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BIOLOGY STRUCTURED > Plant form and function 2 > Flashcards

Plant form and function 2 Flashcards

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1
Q

Reproductive organs (gametangia and sporangia) are protected by what?

What is the function of it?

A

are protected by sterile cell
layers to prevent desiccation of mother cells. (gamete forming cells and spore forming cells).

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2
Q

Gametophytes produce gametes by….

A

mitosis

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3
Q

What is a feature of all land plants?

A

carryout internal fertilization to prevent desiccation of gametes.

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4
Q

What is there in the archegonium?

A

Female egg (ovum) is retained in the archegonium

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5
Q

Male gametes released from…

A

(antherozoids) are released from the antheridium.

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6
Q

Does seedless plants depend on external water for fertilization?

A

Yes

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7
Q

Do seed plants depend on external water for fertilization?

A

No

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8
Q

What happens after delay of meiosis of sexually reproducing terrestrial plants?

A

*After fertilization, diploid zygote is retained within the gametophyte to produce an embryo which is nourished by the gametophyte.

  • Embryo develops into the diploid sporophyte.
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9
Q

Describe about the occurrence of the sporophyte generation

A
  • Delay of meiosis after fertilization results in creating a diploid sporophytic
    generation.
  • Diploid sporophyte produces haploid spores by meiosis.
  • Spores grow into haploid gametophytes.
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10
Q

What happens in the course of evolution of the land plants?

A

In the course of evolution of land plants, diploid sporophytic generation acquire adaptations needed for successful colonization on land and become dominant plant in the life cycle.

Gametophytic generation gradually reduced and has
become dependent on the sporophytic generation in seed plants.

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11
Q

Describe the Pogonatum gametophyte?

A
  • Gametophyte is the dominant plant, larger and longer-living than sporophyte.
  • Gametophyte is photosynthetic.
  • ‘Stem’, ‘leaves’, and rhizoids are present in the gametophyte
  • Gametophytes are dioecious (unisexual). Mature male gametophytes produce
    antheridia in which several sperms are produced.
  • Female gametophytes produce archegonia. A single egg is produced within the
    archegonium
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12
Q

Sporophyte of Pogonatum?

A
  • The embryo is also retained within the archegonium and develops into the diploid
    sporophyte by obtaining nutrients from the gametophyte.
  • The sporophyte remains attached to the gametophyte.
  • The sporophyte consists of a foot, seta and a capsule (sporangium).
  • The foot absorbs nutrients and water from the gametophyte.
  • The capsule produces spores by meiosis. Homosporous.
  • If spores are dispersed to a favourable habitat, (such as moist soil or tree bark)
    they may germinate and grow into a green, branched fi lament called protonema.
  • Protonema produces buds that grow into gametophytes.
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13
Q

Fertilization process of pogonatum?

A
  • The egg is not released.
  • Flagellated, motile sperm swims through external water towards egg, entering
    the archegonium in response to chemical attractants.
  • Sperm fuses with the ovum resulting diploid zygote. This occurs in the
    archegonium.
  • After fertilization zygote develops into the embryo.
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14
Q

terrestrial features of the Nephrolepis (sporophyte structure)

A

Sporophytes have more complex structure.
* Plant body is differentiated into roots, stem and leaves.
* Cuticle is found on aerial parts of the plant body
* Stomata are developed on aerial parts for gaseous exchange.
* Two types of vascular tissues, xylem and phloem are developed
* They have fi ddlehead young leaves
* Stem is an underground rhizome
* Leaves are compound pinnate leaves
* Long underground branches called stolons arise from the rhizome \
which gives rise to new plantlets.

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15
Q

Gametophyte of nephrolepis?

A
  • Sporophyte is dominant
  • Gametophyte is reduced and short lived.
  • Both sporophytes and gametophytes are independent and photosynthetic.
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16
Q

sporangia of nephrolepis?

A
  • Sporangia are developed as clusters called sori on the underside of mature
    leafl ets. Sori are covered by the indusium, protecting the young sporangia
    from desiccation. Spores are produced in the sporangium by meiosis and are
    homosporous.
  • When the sorus matures, indusium dries up and shrivels, exposing mature sporangia.
  • Under dry environmental conditions sporangium wall ruptures, releasing spores.
  • Spores are dispersed by wind.
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17
Q

Gametophyte of nephrolepis?

A
  • Gametophyte is a small heart shaped, macroscopic, green coloured photosynthetic
    thallus.
  • Rhizoids develop on the ventral surface.
  • Gametophytes are monoecious (bisexual). Antheridia and archegonia are
    developed on the ventral side.
  • Antheridium produces fl agellated sperms and releases them into the external
    environment.
  • Archegonium produces one egg and retains it.
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18
Q

Gametophyte of nephrolepis?

A

Small heart shaped, macroscopic, green coloured photosynthetic
thallus.

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19
Q

Describe about fertilization of nephrolepis?

A
  • Motile sperms swim through external water towards egg entering the archegonium
    in response to chemical attractants.
  • Sperm fuses with the egg resulting the diploid zygote.
  • After fertilization zygote develops into the embryo and then to the young
    sporophyte while retained in the gametophyte.
  • All the developmental stages are nourished by the gametophyte.

When the young sporophyte develops its photosynthetic tissues, it becomes an
independent plant.

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20
Q

Describe about the sporophyte of sellaginella?

A
  • Sporophytes are dominant and photosynthetic.
    Sporophyte plant body is differentiated into roots, stem and leaves. Vascular tissues present. Herbaceous.
  • Heterophyllous leaves are arranged as pairs.
  • Stem is dorsiventrally fl attened.
  • Sporangia are borne on the specialized leaves called sporophylls.
  • Sporophylls are compactly arranged in a terminal strobilus.
  • Two types of sporophylls called megasporophyll and microsporophyll are
    arranged in the same strobilus.
  • Megasporophyll produces a single megasporangium and microsporophyll
    produces a single microsporangium.
  • Morphologically two different types of spores are produced. This nature is called
    heterospory.
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21
Q

Megasporangium of sellaginella?

A

Megasporangium produces four large megaspores by meiosis.
Female gametophyte is multicellular, surrounded by the thick wall of megaspore,
Few rhizoids develop.
* Photosynthetic, but partially depend on stored food in the megaspore.
* Archegonia develop at the superficial regions and are fully embedded in the gametophytic tissue.

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22
Q

Microsporangium of selaginella?

A
  • Microsporangium produces numerous small microspores by meiosis.
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22
Q

Microsporangium of selaginella?

A
  • Microsporangium produces numerous small microspores by meiosis.
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23
Q

Similarity of megaspore and the microspore?

A

Both types of spores have thick/tough walls

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24
Q

Male gametophyte features?

A

Both types of spores have thick/tough walls.

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25
Q

Male gametophytes of selaginella?

A

Microspores are retained in the microsporangium and develop into young male
gametophytes.
* Young male gametophytes are enclosed by the wall of microspore which, are
released by the microsporangium.
* In the external environment they become mature male gametophytes.
* Male gametophytes is microscopic, enclosed in the microspore wall, non-
photosynthetic, depend on stored food.
* Male gametophytes produce fl agellated sperms and release them into the external
environment.

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26
Q

Female gametophytes of selaginella?

A

Megaspores are released into the external environment. In the external
environment they develop into female gametophytes.
* Female gametophyte is multicellular, surrounded by the thick wall of megaspore,
Few rhizoids develop.
* Photosynthetic, but partially depend on stored food in the megaspore.
* Archegonia develop at the superfi cial regions and are fully embedded in the
gametophytic tissue.

  • One egg is produced inside the archegonium.
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27
Q

Fertilization of selaginella?

A
  • Sperm swims towards the egg (n) using flagella through external water, entering into the archegonium and fertilizes the egg (n) resulting in a zygote(2n).
  • Zygote develops to form an embryo and then embryo develops to form a young sporophyte by obtaining nutrients from the female gametophyte.
  • Sporophyte generation is the larger and more complex form in the alternation of generation
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28
Q

Sporophyte of cycas?

A

Sporophytes are the dominant photosynthetic plants in the life cycle, gametophytes
are reduced and depend on the sporophyte throughout its life.

Sporophytes which produce megaspores are called female plants and those which produce microspores are called male plants.

  • Mature female plant produces a crown of megasporophylls.
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29
Q

Sporophyte of cycas?

A

Sporophytes are the dominant photosynthetic plants in the life cycle, gametophytes
are reduced and depend on the sporophyte throughout its life.

Sporophytes which produce megaspores are called female plants and those which produce microspores are called male plants.

  • Mature female plant produces a crown of megasporophylls.
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30
Q

Features of cycas plant?

A

Sporophytes are a perennial tree with roots, stem and leaves.
* Stem is unbranched columnar and woody.
* Leaves are arranged in crowns.
* Compound leaves show xerophytic adaptations and young leaves are fi ddleheads.
* Sporophytes are heterosporous and dioecious. Sporophytes have developed a tap
root system.
* Secondary growth is present.

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31
Q

What is the nature of the cycas sporophyte?

A

Female plants:

  • Sporophytes which produce megaspores are called female plants and those
    which produce microspores are called male plants.
  • Mature female plant produces a crown of megasporophylls.

Male plants:
Mature male plants produce male cones with microsporophylls which consist of microsporangia on the lower surface. Large numbers of microspores (n) are produced from microspore mother cells (2n) within the microsporangium by meiosis.

32
Q

Describe about the cycas the megasporangium?

A
  • Megasporangium is enclosed in the protective layer called integument to form the ovule. Integument has a small pore in the distal end of the ovule called micropyle.
  • One of the cells in the megasporangial tissue differentiates into a single megaspore mother cell. Megaspore mother cell undergoes meiosis to form four haploid megaspores out of which only one remains functional.
  • The remaining megasporangial tissue functions as nucellus which provides nourishment.
  • Megaspores are not released to the external environment megaspore develop into the female gametophyte (n) while within the ovule. Mature ovule contains the female gametophyte. The female gametophyte produces several archegonia.
    Each archegonium produces a single egg cell within it.
33
Q

Describe about the cycas the megasporangium?

A
  • Megasporangium is enclosed in the protective layer called integument to form the ovule. Integument has a small pore in the distal end of the ovule called micropyle.
  • One of the cells in the megasporangial tissue differentiates into a single megaspore mother cell. Megaspore mother cell undergoes meiosis to form four haploid megaspores out of which only one remains functional.
  • The remaining megasporangial tissue functions as nucellus which provides nourishment.
  • Megaspores are not released to the external environment megaspore develop into the female gametophyte (n) while within the ovule. Mature ovule contains the female gametophyte. The female gametophyte produces several archegonia.
    Each archegonium produces a single egg cell within it.
34
Q

Describe about the pollen grain of cycas?

A
  • They develop into pollen grains within the sporangium and then discharge.
  • Pollen grains are dispersed by wind and deposited on the micropyle of a mature ovule is called pollination.
  • Pollen grains enter into pollen chamber of the ovule through the micropyle.
    *In the pollen chamber, pollen grains develop into male gametophytes. Male gametophyte consists of a branched pollen tube which involves in absorption of nutrients from the nucellus. Male gametophyte is short-lived.
  • Produce two large sperms with a spiral band of numerous cilia.
  • The basal end of the pollen tube ruptures releasing sperms into the archegonial chamber of the ovule. Sperms swim through the liquid medium and fertilize the egg resulting the 2n zygote.
34
Q

Describe about the pollen grain of cycas?

A
  • They develop into pollen grains within the sporangium and then discharge.
  • Pollen grains are dispersed by wind and deposited on the micropyle of a mature ovule is called pollination.
  • Pollen grains enter into pollen chamber of the ovule through the micropyle.
    *In the pollen chamber, pollen grains develop into male gametophytes. Male gametophyte consists of a branched pollen tube which involves in absorption of nutrients from the nucellus. Male gametophyte is short-lived.
  • Produce two large sperms with a spiral band of numerous cilia.
  • The basal end of the pollen tube ruptures releasing sperms into the archegonial chamber of the ovule. Sperms swim through the liquid medium and fertilize the egg resulting the 2n zygote.
35
Q

What does the cycas zygote develop into?

A

the embryo

36
Q

What does the cycas integument become?

A

seed coat

37
Q

What does the remaining cycas female gametophyte become?

A

Remaining female gametophyte becomes the endosperm which provides nutrients for the developing embryo during seed germination.

38
Q

What does the cycas ovule become?

A

seed

39
Q

Describe the sporophyte of flowering plants?

A

Sporophyte produces the reproductive structures called flowers.

A flower is a specialized shoot with four whorls of modified leaves named sepals, petals, stamens and carpels.

40
Q

Describe about the sepals of the flowering plants

A

Sepals are usually green, enclose and protect the fl ower before it opens.

41
Q

Describe about the petals of the flowering plants?

A

Petals are brightly coloured in most flowers and aid in attracting pollinators. (But
wind pollinated flowers generally lack brightly coloured parts).

42
Q

Describe about the petals of the flowering plants?

A

Petals are brightly coloured in most flowers and aid in attracting pollinators. (But
wind pollinated flowers generally lack brightly coloured parts).

43
Q

Do petals and sepals involve in the process of reproduction?

A

The sepals and petals are sterile fl oral organs. They do not directly involve in
reproduction.

44
Q

What are microsporophylls in flowering plants?

A

stamens

The stamen consists of a stalk called fi lament and two terminal lobes called
anther.

45
Q

What does anther of flowering plants have?

A

microsporangia (pollen sacs) containing microspore mother
cells which produce microspores by meiosis. Microspores develop into pollen
grains within the anther.

46
Q

What does the pollen grain contain?

A

two nuclei, the tube nucleus and generative nucleus

47
Q

What are carpels of the flowering plants?

A

Carpels are the megasporophylls. At the tip of the carpel is a sticky stigma that
receives pollens. The swollen base of the carpel forms the ovary. Ovary contains
one or more ovules A long, slender neck called style connects ovary with stigma.

  • Ovule produces four megaspores by meiosis of which only one becomes
    functional.
48
Q

What does the functional megaspore of the flowering plants develop into?

A

Functional megaspore develops into the female gametophyte called the embryo
sac. It is a highly reduced microscopic structure.

49
Q

What does the mature embryo sac of the flowering plants contain?

A
  • The mature embryo sac consists of eight nuclei contained within seven cells-
    three antipodal cells, two polar nuclei in the central cell, two synergids and one
    egg.
50
Q

How are plants adapted to the cross pollination?

A
  • Typical characteristics of flowers like such as colour and odour favour cross pollination.
  • In addition, some plants show special types of adaptations cross pollination.
    e.g. heterostyly, self infertility, unisexuality
51
Q

what is the significance of cross pollination?

A

Cross fertilization allows shuffling of genes within a species, producing new genetic combinations resulting increased genetic variation within the species.

These features are very important for survival and
also might lead to evolution.

52
Q

What is the significance of cross pollination?

A

Cross pollination results in cross fertilization. Cross fertilization allows shuffling of genes within a species, producing new genetic combinations resulting increased genetic variation within the species.

These features are very important for survival and
also might lead to evolution.

53
Q

How does fertilization occur of flowering plants?

A
  • The pollen grain germinates after it is placed on the stigma.
  • It extends a pollen tube that grows down through the style of the carpel.
  • The generative nucleus divides forming two sperm nuclei.
  • When the pollen tube reaches the ovary, it moves through the micropyle (The pore
    in the integuments of the ovule) and discharges two sperm nuclei into the embryo
    sac.
54
Q

How does double fertilization occur in angiosperms?

A

One sperm nucleus fuses with the egg cell forming a diploid zygote and the other sperm nucleus fuses with the 2 polar nuclei.

This type of fertilization is called
double fertilization and is unique to angiosperms.

55
Q

What happens after double fertilization?

A

After double fertilization, the ovule matures into a seed. The zygote develops into the embryo.

The triploid nucleus develops into the endosperm that store food.

56
Q

What is the significance of double fertilization?

A
  • The significance of double fertilization is that it synchronizes with the development of the embryo.
  • If fertilization does not occur that prevents plants from wasting nutrients on infertile
    ovules.
57
Q

What does the seed contain?

A

The seed consists of the embryo, endosperm with store food and a seed coat.
* Seeds are enclosed in the fruit.

58
Q

Describe the nature of fruits of flowering plants?

A
  • Fruit is an enlarged and developed ovary, usually after being stimulated by fertilization.
  • Fertilization triggers hormonal changes that cause the ovary to form a
    fruit.
  • If a flower has not been pollinated, fruit does not develop, and entire flower falls away.
59
Q

During the fruit development, what happens to the ovary wall?

A

During fruit development, the ovary wall gets converted to the pericarp.

60
Q

Examples of parthenocarpy fruits?

A

Banana

61
Q

What can be induced with plant growth substances to get seedless fruits?

A

Grapes, Orange

62
Q

Name examples for parthenogenesis?

A

certain grasses

63
Q

What does parthenogenesis result in?

A

In parthenogenesis,
* the egg is resulted by mitosis and hence is diploid,or
* haploid ovum fuses with a polar nucleus, or
* the genetic content of the egg is duplicated to become diploid, enabling seed
development without fertilizing by the sperm.

64
Q

What are the main causes of seed dormancy?

A

Presence of inhibitors, presence of thick/strong seed coats, presence of seed
coats impervious to water

65
Q

What does blue light photoreceptors induce?

A

phototropism
the light induced opening of stomata and the
light induced slowing
of hypocotyl elongation that occurs when a seedling breaks ground.

66
Q

What does phytochrome photoreceptors induce?

A

seed germination and shade avoidance.

67
Q

What are Preexisting structural and chemical defense mechanisms?

A
  • Amount and quality of wax and cuticle that cover the epidermal cells
  • The structure of the epidermal cell walls and thickness
  • The size, location and shapes of stomata
  • Toxic compounds, alkaloids (eg. Nicotine), phenolics (eg. Flavonoids,
    lignin & tannins), terpenoids (eg. Azadirachtin) and lectin
  • Thorns, pricks, trichromes
68
Q

Explain about statolith hypothesis

A

The aggregation of statoliths at the low points of root cap cells triggers re-distribution
of Ca2+ which causse lateral transport of auxin within the root. As a result, Ca and
auxin get accumulated at lower side of elongation zone of root. At high concentration
of auxin, cell elongation is inhibited resulting slow growth on lower side and more
rapid elongation on upper side. Consequently, the root grows downwards.

69
Q

How do plants act as touch specialists?

A

During evolution, some plant species have become ‘touch specialists’. Climbing plants have tendrils that coil rapidly around support.

Tendril usually grows straight until it touches a support. The contact stimulates differential growth on opposite sides of the
tendril.

The directional growth of tendril towards support is called thigmotropism.

Other touch specialists, respond to touch by rapid leaf movements. E.g. Mimosa pudica collapses its leaflets when touched.

Touching results in a sudden loss of turgor of cells in a specialized motor organ called pulvini, causing the leaflets to collapse.
This response is called thigmonasty.

70
Q

What are the two types of stresses?

A
  1. Abiotic stress
  2. Biotic stress
71
Q

What are examples for abiotic stresses?

A
  1. Drought stress
  2. Cold stress
  3. Salt stress
72
Q

Explain about the drought stress

A

Plants may wilt when water loss by transpiration exceeds water
absorption.

Prolonged drought may even kill a plant. Plants have control systems that
enable them to cope with the drought/ water deficit conditions.
Water deficit stimulates increased synthesis and release of abscisic acid (ABA), which
acts on guard cell membrane, closing stomata to reduce transpiration.

73
Q

Example for drought stress?

A

In grasses, the leaves roll in to a tube-like shape which reduces the surface area to reduce transpiration.

Some plants shed their leaves during seasonal drought.

74
Q

Describe about cold stress

A

When cell membrane cools below a critical temperature it looses its
fluidity due to the lipids become locked in to crystalline structure. This blocks the
transport across the membrane and affects the function of the cell.
Plants respond to cold stress by altering the lipid composition of their membranes.
They increase the proportion of unsaturated fatty acids which keeps the membranes
more fl uid at low temperature.

75
Q

Describe about the freezing which is another cold stress

A

Freezing is another cold stress. Water in the cell wall and intercellular spaces freezes
before freezing the solute-rich water in the cytosol. The reduction of liquid water in the
cell wall lowers the extracellular water potential causing water in the cytosol to leave.

This results high concentration of solutes in the cytoplasm which is harmful and may
lead to cell death.
Before the onset of winter, the cell of frost-tolerant plants increases cytoplasmic levels
of specifi c solutes such as sugars that help to reduce the loss of water from the cell
preventing dehydration.

76
Q

Describe about salt stress

A

An excess of salts (high salinity) in soil lowers the water potential of soil
resulting reduced water potential gradient from soil to root. This leads to reduction of
water uptake by roots.
In general too high salinity in soil is toxic toplants.
Many plants can respond to moderate soil salinity by producing solutes that are well
tolerated at high concentrations. These are organic compounds that keep the water
potential of cell more negative than that of the soil solution.
A few plants that are salt-tolerant (halophytes) have developed salt glands, which
secrete excess salts out of the plant across leaf surfaces. e.g. many mangrove plants

77
Q

What are Induced structural and chemical defense mechanisms?

A
  • Morphological changes in the cell wall
  • Formation of cork and abscission layers
  • Phenolic compounds
  • Toxic compounds
  • Enzymes that can degrade fungal cell walls or damage insect organs

BIOLOGY STRUCTURED (13 decks)

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