Plant reproduction and biotechnology

Question 1

Fertilization

Answer 1

The fusion of gametes, results in a diploid zygote, which divides by mitosis and forms a new sporophyte. In angiosperms, the sporophyte is the dominant generation: It is larger, more conspicuous and longer-lived than the gametophyte.

Question 2

Carpels (frugtblade)

Answer 2

Flowers, the reproductive shoots of angiosperm sporophytes, are typically composed of four types of floral organs, carpels, stamens, petals and sepals. Carpels form the first innermost whorl. It’s a reproductive organ and it has an ovary. A flower can have a single carpel, or multiple, depending on the species. In most species, two or more carpels are fused into one structure, and the result is an ovary with two or more chambers.

Question 3

Stamens (støvblad)

Answer 3

Flowers, the reproductive shoots of angiosperm sporophytes, are typically composed of four types of floral organs, carpels, stamens, petals and sepals. Stamens is the second whorl. It’s a reproductive organ.

Question 4

Petals (kronblad)

Answer 4

Flowers, the reproductive shoots of angiosperm sporophytes, are typically composed of four types of floral organs, carpels, stamens, petals and sepals. Petals form the third whorl. It’s sterile. Petals are typically more brightly colored than sepals and advertise the flower to insects and other pollinators.

Question 5

Sepals (bægerblad)

Answer 5

Flowers, the reproductive shoots of angiosperm sporophytes, are typically composed of four types of floral organs, carpels, stamens, petals and sepals. Sepals form the fourth whorl. It’s sterile. Sepals, which enclose and protect unopened floral buds, usually resemble leaves more than the other floral organs do.

Question 6

Receptacle

Answer 6

Carpels, stamens, petals and sepals are all attached to part of the stem called the receptacle. Unlike vegetative shoots, flowers are determinate shoots; they cease growing after the flower and fruit are formed.

Question 7

Ovary (æggestokken)

Answer 7

A carpel has an ovary at it’s base.

Question 8

Style (griffel)

Answer 8

A carpel has a long, slender neck called the style.

Question 9

Stigma (støvfang)

Answer 9

On top of the style, is a sticky structure called the stigma that captures pollen.

Question 10

Ovules

Answer 10

(frøanlægget) Within every ovary is one or more ovules. The number depends on the species.

Question 11

Pistil

Answer 11

The term pistil is sometimes used to refer to a single carpel (a simple pistil) or two or more fused carpels (a compound pistil).

Question 12

Anther (støvknap)

Answer 12

A stamen consists of a stalk called the filaments and a terminal structure called the anther. Within the anther are chambers called microspongia (pollen sacs) that produce pollen.

Question 13

Complete flower

Answer 13

They have all four basic floral organs.

Question 14

Incomplete flower

Answer 14

Some species have incomplete flowers, lacking sepals, petals, stamens or carpels. For example, most grass flowers lack petals. Some incomplete flowers are sterile, lacking functional stamens and carpels. Others are unisexual, lacking either stamens or carpels. Flowers also vary in size, shape, color, odor, organ arrangement, and time of opening.

Question 15

Inflourescences

Answer 15

Some flowers are borne singly, while others are arranged in showy clusters called inflorescences. For example, a daisy is actually an florescence consisting of a central disk composed of hundreds of tiny complete flowers surrounded by sterile, incomplete flowers that look like white petals. Much of floral diversity represents adaptations to specific pollinators.

Question 16

ABC hypothesis

Answer 16

By studying flower mutants, researchers have developed a model called the ABC hypothesis to explain how 3 floral organ identity genes direct the formation of the 4 types of floral organs.

Question 17

Embryo sac (kimsækken)

Answer 17

A female gametophyte, also known as an embryo sac, develops inside each ovule. The process of embryo sac formation occurs in a tissue called the megasporangium within each ovule.

Question 18

Megaspores

Answer 18

Female gametophyte development begins when one cell in the megasporangium of each ovule, the mega sporophyte (or megaspore mother cell), enlarges and undergoes meiosis, producing 4 haploid megaspores. Only one megaspore survives; the others degenerate.

Question 19

Microspores

Answer 19

Within the microsporangia are many diploid cells called microsporocytes, or microspore mother cells. Each microsporocyte undergoes meiosis, forming 4 haploid microspores. Each of which eventually gives rise to a haploid male gametophyte. Each microspore then undergoes mitosis, producing a haploid male gametophyte consisting of only 2 cells: the generative cell and the tube cell.

Question 20

Pollen grain

Answer 20

The generative cell and the tube cell in the microspores and the cell wall, constitute a pollen grain. During maturation of the male gametophyte, the generative cell passes into the tube cell: the tube cell now has a freestanding cell inside it.

Question 21

Spore wall

Answer 21

It consists of material produced by both the microspore and the anther, usually exhibits an elaborate pattern unique to the species.

Question 22

Pollination

Answer 22

After a microsporangium breaks open and releases the pollen, a pollen grain may be transferred to a receptive surface of a stigma, this is the act of pollination.

Question 23

Pollen tube

Answer 23

At the time of pollination, pollen grain typically consists of only the tube cell and the generative cell. It then absorbs water and germinates by producing a pollen tube, a long cellular protuberance that delivers sperm to the female gametophyte.

Question 24

Endosperm

Answer 24

One sperm fertilizes the egg, forming the zygote. The other sperm combines with the two polar nuclei, forming a triploid (3n) nucleus in the centre of the large central cell of the female gametophyte. This will give rise to the endosperm, a food storing seed.

Question 25

Double fertilization

Answer 25

The union of the two sperm cells with different nuclei of the female gametophyte is called double fertilization.

Question 26

Abiotic pollination by wind

Answer 26

Plants that rely on abiotic pollination, use wind or water as their primary pollination agent, and produce neither scent nor nectar, since they don’t need to attract anything.

Question 27

Pollination by insects

Answer 27

About 65% of flowering plants require insects for pollination, even more for major crops. The insects can be bees, moths, butterflies, flies and beetles. Bees are the most important, because they need nectar to make their honey, which means they specifically go from flower to flower. Many flowers like the dandelion have nectar markings (visible under UV light) that help them locate the nectar. Bees like bright colours like yellow and blue, but red is dull to them.

Question 28

Pollination by bats

Answer 28

Bat pollinated flowers are light coloured and aromatic, attracting their nocturnal pollinators.

Question 29

Pollination by birds

Answer 29

Bird pollinated flowers like the columbine flowers, are usually large and bright red or yellow, but they have little to no fragrance since birds don’t have a developed sense of smell. The petals of the flowers are often fused to fit the shape of the birds beak.

Question 30

Coevolution

Answer 30

Many species of flowering plants have evolved with specific pollinators. The joint evolution of two interacting species, each in response to selection imposed by the other, is called coevolution. Natural selection favours individual plants or insects having slight deviations of structure that enhance the flower-pollinator mutualism.

Question 31

Seed

Answer 31

After a successful pollination and double fertilization, a seed begins to form. During this process both the endosperm and the embryo develop. When mature, a seed consists of a dormant embryo surrounded by stored food and protective layers.

Question 32

Dormancy

Answer 32

During the last stages of its maturation, the seed dehydrates until its water content is only about 5-15% of its weight. The embryo, which is surrounded by a food supply (cotyledons, endosperm, or both) enters dormancy, which is it stops growing and its metabolism nearly ceases.

Question 33

Seed coat

Answer 33

The embryo and its food supply are enclosed by a hard, protective seed coat formed from the integruments of the ovule. In some species, dormancy is imposed by the presence of an intact seed coat rather than the embryo itself.

Question 34

Hypocotyl

Answer 34

The embryo consists of an elongate structure, the embryonic axis, attached to fleshy cotyledons. Below where the two cotyledons are attached, the embryonic axis is called the hypocotyl (from the Greek word hypo, under).

Question 35

Radicle

Answer 35

The hypocotyl terminates in the radicle, also called the embryonic root.

Question 36

Epicotyl

Answer 36

The portion of the embryonic axis above where the cotyledons are attached and below the first pair of miniature leaves is the epicotyl, (from the Greek epi, on, over). The epicotyl, young leaves, and shoot apical meristem are collectively called the plumule.

Question 37

Coleoptile

Answer 37

The embryo of a grass seed is enclosed within two protective sheathes: a coleoptile, which covers the young shoot, and a coleorhiza, which covers the young root. Both of these structures aid in soil penetration after germination.

Question 38

Coleorhiza

Answer 38

The embryo of a grass seed is enclosed within two protective sheathes: a coleoptile, which covers the young shoot, and a coleorhiza, which covers the young root. Both of these structures aid in soil penetration after germination.

Question 39

Imbibition

Answer 39

Seed germination is initiated by imbibition, the uptake of water due to the low water potential of the dry seed. Imbibition causes the seed to expand and rupture its coat and triggers changes in the embryo that enable it to resume growth. Following hydration, enzymes digest the storage materials of the endosperm or cotyledons, and the nutrients are transferred to the growing regions of the embryo.

Question 40

Fruit

Answer 40

Before a seed can germinate and develop into a mature plant, it must be deposited in suitable soil. Fruits play a key role in this process. A fruit is the mature ovary of a flower. It protects the enclosed seeds and, when mature, aids in their dispersal.

Question 41

Pericarp

Answer 41

During fruit development, the ovary wall becomes pericarp, the thickened wall of the fruit.

Question 42

Simple fruits

Answer 42

Fruits are classified into several types, depending on their developmental origin. Most fruits are derived from a single carpel or several fused carpels and are called simple fruits, for example peas, lemon and peanuts.

Question 43

Aggregate fruit

Answer 43

An aggregate fruit develops from many separate carpels of one flower, like raspberries, blackberries and strawberries.

Question 44

Multiple fruit

Answer 44

A multiple fruit develops from many flowers that form an inflorescence, for example pineapples and figs.

Question 45

Accessory fruit

Answer 45

An accessory fruit develops largely from tissues other than the ovary. In the apple fruit, the ovary is embedded in a fleshy receptacle.

Question 46

Dispersal by water

Answer 46

Some buoyant seeds and fruits can survive months or years at sea, for instance the coconut, in seed embryo and fleshy white meat (endosperm) are within a hard layer (endocarp), surrounded by a thick and buoyant fibrous husk.

Question 47

Dispersal by wind

Answer 47

Some seeds and fruits are attached to umbrellalike “parachutes” that are made of intricately branched hairs and often produced in puffy clusters. Dandelion seeds (small one-seeded fruits) are carried aloft by the slightest gust of wind.

Question 48

Dispersal by animals

Answer 48

Some seeds have sharp, tack-like spines on the fruits that can pierce tires and injure animals, they are spread by the seed being removed after attaching itself to an animal. Some seeds are in edible fruits that are then eaten, conserved through digestion and pooped out at another location, where it can set up shop. Some seeds are carried by ants because they have food bodies (fødelegemer) that they can eat. Some animals, like squirrels hoard seeds or fruits in underground cache’s, effectively planting them, if the animal dies before retrieving them or forgets where they are.

Question 49

Asexual reproduction

Answer 49

Imagine chopping off your finger and watching it develop into an exact copy of you. If this could actually happen, it would be an example of asexual reproduction, in which offspring are derived from a single parent without fusion of egg and sperm. It is common in angiosperms, and for some species it is the predominant mode of reproduction.

Question 50

Fragmentation

Answer 50

Detached vegetative fragments of some plants can develop into whole offspring, for an example, pieces of a potato with an eye, (vegetative bud) can each regenerate a whole plant. This is fragmentation, the separation of a parent plant into parts that develop into whole plants, is one of the most common modes of asexual reproduction.

Question 51

Apomixis

Answer 51

An entirely different mechanism of asexual reproduction has evolved in dandelions and some other plants. These plants can sometimes produce seeds without pollination or fertilization. The asexual reproduction is called apomixis, (from the Greek word meaning “away from the act of mixing” because there is no joining. A diploid cell in the ovule gives rise to the embryo, and the ovules mature into seeds, which in the dandelion are dispersed by windblown fruits.

Question 52

Vegetative reproduction

Answer 52

Generally, the progeny produced by asexual reproduction are stronger than seedlings produced by sexual reproduction. The offspring usually arise from mature vegetative fragments from the parent plant, which is why asexual reproduction in plants is also known as vegetative reproduction.

Question 53

Dioecious

Answer 53

In the case of dioecious species, plants cannot self-fertilize, because different individuals have either staminate flowers (lacking carpels) or carpellate flowers (lacking stamens).

Question 54

Self-incompatibility

Answer 54

The most common anti-selfing mechanism in flowering plants is self-incompatibility, the ability of a plant to reject its own pollen and the pollen of closely related individuals. If a pollen grain lands on a stigma of a flower of the same or a closely related individual, a biochemical block prevents the pollen from completing its development and fertilizing an egg.

Question 55

Totipotent

Answer 55

In a multicellular organism, any cell that can divide and asexually generate a clone of the original organism is totipotent. Totipotency is found to a high degree in many plants and is generally associated with meristematic tissues. In some plants, however, even differentiated cells can dedifferentiate and become meristematic.

Question 56

Vegetative propagation

Answer 56

Vegetative reproduction occurs naturally in many plants, but it can often be facilitated or induced by humans, in which case it’s called vegetative propagation.

Question 57

Callus

Answer 57

Most houseplants, woody ornamentals, and orchard trees, for example, are asexually reproduced from plant fragments called cuttings. In most cases, shoot cuttings are used. At the cut end of the shoot, a mass of dividing, undifferentiated cells called a callus forms, and adventitious roots then develop from the callus. If the shoot fragment includes the node, then adventitious roots form without the callus stage.

Question 58

Stock

Answer 58

In grafting, a twig or a bud from one plant is joined to a plant of a closely related species or a different variety of the same species. Grafting makes it possible to combine the best qualities of different varieties or species into a single plant. The plant that provides the root system is called the stock.

Question 59

Scion

Answer 59

In grafting, a twig or a bud from one plant is joined to a plant of a closely related species or a different variety of the same species. Grafting makes it possible to combine the best qualities of different varieties or species into a single plant. The twig grafted onto the stock is referred to as the scion.

Question 60

Transgenic

Answer 60

With genetic engineering, gene transfers can be done quickly, more specifically, and without the need for intermediate species. The term transgenic is used to describe organisms that have been engineered to express a gene from another species.

Question 61

Biofuels

Answer 61

Many scientists predict that biofuels, fuels derived from living biomass, could produce a sizable fraction of the worlds energy needs in the not to distant future.

Question 62

Biomass

Answer 62

Biomass is the total mass of organic matter in a group of organisms in a particular habitat. The use of biofuels from plant biomass would reduce net emission of CO2. It would be carbon neutral.