TISSUES (CHAPTER THIRTEEN) Flashcards
(111 cards)
1
Q
What’s a tissue ?
A
A group of structurally identical cells, of a common origin and which perform similar functions.
2
Q
Plant tissues may be grouped into two major areas;
A
the meristematic (with undifferentiated cells) and permanent tissues (with differentiated cells)
3
Q
What is Meristematic cells?
A
These are small, undifferentiated cells, having thin walls, large nucleus, dense cytoplasm, small non-centralised vacuoles and constantly undergoing mitosis.
4
Q
CLASSIFICATION OF MERISTEM:
A
- The Apical meristem
- The intercalary meristem
- The Lateral Meristem.
5
Q
Meristematic cells are classified based on:
A
- location in the plant
- ORIGIN(ONTOGENY)
- FUNCTIONS
6
Q
What is an apical meristem?
A
A meristematic cell that is located at the apices of the plant.
7
Q
The apical meristem consists of specialized cells such as:
A
- the dermatogen(outer layer) which gives rise to the epidermis of the stem or the root cap-producing cells of the root.
- Periblem(middle) which forms the cortex of both stem and roots
- the plerome(inner) cells which give rise to cells of the vascular bundle.
8
Q
What’s an intercalary meristems
A
A group of transitory cells which give rise to primary permanent tissues or permanent tissues.
9
Q
Intercalary cells are found in_____ where they cause growth of____.
A
1.nodes of stems (not at the tips)
2 branches.
10
Q
What is a lateral meristem?
A
It is the meristem in the cambium which gives rise to the secondary permanent tissues and ensures the increase in diameter of stems and roots. Found in monocots plant.
11
Q
The branch formed by intercalary meristem is known as;
A
The Nodal Branch, it occurs only in Monocot plants.
12
Q
Unifacial Cambium is responsible for;
A
the formation of Growth rings. It forms the internal cylindrical structure of a
stem and sometimes roots.
13
Q
What is a Periderm?
A
This is a cutinized cambial layer when the epidermis is removed.
It’s a protective layer formed in response to injury to the epidermis.
14
Q
Periderm includes;
A
PHELLOGENS (cork cambium), PHELLEM (cork) & PHELLODERM (secondary cortex).
15
Q
The ______of the periderm contains dead cells which deposit ______. The _______ of the periderm has living cells that lack ______.
A
- outer phellem
- inner phelloderm
- suberin
- suberin
16
Q
What is a Vascular Cambium?
A
This is a cambium which differentiated into the vascular bundles (secondary xylem and phloem).
17
Q
The Vascular Cambium consists of specialized cells such as:
A
- Fusiform initials (elongated cells) extend lengthwise through the stem and differentiate into secondary xylem &phloem(all their cells).
- Ray initials Rays initial (spherical cells) extend sideways and differentiate into Medullary Rays that cut across the xylem and phloem.
18
Q
Classification of meristematic tissues based on ORIGIN(ONTOGENY) :
A
- Promeristem: originate from embryo
- Primary meristem: from the promeristem. Forms the permanent tissues.
- Secondary Meristem: originate from primary meristem. Forms the permanent tissues.
19
Q
Meristematic tissues classified based on FUNCTIONS include:
A
1 PROTODERM: Outer plant tissue (TUNICA). It forms the Epidermis (which protects the outer layer of the plant)
2 PROCAMBIUM: Innermost layer(CORPUS). It forms the Xyelm &phloem. Growth in the primary plant body comes from a group of meristematic cells called procambium.
3 GROUND MERISTEM: forms the Cortex, Pericycle, Medulary rays, and Pith.
20
Q
What is a PERMANENT OR MATURE TISSUE?
A
These are those made up of fully differentiated cells. These are cells which have stopped dividing
21
Q
What is simple and complex permanent tissue?
A
The simple tissue consists of only one type of cell such as the parenchyma, collenchyma, and sclerenchyma while the complex tissue is made up of more than one type of cell but which acts together to perform the same function, e.g. xylem.
22
Q
What is are parenchyma cells.
A
These are living cells, that have thin cell walls and large vacuoles.
23
Q
The main function of parenchyma cells is?
A
the manufacture and storage of food.
24
Q
Where are parenchyma cells found?
A
In the inner leaf tissues (mesophyll), storage cells of the root cortex, pith and cortex of The stem, the pericycle of the stem and roots.
25
What is the collenchyma tissue?
These are tissues made up of elongated irregular cells with primary walls thickened with cellulose, pectin and water.
26
Collenchyma tissue is found;
beneath the epidermis and occurs as the first formed supporting tissue in growing organs of the stems, leaves and flowers.
27
______ persists as the supporting tissue of dicotyledonous herbaceous plants but rarely occurs in roots and monocotyledons.
collenchyma tissues.
28
What are Sclerenchyma cells?
it is a long, narrow cell with cell wall thickened with LIGNIN (i.e lignified).
29
There are two types of Sclerenchymatous cells:
the **elongated** fibres and the **variously shaped** sclereids
30
The dead fibres serve mainly for
mechanical support providing rigidity and elasticity for the plant.
31
In _______ leaves have sclerenchyma cells which form rigid strands providing strength for the epidermal layers in the. In some plants the fibres are so long, they have become of commercial value e.g. hemp (Hibiscus cannabinus).
1. some monocotyledons
pwater lily (Nymphaea lotus)
32
The fibres of sclerechyma provide
Rigidity and Elasticity to the plant. Eg. Water Lilly (Nymphaea lotus), Hemp (Hibiscus cannabinoid).
33
What are the sclereids of sclerechyma?
These are short hard dead cells which occur singly or in groups in the **cortex, phloem of stems** and in the flesh of fruits
34
The complex tissues include what tissues?
the vascular and the secretory tissues.
35
The vascular tissues consist of
the vessels or the xylem conducting water and dissolved salt and the dissolved food conducting vessels or phloem
36
The xylem is made up of
parenchyma cells, fibers, vessels, tracheids and ray cells.
37
Which of the cells of the xylem are dead and empty water-conducting elements?
The tracheids, vessels, fibres, sclereids and the parenchyma cells
38
______ are spindle-shaped cells interconnected by numerous pits of pointed ends, the ______ are tube-like, larger in diameter than tracheids and are laid down end-to-end having lost all or part of their end walls.
1. tracheids
2. vessels
39
The _____ and _____ are basically sclerenchyma cells, which are associated with the xylem or wood.
1. xylem fibres
2. sclereids
40
The fibres are differentiated from vessels and trachied in having _______.
thicker cell walls and smaller cellular cavity
41
The _____ and ______ are primarily mechanical in function.
1. xylem fibres
2. sclereids
42
The xylem parenchyma, also called wood parenchyma may be seen in secondary xylem as
medullary rays.
43
Function of xylem parenchyma?
aid in transporting organic food materials laterally within the stem and also store food for the plant.
44
The constituents of the phloem are
the sieve element, companion cells and parenchyma cells.
45
What are sieve tubes?
These are elongated living cells that have no nuclei but do have vacuoles. The tubes are connected together longitudinally with the end-walls perforated to form sieve plates. Eventhough the sieve tubes
46
What is are Companion cells?
These are living cells and along with the phloem parenchyma assist the sieve tubes in the conduction of food materials sideways to the surrounding tissues.
47
The cytoplasm of the companion cell is in contact with the sieve tube through;
the lining plasmodesmata on the thin dividing walls.
48
What is the phloem parenchyma?
This is a group of living elongated cells usually occurring in vertical rows by the sieve tubes of dicotyledons. The phloem parenchyma cells store up food materials and also aid in their conduction.
49
The function of the sieve tubes:
organic foods are transported in the phloem.
50
What is SECRETARY TISSUES?
These are elongated, much branched ducts or tubular channels. They bear numerous nuclei, with thin cell walls and store food material.
51
Xylem undergoes primary and secondary growth. During the primary growth, the xylem ____ differentiate into ______
1. VESSEL
2. PROTOXYLEM & METAXYLEM.
52
What is a PROTOXYLEM?
They are smaller vessel cells, it is Annular, spiral and Scarlariform in the way their walls are thickened
53
What are METAXYLEM cells?
These are larger vessel cells close to the centre of the stem. It is Reticulate (net-like) and possesses a small pith
54
SECRETORY TISSUE is concerned with the secretion of;
gums, resins, oils, nectar, mucilage, latex, tannins
55
The tissue systems of plants are grouped based on the?
structure and function.
56
The function of the cortex in the stem and roots acts respectively
1. protects the stem
2. in roots it acts as a storage tissue
57
What is The endodermis?
This is the innermost layer of the cortex. It is made up of living cells with large nuclei, and lots of starch grains which gave the layer the name starch sheath.
58
The stalk or petiole of the leaf has a sizeable amount of ______ providing it with strength.
collenchyma cells
59
the Casparian strip.
a band or strip surrounding each cell in the roots
60
The function of the endodermis
It functions as storage tissue for starch grains and prevents loss of water, food and mineral salts from the vascular bundles.
61
_____ separates the endodermis from the vascular bundle, and consists of _____ and _____ cells.
1. Pericycle
2. parenchyma
3. sclerenchyma
62
What is a Pith?
This is the zone that marks the central core of the stem and roots.
63
The pith is made up of?
Large parenchyma cells are mostly found in stems of dicotyledons as a well-developed and distinct portion.
64
The vascular bundle is arranged in a ring in the _____ and _____, but are scattered in the_________.
1. stems of dicotyledons
2. all roots
3. stems of monocotyledons
65
What is a radially arranged vascular bundle?
When the xylem occurs looking like a cross and the phloems are seen singly within the arms of the cross
66
What is a collateral-arranged bundle?
When the xylem and phloem are found in one bundle, in which case the xylem lies on the inside while the phloem is on the outside.
67
What is a bi-collateral vascular bundle arrangement?
When a bundle has the phloem on both poles of the enclosure and the xylem in the middle e.g. the families of Cucurbitaceae, Solanaceae and Convulvulaceae.
68
What is an amphivasal arrangement?
This is **concentric** arrangement in which the phloem is surrounded by the xylem.
69
What is an Amphicribral arrangement?
This is **concentric** arrangement in which the xylem is surrounded by the phloem. e.g. Lycopodium, fern (Lycopodium ceruum).
70
What are tracheids?
These are elongated conducting cells containing pits through which water can flow. They are in close association with the vessels, which are tube-like cells which look like pipes.
71
Vessels are annular if;
the concentric thickened cells of the vessel are separated from one another,
72
Vessels are spiral if;
the rings are joined together like a spring,
73
Vessels are scalariform if;
the internal thickening is net-like and pitted if it has small pits
depressions on the surface of the vessels
74
What are fibre?
These are those sclerenchymatous cells associated with the xylem which provide it with mechanical support.
75
What are function of the parenchyma cells of the xylem?
The parenchyma cells of the xylem aid in food storage since they are the only living cells of all the xylem constituents.
76
What is a vessel?
these are tube-like cells which look like pipes.
77
What is a phloem tissue:
These are cells that occur towards the epidermal cells of the plant and consist of sieves, companion cells and phloem parenchyma. The sieve tubes are tubelike vessels with end walls perforated and the tubes are for longitudinal movement of food from the leaves to storage organs.
78
What is a cambium?
This is the meristematic tissue consisting of actively dividing elongated cells situated between the xylem and the phloem. It is responsible for lateral growth by producing additional xylem and phloem cells in the process of secondary thickening.
79
What is growth?
This is the irreversible increase in the mass of a whole organism or any of its parts due to cellular division and enlargement.
80
The external factors affecting growth are;
water and light
81
the internal factors affecting growth are;
hormones, vitamins and nutrients.
82
What is the function of Vitamins as an internal factor of growth?
These are organic molecules synthesized in the membranes and cytoplasm of cells. They activate enzymes which control the growth and development of plants.
83
The function of nutrients in growth are;
provide the elements and energy for growth.
84
______ is the most important of the internal factors
Hormones
85
_____ is the most important of the internal factors affecting growth
Hormone
86
What is signal transduction?
The biochemical events including the turning on or off of genes
87
_______ stimulates a series of biochemical events including the turning on and off of genes.
The hormone-receptor-complex
88
There are five major groups of plant hormones which includes;
auxins, gibberellins, cytokinins, ethylene and abscisic acid.
89
What are Auxins?
These are a group of substances characterized by their capacity to induce elongation in shoot cells.
90
The main function of auxin is to stimulate _____.
stem elongation and root growth.
91
What is apical dominance?
The assist of plant growth in such a way that side buds are suppressed. Done by auxins
92
Naturally occurring compounds with auxin activity are mainly _____
indole compounds
93
Examples of indole compounds that must be converted to indoleacetic acid (IAA)
indole acetonitrile, indole acetaldehyde and indole pyruvic acid,
94
Examples of indole compounds that may not be converted to lAA and yet act like IAA are
phenylacetic acid (PAA), 4-chloroindoleacetic acid (4-chlorolAA) and indolebutyric acid (IBA).
95
Synthetic auxin-like growth regulators include
naphthalene acetic acid (NAA), 2,4-dichloro phenoxy acetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid
(MCPA).
96
Growth regulators may have inhibitory effects on plants. I.e.____
At low concentrations of 2.4-D, NAA and MCPA kill weeds.
97
What is a Gibberellins (GA)?
Group of plants that stimulate the elongation of internodes and are involved in nearly all of the same regulatory processes in plant development as auxins.
98
______ causes the elongation of cells by producing enzymes that weaken the cell walls.
Gibberellins
99
What are the functions of Gibberellins?
1. stimulate the elongation of internodes and are involved in nearly all of the same regulatory processes in plant development as auxins.
2. They promote seed and bud germination by stimulating the breaking of dormancy. After imbibition of water, the embryo of cereal seeds releases gibberellins, which stimulate the secretion of enzymes that digest the endosperm.
3. They also promote flowering and the development of fruits.
This is by the regulation of the sex of flowers as GA may stimulate more production of either the male or female flowers.
100
The main function of auxin is ?
to stimulate stem elongation and root growth.
101
______ is the growth regulator is principally involved in inducing cell division in plant tissues.
Cytokinins
102
Cytokinins are synthesized in _______
root tips and germinating seeds.
103
Growth enhancement by cytokinins is usually towards enlargement of ____ instead of elongation as auxins do.
1. leaves
104
What are the functions of cytokines?
1. Cytokinins promote cell division by accelerating the events that occur in the G2 (gap) phase of cell division to get into the division proper (prophase).
2. Cytokinins are also involved in cell enlargement, development of chloroplasts, tissue differentiation, cotyledon growth, breakage of dormancy in seeds and the delay of ageing in leaves.
105
_____ promotes the ripening of fruits and, the growth and development of roots, leaves and flowers.
Ethylene
106
Just before ripening, fruits produce _______ and experience an increase in respiration.
1. Ethylene
107
What is climacteric?
The accompanying increase in respiration by fruit just before ripening
108
Function of ethylene
1. Ethylene hastens ripenings by increasing the respiration.
2. stimulates sprouting and germination.
3. causes the stem tip to form a tight crook that may aid the seedling to push to the surface of the soil.
4. Can also induce flowering
109
What is an Abscisic Acid (ABA)?
This is a growth-inhibiting hormone synthesised in plastids from carotenoid pigments.
110
Functions of abscisic acid?
1. inhibits the stimulatory effects of other hormones, It occurs in fleshy fruits where it is thought to prevent seeds from germinating while still on the plant.
2. Induce dormancy
3. the wilting of leaves if abscisic is produced in large amounts which interferes with the retention of potassium ions in the guard cells thereby causing the stomata to close
111
Types of tissue system include
1. EPIDERMAL TISSUE SYSTEM
2. GROUND TISSUE SYSTEM
3. VASCULAR TISSUE SYSTEM
