Topic 5 - The main tissues (regarding to nutrition value and digestibility)

Question 1

Tissue

Answer 1

Determined as aggregations of morphologically, ontogenetically and functionally similar cells

Question 2

Simple tissue

Answer 2

Tissue composed of a single cell type (ground tissues)

Question 3

Complex tissue

Answer 3

Tissue composed of more than one cell type (vascular tissue)

Question 4

Plant tissue systems

Answer 4

A functional unit of tissues – same functions but in different parts of the body, or in different growth stages

Meristematic
Permanet
o	Dermal tissue
o	Ground tissue
o	Vascular tissue

Question 5

Meristematic cells

Answer 5

Differentiation → primary body (permanent tissues)

Tissues of the primary body → cells become meristematic again dedifferentiation → secondary meristems (e.g.: cutting the stem)

Secondary meristems → redifferentiation → secondary body (vascular tissue, repair wounds)

Question 6

Meristems

Answer 6

Merizein (in greek) = to divide

Dividing, undifferentiated cells with isodiametric (equal in all directions) or fusiform shape

Thin cell wall, large plasma content and high metabolic activity

Initial cells (stem cells) → meristems → permanent tissues (primary body)

Dedifferentiation of permanent tissues can also produce meristems

Question 7

Functions of meristems

Answer 7

Elongation and thickening of stem and roots
Production of lateral roots
Thickening of dermal tissues

Question 8

Dermal tissues

Answer 8

Covers the external part of the plant

Generally one, but often multiple cell layers

Primary and secondary dermal tissues

Question 9

Functions of dermal tissues

Answer 9

o Protection (against herbivores)
o Adsorption of water/minerals
o Water retention
o Gas exchange

Question 10

Primary dermal tissue

Answer 10

Epidermis

Rhizodermis

Question 11

Epidermis

Answer 11

Primary dermal tissue of stem an leaves

Question 12

Epidermal cells + stomata

Answer 12

Tile-like cells with varied shape, no intercellular space and large vacuoles

For monocot species: cells with corks and silicic acid → roughness

The outer cell wall can be covered with cutine, wax or cork → deceasing digestibility

No chloroplastids

Question 13

Stomata

Answer 13

Singular: stoma

Gas exchange, transpiration
Even 100-300 stomata/mm2
Subsidiary cell: water and ion reservoirs

Question 14

Major stomata types

Answer 14

Amaryllis type
o bean shaped guard cells, in cross section they have triangular shape, with subsidiary cells – most common type, mainly in dicots

Grass type
o dumbbell shape guard cells

Question 15

Epidermal appendages

Answer 15

Papillae
Trichromes
Emergences

Question 16

Papillae

Answer 16

Protrusions of epidermal cells
Petal cells are rounded and soft, but for grass and sedge plant they are sharp and coarse (silicic acid, lignin) - irritation

Question 17

Trichromes

Answer 17

Single-celled or multicellular outgrowths  irritation, bezoars, rough texture  animals reluctant to eat
Increase water retention
Bristle hairs
Clinging hairs
Helps dispersal 
Glandular hairs – toxin excretion

Question 18

Emergences

Answer 18

Dermal and ground tissues together

Prickles - protection, mechanical damage

Question 19

Rhizodermis

Answer 19

Root epidermis

• Primary dermal tissue of young roots
• Major difference (in contrast with the epidermis): presence of root hairs and the absence of stomata, cuticle and chlorophylls
• Absorb water and nutrients
• Multiple cell layers are possible

Question 20

Secondary dermal tissues

Answer 20

Secondary growth increase girth (thickness) → epidermis ruptures

A layer of cork cell produced of the cortex below the epidermis

Later cork layers multiplied (phellem) as a result of cell devision and produce the secondary dermal tissue (=periderm)

Accumulation of secondary metabolites in bark (tannic acid, glycosides)

Question 21

Tertiary dermal tissue

Answer 21

Dermal tisses produced of the phloem

= rhytidome

Question 22

Ground tissues

Answer 22

Parenchyma
Secretory tissues
Supporting or mechanical tissues

Question 23

Parenchyma

Answer 23

The most abundant tissue with slightly differentiated cells

More specialized cells evolved from parenchyma: de- and redifferentiation → secondary tissues

Cells are isodiametric, have only primary wall, large vacuoles and prominent intercellular space

Question 24

Function of parenchyma

Answer 24

Basic metbaolism
Storage
Aeration

Question 25

Major types

Answer 25

Chlorenchyma Storage parenchyma Water storage parenchyma Aerenchyma

Question 26

Chlorenchyma

Answer 26

Assimilatory parenchyma Chloroplast containing parenchymal cells photosynthetic function Palisade Spongy

Question 27

Storage parenchyma

Answer 27

Large number of leukoplastids - fatty acids, starch, protein —> high nutritive value (food for animals)

Question 28

Water storage parenchyma

Answer 28

Tissues of succulent plants living in arid habitaits | Cells have thin wall, large vacuoles, and water is absorbed in the form of mucilage

Question 29

Aerenchyma

Answer 29

Parenchyma of water plants and species living in moist habitats Enlarged intercellular cavities Importance for the oxygen supply and gas exchange Low nutrient value

Question 30

Secretory tissues

Answer 30

Intra- and extracellular secretion Endogeneous and exogenous secretion Thin walled cells with numerous nuclei, and many organelles Excretion of secondary metabolites → favours pollinators, or a defence mechanism

Question 31

Intracellular secretion

Answer 31

Metabolites are secreted into vacuoles or cell wall

Question 32

Extracellular secretion

Answer 32

A group of cells secrete metabolites into the intercellular space

Question 33

Endogeneous secretion

Answer 33

Secretory cavities Secretory ducts - For protection and to seal wounds (prevent insect and disease entry) - Resin ducts - Gum ducts - Latex vessels (laticifers)

Question 34

Exogeneous secretion

Answer 34

Secretion to epidermal surface through glands Hydathodes - Secretes water through pores (open water stoma) Salt glands ``` Nectar glands (nectaries) - Sugar-rich liquid with amino acids for pollinators ```

Question 35

Supporting or mechanical tissues

Answer 35

Providing mechanical strength to the growing organs Differentiates usually from parenchyma cells with cell wall thickening

Question 36

Types of supporting or mechanical tissues

Answer 36

Collenchyma | Sclerenchyma

Question 37

Collenchyma

Answer 37

Colla (in latin) = glue Characteristic supporting tissue of your dicot plants Cells are elongated and contain living cytoplasm High tearing resistance → provides flexibility Cells are considerably but unevenly thickened

Question 38

Sclerenchyma

Answer 38

Scleros (in greek) = hard Composed of dead cell with evenly thickened cell wall Lignin is deposited into the walls → low digestibility

Question 39

Main cell types of sclerenchyma

Answer 39

Sclerenchyma fibers Sclereids

Question 40

Sclerenchyma fibers

Answer 40

Extended cells often with tapering ends Small cell lumen and thick wall the longest plant cells Economic value

Question 41

Sclereids

Answer 41

Occur scattered or in clusters Non-elongated, isodiametric cells Sclereids are variable in shape

Question 42

The vascular tissue system

Answer 42

Mosses - single transport cells (no thickening or lignification) Vascular plant = vascular tissue Complex tissue - conducting, parenchymal and sclerenchymal cells

Question 43

Xylem

Answer 43

Wood Conducts water and mineral from the root to the leaves Composed primarily of dead cells

Question 44

components in the xylem

Answer 44

Tracheids Vessels Wood parenchyma Fibers

Question 45

Tracheids

Answer 45

Elongate dead cells with tapering ends Typical in ferns and gymnosperms Specific cell wall thickenings

Question 46

Vessels (xylem)

Answer 46

Consists of vessel elements The wall is considerably thickened and lignified Mainly in angiosperms Vessel elements are short and broad → 10-20 cm size tubers or up to 2 m (oaks), or 5-10 (creepers)

Question 47

Wood parenchyma

Answer 47

The sole living cells of the xylem with a rectangular shape Role: storage and secretion

Question 48

Fibers

Answer 48

Elongate cells with thick, lignified walls

Question 49

Phloem

Answer 49

Bark Conducting sugars, composed primarily of living cells

Question 50

Component of Phloem

Answer 50

``` Sieve cells Sieve tubes Companion cells Fibers Phloem parenchyma ```

Question 51

Sieve cells

Answer 51

similar to Tracheids, narrow, elongated, angular cells Connects to each other with piths Typical in ferns and gymnosperms

Question 52

Sieve tubes

Answer 52

Consists of short and broad sieve-tube elements Mainly in angiosperms Longevity: 1-3 years

Question 53

Sieve plate

Answer 53

Interface between two sieve tube elements

Question 54

Companion cells

Answer 54

(albuminous cells) Carry out all the metabolic functions of the sieve-tube elements Regulate transport and metabolic processes

Question 55

Fibers

Answer 55

Elongate cells with thick, lignified walls (industrial fibers)

Question 56

Phloem parenchyma

Answer 56

Mainly food storage

Question 57

Vascular bundles

Answer 57

``` Simple Compound Concentric Collateral Bundle-sheath ```

Question 58

Simple vascular bundles

Answer 58

Xylem and phloem elements constitute separate bundles

Question 59

Compound vascular bundles

Answer 59

Bundles are composed of both xylem and phloem elements

Question 60

Concentric vascular bundles

Answer 60

Xylem and phloem elements form concentric rings in gross section

Question 61

Collateral vascular bundles

Answer 61

Bundles containing xylem and phloem adjoining each other side by side

Question 62

Bundle-sheath

Answer 62

Parenchymal or sclerenchymal ring around the vascular bundles Temporary storage for nutrients, protection of bundles