Biology: Self-Pollination vs Cross-Pollination

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Questions and Answers

What is the main function of the stem in a plant?

Root development

Support

Conduction of water, food materials, and mineral nutrients (correct)

Photosynthesis

What type of stem modification is characterized by underground storage?

Climbing

Perennation or storage (correct)

Vegetative propagation

Support in special habit

What is the term for a stem that grows upward with the aid of tendrils?

Trailing

Decumbent

Twining

Climbing (correct)

What is the term for a stem that grows along the ground and roots at the nodes?

Decumbent Signup and view all the answers

What is the term for a stem that grows in a zigzag pattern?

Dichotomous Signup and view all the answers

What is the term for a stem that grows upright and has a stout stem?

Columnar Signup and view all the answers

What is the term for a stem that coils around an object for support?

Twining Signup and view all the answers

What is the term for a stem that sprawls across objects?

Clambering Signup and view all the answers

What is the primary reason why self-pollination is used in hybridisation experiments?

To maintain purity of the race Signup and view all the answers

What is the consequence of prolonged self-pollination?

Vigour and vitality of the race decreases Signup and view all the answers

What is the primary factor that encourages cross-pollination?

All of the above Signup and view all the answers

What is the advantage of cross-pollination in terms of genetic variation?

It generates genetic variation Signup and view all the answers

What is the disadvantage of cross-pollination in terms of character inheritance?

Undesirable characters may creep in the race Signup and view all the answers

What is the primary benefit of cross-pollination in terms of adaptability?

It increases adaptability to changed environment Signup and view all the answers

What is the consequence of cross-pollination in terms of pollination?

It is a factor of chance in pollination Signup and view all the answers

What is the characteristic of plants produced through cross-pollination?

They are more resistant to diseases Signup and view all the answers

What is the characteristic feature of the main axis of inflorescence in a Cymose type of inflorescence?

It terminates into a flower Signup and view all the answers

Which type of inflorescence has flowers that grow in basipetal succession?

Cymose Signup and view all the answers

What is the term for an unbranched inflorescence with pedicel flowers?

Simple Raceme Signup and view all the answers

What is the function of the ovary in an angiosperm flower?

To enclose the ovules Signup and view all the answers

What is the term for an inflorescence with sessile flowers?

Spadix Signup and view all the answers

What is the outermost part of an angiosperm flower?

Calyx Signup and view all the answers

What is the primary function of the part of the plant body that grows downwards into the soil?

Anchorage and Absorption of water and inorganic salt solutions Signup and view all the answers

Which type of root modification is characterized by fleshy and swollen structures, such as those found in Ipomoea batatas?

Tuberous root Signup and view all the answers

What is the term for the arrangement of flowers on the flowering axis?

Inflorescence Signup and view all the answers

Which type of root modification is found in Zea mays and Ficus sp, and provides support to the stem?

Prop root Signup and view all the answers

What is the term for the type of root that grows from other parts of the plant body, such as stems or leaves?

Adventitious root Signup and view all the answers

Which type of root modification is found in Arachis hypogea and is involved in nitrogen fixation?

Nodulated root Signup and view all the answers

What is the term for the type of root that is conical in shape and found in plants such as Daucus carota?

Conical root Signup and view all the answers

Which type of root modification is found in Vanda and is involved in water absorption?

Hygroscopic root Signup and view all the answers

What is a characteristic of pollen grains in entomophilous flowers?

They are spiny and surrounded by a yellow oily sticky substance called pollenkit Signup and view all the answers

What is a characteristic of flowers that are pollinated by birds?

They are brightly coloured and have abundant nectar Signup and view all the answers

What is the term for the transfer of pollen grains through insects?

Entomophily Signup and view all the answers

What is a characteristic of stigma in entomophilous flowers?

It is long and sticky Signup and view all the answers

What is the term for the process of fruit formation without fertilization?

Parthenocarpy Signup and view all the answers

What type of fruit is a pome?

Simple fleshy fruit Signup and view all the answers

What is the term for a fruit that comes from multiple ovaries in a single flower?

Multiple fruit Signup and view all the answers

What is the term for a fruit that comes from a single ovary in a flower?

Simple fruit Signup and view all the answers

Study Notes

Pollination

Self-pollination is used to maintain pure lines for hybridization experiments and to reduce vigour and vitality of the race.
Cross-pollination occurs in the presence of an external agent, also known as Allogamy or Xenogamy, and generates genetic variation through mating with others (outcrossing).
Factors that encourage cross-pollination include dioecy, heterostyly, distyly, tristyly, dichogamy, and self-incompatibility.

Advantages and Disadvantages of Cross-Pollination

Advantages:
- Introduces genetic recombination and variation in the progeny.
- Increases adaptability of the offspring towards changes in the environment.
- Makes the organisms better fitted in the struggle for existence.
Disadvantages:
- A factor of chance is always involved in cross-pollination.
- It is less economical.
- Undesirable characters may creep in the race.

Stem

The stem is the ascending axis of the plant body, consisting of nodes and internodes, leaf scars, buds, and lenticels.
Functions of the stem include conduction of water, food materials, and mineral nutrients, support, storage, and sometimes photosynthesis.

Types of Stem

Based on direction of growth/position:
- Ascending
- Erect
- Columnar
Based on habit:
- Dichotomous (branched stem)
- Erasmous (unbranched stem)
- Fruticose (shrubby)
- Arborescent (tree-like in appearance and size)
- Twining (coiling around object)
- Climbing (growing upward with the aid of tendrils)

Modifications of Stems

Under-ground stems (perennation or storage):
- Rhizomes (e.g., Colocasia esculenta, Zingiber officinale)
- Corms (e.g., Crocus sp)
- Turions (e.g., Saggitarius sp)
Sub-aerial stems (vegetative propagation):
- Runners (e.g., Oxalis)
- Offsets (e.g., Pistia stratioites)
- Suckers (e.g., Ananas comosus)
- Stem tubers (e.g., Solanum tuberosum, Dioscorea alata)
Aerial stems (support in special habit):
- Climbers (e.g., Paullinia pinnata)
- Twiners (e.g., Vigna unguiculata)
- Tendrils (e.g., Luffa aegyptiaca)

Roots

Function primarily in anchorage, absorption of water and inorganic salt solutions, reproduction, and aeration.

Types of Roots

Primary root (the first root of a germinating seed)
Secondary/Lateral roots (branches from primary root)
Tap root
Fibrous root
Adventitious root (grows from other parts of the plant body)

Modifications of Roots

Storage:
- Tuberous (e.g., Ipomoea batatas)
- Conical (e.g., Daucus carota)
- Fusiform (e.g., Radish)
- Napiform (e.g., Beta vulgaris)
- Fasciculate (e.g., Asparagus)
Support:
- Prop root (e.g., Zea mays, Ficus sp)
- Stilt (e.g., Rhizophora racemosum)
- Buttress (e.g., Milicia excelsia, Ceiba petandra)
Physiological function:
- Nodulated (e.g., Arachis hypogea)
- Pneumatophore (e.g., Avicennia germinas)
- Hygroscopic (e.g., Vanda)
- Assimilatory (e.g., Trapa)
- Sucking/Haustoria (e.g., Dodder)
- Mycorrhizal (e.g., Monotropa)

Inflorescences

Flowering shoot with an arrangement of flowers on the flowering axis.
Types of inflorescences:
- Based on mode of branching:
  - Indefinite or indeterminate or Racemose
  - Definite or determinate or Cymose
- Based on the presence or absence of pedicel:
  - Sessile flowers
  - Pedicel flowers (unbranched, branched, or compound)

Flowers

Highly modified spore-bearing shoot.
Consists of an axis called Receptacle, with ovules enclosed in the ovary.
Primarily functions in reproduction.

Parts of Angiosperm Flower

Pedicel
Receptacle
Epicalyx (sometimes present)
Calyx (sepals, green or petalloid)
Corolla (petals, usually brightly colored)

Entomophily

Pollination through insects.
Characters:
- Showy or brightly colored flowers
- Landing platform for insects
- Pollen grains are spiny, heavy, and surrounded by a yellow oily substance
- Stigmas are often inserted and sticky
- Some flowers provide a safe place for insects to lay eggs

Ornithophily

Pollination through birds.
Characters:
- Brightly colored flowers
- Floral parts are commonly leathery
- Flowers secrete abundant watery nectar or have edible parts
- Scent is often absent

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Description

Compare the characteristics and consequences of self-pollination and cross-pollination in plants, including effects on race purity, vigour, immunity, and adaptability.