotyledonous stems
- Bundles are scattered (rather than in a ring)
- No cambium in the bundles
- 2ndry thickening does not occur (only in a few spp.)
Describe the structure of the root
- Vascular tissue – is central
- Can become meristematic
- 2ndry thickening can form
- Has an epidermis
- Inner layer is the endodermis
- Cortex – filled with parenchyma
- No chlorophyll
- Storage of starch could be a feature
Describe the leaf structure
- Thin upper epidermis covered with a waxy cuticle
- Below is the mesophyll tissue
–Palisade parenchyma
–Spongy mesophyll
•Water & minerals arrive from the vascular bundles (vein – xylem & phloem, continuous with stem)
–Xylem is on the adaxial (upper) side of the leaf
•Xylem & phloem of leaf bundles – similar to that in the stem
What is the function of the Pea- leaf stoma
- regulates exchange of water vapour, oxygen and carbon dioxide
- Guard cells cover the stoma opening
Compare Dicots vs monocots
Dicot: •2 cotyledons •4x or 5x Floral parts •Net-like veins •3 pores in pollen •Bundled vascularture
Monocot •I cotyledon •3x Floral parts •Parallel veins•1 pore in pollen •Dispersed vasculatur
