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Botany - Topic list A > Topic 6 - The histology of plant organs (regarding to nutrition value and digestibility) > Flashcards

Topic 6 - The histology of plant organs (regarding to nutrition value and digestibility) Flashcards

1
Q

Histology of the root

A

Root tip: Initial stem cells → meristematic tissues → permanent tissues

Protection: root cap

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2
Q

The root cap

A

A parenchymal tissue with amyloplasts which sediment to the lower side of the cell

Accumulation of Ca++ → auxin release → gravitropism

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3
Q

Mature region of the root cap

A

Dermal tissue (rhizodermis)
Cortex
Stele

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4
Q

Dermal tissue (root cap)

A

Generally one cell layer

Asymmetrci divisions → root hairs (extensions of dermal cells) → increase absorption surface area

Root hairs live only a few days

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5
Q

Cortex

A

Multiple layers of parenchymal cells (stored nutrients, starch, crystals, latex) or aerenchyma (for water plants)

Transport water and minerals to the vessels

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6
Q

Stele

A

Outer most layer is the pericycle → produce branch roots and secondary dermal tissue

Pith: parenchymal cell layers for storage

Simple xylem and phloem bundels alternate with each other

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7
Q

older root

A

Cellular division in the pericycle → new root cap and root tissues

Generally decreasing digestibility (higher proportion of cell with thickened walls)

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8
Q

Pericycle activity

A

Production of vascular cambium → secondary transport vessels → thickening of the root

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9
Q

Tissues of storage roots

A

Generally lack of mechanical tissues (e.g.: carrot)

Sugar beet → cambia are arranged in concentric circles

More parenchymal cells → better digestibility

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10
Q

Histology of the stem

A

Shoot apex: initial cells (tunica, corpus) → meristems → permanent tissues

No protective cell layer

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11
Q

Epidermis (stem)

A

Generally one cell layer

Similar to the leaf, but less stomata

Cuticle, wax, appendages

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12
Q

Cortex (stem)

A

Monocots - not differentiated into cortex and pith → storage parenchyma

Dicots - below dermal tissue: chlorenchyma, mechanical tissues and less storage parenchyma

For water plants: aerenchyma

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13
Q

Stele (stem)

A

Pith (parenchymal) + vascular bundles with rays

If hollow → pith cavity

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14
Q

Secondary growth (stem)

A

Rare in monocots

Four major types in dicot plants

Secondary growth → higher proportion of lignified cells → decreasing digestibility

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15
Q

Differentiation of the dermal tissues (stem)

A

Epidermis → periderm → rhytidome

Rupture, drop off

Tannins, resin → used as a spice or as medicine

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16
Q

Histology of the wood

A

Soft wood: less fibers, less lignification
Hardwood: more fibers, strong lignification
Heartwood: no water conduction parenchyma cells block the vessels
Sapwood: conduction of water and nutrients

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17
Q

Histology of leaves

A

Determined growth - meristematic activity stops

18
Q

Young leaves

A

Primordia

19
Q

Dermal tissue (leaves)

A

Mainly one cell layer

Cuticle, wax, appendages
Hypostomatic (underneath)
Epistomatic (upper surface)
Amphistomatic (both)

20
Q

Nervation (leaves)

A

Transport, mechanical stability

Closed vascular bundle + bundle sheath

21
Q

Mesophyll (leaves)

A

Middle leaf

Homogenous

Heterogeneous

Assimilation, gas exchange

Secretory cavities, crystals

22
Q

Kranz (leaves)

A

Leaf anatomy

In C4 plants: bundles surrounded by two rings of cell with different plastds

Better CO2 fixation

Species are tolerant to drought

23
Q

Tissues of the flower

A 
Sepals, petals, tepals
Stamens, pollen
Pistil
Fruits
Seeds
24
Q

Sepals, petals, tepals

A

Similar structure to leaves

One layered epidermis with papillae and hairs

Pigments in vacuoles → e.g. carotenoids → nutrient supply

Lack of mechanical tissues

Altogether poor nutritive value

25
Q

Stamens, pollen

A

Stamens are modified leaves

Pollen wall → outer layer consists of sporopollenin

Chemically very stable

Water-solulbe proteins → allergy

26
Q

Sporopollenin

A

Biosynthesised of fatty acids, phenolics and carotenoids

27
Q

Pollenkitt

A

Adhesive material around the pollen

28
Q

Pistil

A

A modified leaf

Stigma

Tissue of the ovary → fruit wall

Chlorenchyma → storage parenchyma

29
Q

Stigma

A

An epidermis with cuticle and glandular hairs → sticky surface to catch and trap pollens

30
Q

Fruits

A

Three regions
Exocarp
Mesocarp
Endocarp

Secretory cavities

31
Q

Exocarp

A

One cell layer covered with cuties, wax, hairs, or it can be lignified

32
Q

Mesocarp

A

In fleshy fruits it’s a multilayered parenchyma storing pigments, and nutrients (fatty acids, CH, proteins)

In dried fruits it consists of sclereids

Can be fused to endocarp

33
Q

Endocarp

A

One or multilayered cells

Can be fused to mesocarp

Hard, stoney endocarp consists of sclereids

34
Q

Taxa (and fruit) specific tissues

A

Fleshy fruits (e.g. berry): storage parenchyma

Dried fruits (e.g. capsule): sclerenchyma

For some types (e.g. drupe) the two types are combined

35
Q

Fibers (fruit)

A

Contraction helps fruits to split open (e.g. pods)

36
Q

Seeds

A

Seed coat + (perisperm (2n)) + endosperm (3c) + embryo

Multilayered storage parenchymal cells

37
Q

Taxon specific cells (seeds)

A

Seed coat can be covered with cuticle, wax, mucilage

38
Q

Parenchyma + sclereids (seeds)

A

One layer, multilayered dry or fleshy

Pigmented cells with tannins

Thick seed coat → digestive problems (shelled seeds)

39
Q

Taxonspecific composition (seed)

A

Carbohydrates, proteins, fatty acids → seed used in animal nutrition (cereals, pulse crops)

40
Q

Absent endosperm and perisperm

A

Nutrients stored in the embryo (cotyledons)

41
Q

Thin hemicellulose walls

A

Good digestibility

Metabolised rapidly → release of nutrients

Botany - Topic list A (17 decks)

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