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Plant form and function Flashcards

1
Q

Tissue

A

A tissue is a group of 1 or more cell types carrying out specialized functions

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2
Q

What are primary meristems

A

Apical
Intercalary
Axillary bud
Intra fascicular cambium

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3
Q

What are secondary meristems

A

Inter fascicular cambium
Cork cambium

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4
Q

During differentiation process, they undergo changes in

A

cytoplasm, organelles and cell wall

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5
Q

Dermal tissue system

A

Outer covering of the plant e.g; Epidermis
Protective covering in leaves, stems and roots of primary plant body
Tightly packed single cell layer
Usually covered by a cuticle which is a waxy epidermal covering found at aerial parts
Specialized cells such as root hairs,trichomes and guard cells

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6
Q

Functions of ground tissue system

A

Storage
Photosynthesis
Support
Short distance transport

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7
Q

Parenchyma cells

A

Living evem at functional maturity
Cells have primary cell walls which are relatively thin and flexible and most of the cells lack secondary cell walls
Central vacuole present

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8
Q

Parenchyma cells functions

A

Perform most of the metabolic functions of the plant
E.g: photosynthesis fibre
Storage - some cells contains leucoplasts( plastids) in which starch is stored
Most of the parenchyma cells retain the ability to divide and differenciate under suitable conditions. This ability is important in wound repair and tissue culture practises.

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9
Q

Collencyma cells

A

Generally elongated
They have thicker primary cell walls than parenchyma and cell walls are unevenly thickned with cellulose
Young petioles and stems often have strands of collenchyma just beneath the epidermis
Living even at functional maturity

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10
Q

Collencyma functions

A

Giving mechanical support to stems and leaves without restraining growth

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11
Q

Sclerenchyama cells

A

They produce secondary cell walls after cell elongation
Secondary cell walls are thickned by a large amount of lignin
Dead at maturity
2 types of cells known as sclerides and fibers

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12
Q

Sclerenchyma functions

A

Sclerides and fibers are specialized to provide strength and support

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13
Q

Sclereids

A

Sclereids are shorter and wider than fibers and irregular in shape. They have very thick lignified secondary cell walls. They are found in places where growth has stopped e.g.nut shells, seed coats and flesh of coarse fruit

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14
Q

Fibers

A

Fibers are usually grouped in strands. They are long, slender and tapered. Used commercially to obtain fibers. e.g: coconut husk fiber, hemp fibers

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15
Q

Xylem

A

Consist of vessel elements, tracheids, fibers and parenchyma
Vessel elements and tracheids mainly conduct water
They are dead at functional maturity
Fibers give mechanical strength
Parenchyma involves in storage and in radial transport

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16
Q

Vessel elements

A

Found in all angiosperms and some gymnosperms only(Gnetum). Cylindrical and long. Shorter and wider than fibers and have thinner walls than tracheids which are thickened by lignin. They provide support to prevent collapse under tension during water transport.
End walls are perforated with perforation plates while other walls are interrupted by pits. Form xylem vessel by aligning end to end through perforation through which water moves freely.

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17
Q

Phloem

A

Consist of sieve tube elements, parenchyma, companion cells and fibers.
Sieve tube elements are not found in seedless vascular plants and gymnosperms instead long narrow cells called sieve cells are present.

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18
Q

Sieve tube elements

A

Lacks a nucleus, ribosomes, distinct vacuole and cytoskeletal structures
Cytoplasm is restricted to a thin pheripheral layer
Porus plate known as the sieve plate is found at end walls

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19
Q

Companion cells

A

Non conducting cells and are found alongside each sieve tube element. Nucleus and ribosomes serves to adjacent sieve tube elements by forming numerous plasmodesmata
Some companion cells involves in phloem loading and phloem unloading.

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20
Q

indeterminate growth

A

Plants continue growth throughout the life known as indeterminate growth.

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21
Q

Characteristics of meristematic cells

A

Living
roughly isodiametric
are structurally and functionally undifferentiated
central nucleus
dense cytoplasm
ability to multiply

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22
Q

During secondary growth cells in the pericycle converts to

A

Cork cambium

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23
Q

Radial and collateral vascular bundles

A

If xylem and phloem are not found in the same place (not connected) and have different radii it is known as an radial vascular bundle. Dicot and monocot roots contain radial vascular bundles.

If xylem and phloem are connected it is referred as collateral vascular bundles. Monocot and dicot stems contains collateral vascular bundles.

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24
Q

Exarch and endarch xylems

A

Early devoloped xylem is the protoxylem while the later developed xylem is the metaxylem
If the protoxylem is found outer to the metaxylem that is if inward growth of the xylem is present such a xylem is known as an exarch xylem. Found in monocot and dicot roots
And if the protoxylem is found inner to the metaxylem (outward growth) is is known as endarch xylem. Found in monocot and dicot stems.

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25
Closed and open vascular bundles
If the primary meristem of intra fascicular cambium is present between the xylem and the phloem it is known as an open vascular bundle
26
Secondary growth
Increase in diameter of of stems and roots due to the new cells produced by lateral meristems
27
Periderm consist of
Cork cambium and the cork tissue
28
What acts as stomata during gaseous exchange of secondary stems
Lenticells
29
Bark consists of
Bark is all tissues out of the vascular cambium which consists of secondary phloem and periderm ( cork cambium and cork tissue)
30
Heart wood and sap wood
The secondary xylem no longer transporting water or minerals is known as the heart wood Newest layers of the secondary xylem which still transports xylem sap is known as sapwood
31
Hard wood and soft wood
Secondary xylem of dicot angiosperms is known as hard wood while wood of gymnosperms is known as the soft wood.
32
Role of ABA in stomatal closure
ABA is produced in leaves and roots in response to water deficiency and leads to the closure of stomata by removing K ions. This prevents wilting of the plant.
33
In dicot leaves, stomata are found mainly in the
Lower epidermis
34
Only epidermal cells containing chloroplasts
Guard cells
35
Which mesophyll cells contain lower chloroplast
Spongy mesophyll
36
Differences between monocot leaves and dicot leaves in relation to the gaseous exchange
Monocot leaves contains stomata on both lower and upper epidermis while in dicot leaves stomata are mainly found in the lower epidermis There is no distinction in the mesophyll layer of monocot leaves Vascular cylinders (veins) are arranged in net like venation in dicot leaves while parallel venation is seen in monocot leaves
37
Structure of stomata
Stomata are microscopic pores surrounded by guard cells which are specialized epidermal cells containing chloroplast. They are typically bean shaped in angiosperms and contains walls of uneven thickness. Inner walls are thicker and relatively inelastic. Some of the microfibrils radially arrange to form inelastic hoops around the guard cells.
38
In plants gaseous exchange is possible via
stomata and lenticels Gases can be exchanged via the cuticle as well
39
Role of ABA in stomatal closure in drought
• ABA is produced in roots and leaves in response to water deficiency. • Production of ABA leads to close the stomata by removal of K+in guard cells. • This prevents the wilting of the plant.
40
Factors affecting stomatal action
Light stimulates accumulation of K+ in guard cells Decrease in CO2 concentration in substomatal cavity lead to open stomata Internal clock in the guard cells Environmental stresses
41
Collenchyma tissues are absent in
Roots
42
Passive transport methods
Diffusion Osmosis Imbibition Facilitated diffusion Bulk flow
43
Diffusion
In the absence of other forces, the movement of molecules of a substance from a place where it is more concentrated to a place where it is less concentrated due to the random motion of molecules.
44
Osmosis
The diffusion of free water molecules across a selectively permeable membrane
45
Imbibition
The physical absorption of water molecules from hydrophilic substances e.g: Absorption of water molecules from cellulose cell walls
46
Facilitated diffusion
Movement of water and hydrophilic solutes across membranes passively with the help of transport proteins that span the membrane
47
Bulk flow
Movement of water and materials (entire solute) in response to a pressure gradient which is independent of solute concentration.
48
Water potential
The physical property that determines the direction in which water will flow governed by solute concentration and applied pressure Measured in units of megapascals
49
Pressure potential of xylem vessels and living cells
Ψp of a xylem vessel is usually less than -2 MPa as xylem vessels are under tension (negative pressure) Ψp of a living cell is a positive value because living cell is usually under positive pressure due to osmotic uptake of water.
50
Hypotonic solution
When the water potential of the solution is greater than the cell
51
Hypertonic solution
When the water potential of the solution is less than the cell
52
Turgid, flaccid and plasmolyse stages of a cell
Turgid - water potential is greater Flaccid - At equilibrium (isotonic) Plasmolysed - water potential is lower
53
Water and solute movements from soil solution into root hairs
Water enters to root hairs along a concentration gradient and hence it is passive However the solute concentration in root hairs is much more greater than the soil solution hence solute movement occurs against a concentration gradient and hence active
54
Radial transport
Transport of water and minerals entered from soil to root cortex into the xylem of the root is known as radial transport.
55
Routes used in radial transport
Apoplast, symplast and trans-membrane
56
Apoplastic route
The apoplastic route consists of everything external to the plasma membrane of living cells and includes cell walls, extracellular spaces and the interior of dead cells such as vessel elements and tracheids.
57
Symplastic route
The symplast consists of the entire mass of cytosol of all living cells in a plant, as well as plasmodesmata, the cytoplasmic channels that interconnect them
58
Transmembrane route
The transmembrane route requires repeated crossing of plasma membranes as water and solutes exit one cell and enter the next.
59
Cohesion-tension hypothesis
Transpiration provides the pull for ascent of xylem sap and cohesion of water molecules transmits this pull along the entire length of xylem from roots to shoots. Hence xylem sap is normally under tension (negative pressure)
60
Movement of sugars from mesophyll cells to sieve tube elements occurs via
Occurs via symplast through plasmodesmata
61
Constituents of phloem sap
sucrose (as 30% by weight) and it may also contain amino acids, hormones and minerals.
62
Phloem sap moves from source to sink at a rate about
1m/hr
63
Pressure flow hypothesis
1. Loading of sugar into the sieve tube reduces water potential inside the sieve tube elements at the source 2. This causes the sieve tube to take up water from the xylem by osmosis. 3. This uptake of water generates a positive pressure that forces the sap to fl ow along the tube 4. The pressure is reduced by unloading of sugar and consequent loss of water from phloem to the xylem at the sink
64
Transpiration
Removal of water from leaves and other aerial parts of the plant body as water vapour by diffusion is known as transpiration.
65
water loss takes place in plants mainly
Through stomata.-stomatal transpiration upto some extent through cuticle-cuticular transpiration and through lenticels- lenticular transpiration. About 95% of water in plants is lost through stomatal transpiration.
66
Factors affecting the rate of transpiration
1. Light intensity 2. Temperature 3. Humidity 4. Wind speed 5. Concentration of CO2 6. Available water in soil
67
Significance of transpiration to plants
1. Distribute minerals and water throughout the plant. 2. Ascent of water in the xylem. 3. Uptake of water and minerals by roots from the soil solution.
68
Root pressure and guttation
Due to the entering of water into leaves than that lost as transpiration (formation of root pressure) results in the removal of water droplets from leaf tips or leaf margins of some herbaceous plants. Root pressure is never sufficient to push water up distance over meters
69
Guttation takes place through
the hydathode which are formed by special groups of cells located near the ends of small veins and does not take place through the stomata. e.g. Alocasia, Colocasia
70
Nutrition
Is the process of acquiring raw materials and energy from the environment for metabolic activities of organisms
71
Symbiosis
Is the ecological relationship in which 2 species live in close contact to each other.
72
E.g : for mutalism
Legume root nodules with nitrogen fixing bacteria (rhizobium) Mycorrhizae (Association of plants with fungi) Coralloid roots of Cycas with Anabaena
73
E.g : for commensalism
Epipytic Orchids
74
E.g : for parasitism
Semi parasitic Loranthus and Parasitic Cuscuta
75
E.g : for carnivorous plants
Nepenthes, Drosera, Utricularia
76
C,H,O deficiency
Poor growth
77
N
Stunted growth, chlorosis in mature leaves
78
K
Brown or yellow margins in leaves Poorly developed roots Weak stems
79
Ca
Crinkling of young leaves Death of terminal buds
80
Mg
Chlorosis in between veins of mature leaves
81
P
Healthy appearance but very slow development Thin stems Purpling of veins Poor flowering and fruiting
82
S
Chlorosis in young leaves
83
Cl
Wilting Stubby roots Leaf mottling
84
Fe
Cholrosis between veins in young leaves
85
Zn
Crinkled leaves, reduced internode length
86
B
Death of meristems, thick leathery, and discolored leaves
87
Cu
Light green color throughout young leaves drying of leaf tips roots stunted and excessively branched
88
Mo
Death of root and shoot tips, chlorosis in older leaves
89
Ni
Death of leaf tips, chlorosis in older leaves
90
Mn
chlorosis between veins in young leaves
91
Major light receptors involved in photomorphogenesis
Blue light receptors Phytochromes
92
Blue light receptors are involved in
Light induced stomatal opening Phototropism Light induced slowing of hypocotyl elongation
93
Phytochromes are involved in
Seed germination Shade avoidance
94
Photoperiod
Is the interval in 24 hours which a plant is exposed to light
95
Statoliths
Plastids specialized to store starch granules
96
Statolith hypothesis
When a root is horizontally placed statoliths are settled at the bottom if the root cap This sends signals to the root resulting in Ca2+ distribution which finally results in the movement of auxins to the bottom of the root As auxins inhibits cell elongation the lower side grows slowly resulting in positive gravitropism.
97
Types of plant movements are
Tropic Nastic Tactic
98
Thigmonastic movements of Mimosa pudica
Touching results in the sudden loss of turgor pressure of cells in a specialized motor organ called pulvini, causing the leaflets to collapse.
99
Induced structural and chemical defense mechanisms in plants
Morphological changes in the cell wall Forming cork and abscission layers Phenolic compounds Toxic compounds Enzymes that can degrade fungal cell walls or damage insect organs
100
Plant growth regulators definition
Natural or synthetic organic compounds which modify or control physiological processes in plants.
101
Plant Stress
Certain factors in the environment may have potentially adverse effects on plants survival, growth and reproduction.
102
What are mobile elements in plants
Elements which are transported from older leaves to young leaves in a deficiency.
103
Which colours of light involve in stimulation and inhibition of seed germination
Stimulation by red light and inhibition by far red light
104
Thigmomorphogenesis
Changes in the plant form due to mechanical disturbances

Biology (21 decks)

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