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Plant Reproduction Flashcards

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1
Q

State some unique feature of Pogonatum?

A

Gametophyte is differentiated into false roots,stems and leaves
Capsule is divided into capsule, seta and foot
Spores germinate into protonema

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2
Q

State a unique feature of the plant Nephrolepis?

A

Both sporophyte and the gametophyte are independent but sporophyte is dominant

Gametophyte is monoecious

Homosporus sporophyte which produces clusters of sporangia known as sori

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3
Q

Structure of the gametophyte of nephrolepis

A 
Small
Macroscopic 
heart shaped 
green colored 
Photosynthetic 
Thallus
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4
Q

Nephrolepis essay points

1) Status of sporophyte
2) Status of gametophyte
3) Structure of gametophyte
4) Structure of sporophyte
5) Sporangia and spores
6) Gametangia and gametes
7) Fertilization and development of sporophyte

A

1) and 2)

Sporophyte is dominant
Gametophyte is reduced and short lived.
Both sporophytes and gametophytes are independent and photosynthetic.

3)

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 fiddlehead 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.

4)

• Sporangia are developed as clusters called sori on the underside of mature leaflets.
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.
When spores are dispersed to a favourable habitat they may germinate and grow into a gametophyte

5)

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.

6)

  • Antheridium produces flagellated sperms and releases them into the external environment.
  • Archegonium produces one egg and retains it.
  • Motile sperms swim through external water towards egg entering the archegonium in response to chemical attractants.

7)

  • 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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5
Q

Plants with monoecious gametophyte

A

Nephrolepis

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6
Q

Plants with dioecious gametophyte

A

Pogonatum
Selaginella
Cycas
Angiosperms

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7
Q

Plants depend on external fertilization for fertilization

A

Pogonatum
Nephrolepis
Selaginella

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8
Q

Plants do not depend on external water for fertilization

A

Cycas

Angiosperms

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9
Q

Plant which produce only one egg

A

Angiosperms only

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10
Q

Motile sperms absent in these plants.

A

Angiosperms

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11
Q

Only plants with false stems roots and leaves

A

Pogonatum

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12
Q

Number of flagella in the sperm

1) Pogonatum
2) Nephrolepis
3) selaginella
4) cycas
5) angiosperms

A

1) biflagellated
2) multiflagellated
3) biflagellated
4) flagellated
5) absent

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13
Q

Homosporus plants

A

Pogonatum

Nephrolepis

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14
Q

Heterosporous plants

A

Selaginella
Cycas
Angiosperms

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15
Q

Monoecious sporophyte

A

Pogonatum
Nephrolepis
Selaginella

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16
Q

Dioecious sporophyte

A

Cycas

Angiosperms

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17
Q

Photosynthetic sporophyte

A 
Pogonatum when young 
Nephrolepis 
Cycas 
Selaginella 
Anthophytes
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18
Q

Photosynthetic gametophyte

A

Pogonatum
Nephrolepis
Partially photosynthetic female gametophyte of selaginella

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19
Q

Selaginella essay points

1) Status of sporophyte
2) Status of gametophyte
3) Structure of sporophyte
4) Sporangia and spores
5) gametophyte
6) Gametangia and gametes
7) Fertilization and development of sporophyte

A

1) and 2)

  • Sporophytes are dominant and photosynthetic.
  • Gametophytes are reduced in structure and short-lived, partially depend on the sporophyte.

3)

• Sporophyte plant body is differentiated into roots, stem and leaves. Vascular tissues present.
Herbaceous.
• Heterophyllous leaves are arranged as pairs.
• Stem is dorsiventrally flattened.

4)

  • 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 megasporngium and microsporophyll produces a single microsporangium.
  • Morphologically two different types of spores are produced. This nature is called heterospory.
  • Megasporangium produces four large megaspores by meiosis.
  • Microsporangium produces numerous small microspores by meiosis.
  • Both types of spores have thick/tough walls.

5)

  • 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.
  • 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 superficial regions and are fully embedded in the gametophytic tissue.

6)

  • Male gametophytes produce flagellated sperms and release them into the external environment.
  • Archegonia develop at the superficial regions and are fully embedded in the gametophytic tissue.
  • One egg is produced inside the archegonium.

7)

  • 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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20
Q

Unique features of selaginella

A

Presence of heterophyllous leaves

Vegetative leaves become the sporophylls and they organized to form a strobilus

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21
Q

State some plants which possess rhizoids

A

Pogonatum gametophyte
Nephrolepis male gametophyte
Selaginella female gametophyte

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22
Q

State the substrate of the following plant phylum

1) bryophyta
2) pterophyta
3) lycophyta
4) cycas

A

1) wet env, moist terrestrial habitat, tree bark
2) moist env
3) terrestrial and some are epiphytes
4)

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23
Q

State the dominant plant in the following

1) Pogonatum
2) Nephrolepis
3) selaginella
4) cycas
5) mango

A

1) dominant gametophyte ( independent, long lived )
2) dominant sporophyte
3) dominant sporophyte
4) dominant sporophyte
5) dominant sporophyte

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24
Q

State 2 types of stems produced by lycophyta

A

Upright stems

Ground hugging stems

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25
Q

State 2 groups in phylum lycophyta

With examples for each

A

Club mosses
Lycopodium

Spike mosses
Selaginella

26
Q

State 2 ways by which the gametophyte of lycophyta is nourished

A

Some gametophyte live above the ground and they are photosynthetic

Some live below the ground and they are nourished by symbiotic fungi

27
Q

Dependency of sporophyte and gametophyte in plants

1) Pogonatum
2) Nephrolepis
3) selaginella
4) cycas and anthophytes

A

1) gametophyte is independent and photosynthetic
Sporophyte is dependent but photosynthetic when young

2) sporophytes independent and photosynthetic
Gametophyte is independent and photosynthetic but not dominant

3) sporophyte is independent and photosynthetic
Gametophyte is dependent but female gametophyte is partially Photosynthetic

4) sporophytes are independent and photosynthetic
Gametophytes are dependent and not photosynthetic

28
Q

Cycas essay points

1) external features and dominant in the life cycle sporophytes
2) spores
3) ovule
4) gametophyte ( both male and female) and gametes
5) pollination and fertilization
6) formation of the fruit and dispersal

A

1) • Sporophytes are the dominant photosynthetic plants in the life cycle, gametophytes
are reduced and depend on the sporophyte throughout its life.
• 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 fiddleheads.
• Sporophytes are heterosporous and dioecious. Sporophytes have developed a tap root system.
• Secondary growth is present.

2) • 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.

3) • 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.

4) • 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.
• 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.
• They develop into pollen grains within the sporangium and then discharge.
• 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.

5) • Pollen grains are dispersed by wind and deposited on the
micropyle of a mature ovule is called pollination.
• 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.

6) • Zygote develops into the embryo
• Remaining female gametophyte becomes the endosperm which provides nutrients for the developing embryo during seed germination. Integument becomes the seed coat.
• The ovule becomes the seed.
• Seed is the dispersal unit which contains the embryo and stored food that are enclosed in the seed coat.
• Seeds are dispersed and under favorable environmental conditions seeds germinate producing the seedlings (young Sporophyte).

29
Q

What is the dispersal unit of seed plants

A

Seed

30
Q

Unique features of cycas

A

Note book

31
Q

Distinct features of phylum anthophyta

A

Do it

32
Q

Describe the 4 whorls in a flower

A
  • A flower is a specialized shoot with four whorls of modified leaves named sepals, petals, stamens and carpels.
  • Sepals are usually green, enclose and protect the flower before it opens.
  • Petals are brightly coloured in most flowers and aid in attracting pollinators. (But wind pollinated flowers generally lack brightly coloured parts).
  • The sepals and petals are sterile floral organs. They do not directly involve in reproduction.
  • Stamens are the microsporophylls.
  • The stamen consists of a stalk called filament and two terminal lobes called anther.
  • 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.
33
Q

Stamens in flower

A
  • Stamens are the microsporophylls.
  • The stamen consists of a stalk called filament and two terminal lobes called anther.
  • Anther is made up of microsporangia (pollen sacs) containing microspore mother cells which produce microspores by meiosis. Microspores develop into pollen grains within the anther.
  • A pollen grain contains two nuclei, the tube nucleus and generative nucleus.
34
Q

Carpels in flower

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.
• Functional megaspore develops into the female gametophyte called the embryo sac. It is a highly reduced microscopic structure.
• The mature embryo sac consists of eight nuclei contained within seven cells-
three antipodal cells,
two polar nuclei in the central cell,
two synergids
one egg

35
Q

Define pollination

A

• Transfer of pollen grains to a mature stigma is known as pollination.

36
Q

Define self pollination

A

• In some plant species, pollen grains are transferred from an anther of a flower on to the stigma of the same flower. This is self-pollination

37
Q

Define cross pollination

A

• Pollen may be transferred to a stigma of a different flower. This is cross pollination.

38
Q

Most beneficial type of pollination to the plants

A

Cross pollination

39
Q

Characteristics in flowers which favor cross pollination

A

• Typical characteristics of flowers like such as colour and odour. favour cross pollination by attracting pollinators
• In addition, some plants show special types of adaptations to enhance cross pollination.
e.g. heterostyly, self infertility, unisexuality

40
Q

State 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.

41
Q

Define double fertilization

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.

43
Q

Describe the process of fertilization in angiosperms

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.
  • 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.
44
Q

State post fertilization changes in the ovary

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.
  • 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.
  • During fruit development, the ovary wall gets converted to the pericarp.
45
Q

State 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.
46
Q

Structures of seeds in angiosperms

A
  • The seed consists of the embryo, endosperm with store food and a seed coat.
  • Seeds are enclosed in the fruit
47
Q

What is parthenocarpy

A

• In some plants fruits develop from the ovary without fertilization. This is called parthenocarpy

48
Q

Features of fruits developed by parthenocarpy

A

Parthenocarpic fruits do not develop seeds.

49
Q

State some plants where parthenocarpy occurs naturally and some other examples where parthenocarpy is induced artificially

A

seeds. Parthenocarpy occurs naturally in some species.
e.g. Banana, pineapple
It also can be induced with plant growth substances to get seedless fruits.
e.g. Grapes, Orange, watermelon

50
Q

Define parthenogenesis

Give examples

A

In some plants, seeds develop without fertilization.
This is called parthenogenesis.

e.g. certain grasses

51
Q

State some ways by which parthenogenesis might occur in plants

A

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

52
Q

State the structures present in seeds

A

Seed coat
Endosperm
Embryo

53
Q

Adaptations seen in seed to survive in land habitat

A
  • seed coat- helps to survive in extreme conditions
  • food reserves-provide nourishment to the embryo during development
  • dormancy period helps to survive during unfavorable conditions
  • adaptations for dispersal give a better chance for growth , development and survival.
54
Q

State 2 functions of seeds

A

Dispersal unit of seed plants

Protects the embryo of the plant

55
Q

2 functions of fruits

A
  • Protects the enclosed seeds

* When mature, aids in their dispersal by wind , water or animals.

56
Q

Define dormancy of a seed

A

• Inhibition of embryo within the seed at one stage of maturation, naturally prevents germination of seeds within fruit, which is called seed dormancy.

57
Q

Mechanisms of inhibiting germination and remain dormant are seen in seeds.
Give some examples

A

• Presence of inhibitors, presence of thick/strong seed coats,
presence of seed coats impervious to water are common causes of seed dormancy.

58
Q

Define germination of seeds

A

• Absorption of water, activation of enzymes, mobilization of food resources (nutrients)
followed by rapid growth process of the embryo
extending radical through the seed coat is called seed germination.

59
Q

Tropic movement shown by the germinating seeds

A

Radical shows positive geotropism and plumule shows negative geotropism.

60
Q

What are the requirements to break dormancy

A

• After breaking seed dormancy, when water, oxygen and suitable temperature are provided, seeds start to germinate.

61
Q

Explain alternation of generations in land plants

A
  • The life cycles of all land plants exhibit alternation of generations, which means the presence of haploid generation and diploid generation alternatively, with each producing the other.
  • The two multicellular body forms that alternate in the life cycles of land plants are the haploid gametophyte and diploid sporophyte which are morphologically different. Therefore called heteromorphic alternation of generations. Their reproductive organs (gametangia and sporangia) are protected by sterile cell layers to prevent desiccation of mother cells. (gamete forming cells and spore forming cells).
  • Gametophytes produce gametes by mitosis.
  • All land plants carryout internal fertilization to prevent desiccation of gametes.
  • Female egg (ovum) is retained in the archegonium and male gametes (antherozoids) are released from the antheridium. Seedless plants depend on external water for fertilization, but seed plants do not depend on external water for their fertilization.
  • 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.
  • Delay of meiosis after fertilization results in creating a diploid sporophytic generation.
  • Diploid sporophyte produces haploid spores by meiosis.
  • Spores grow into haploid gametophytes.
  • 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.

plant Biology (12 decks)

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