Ch. 38: Angiosperm Reproduction and Biotechnology

complete flowers

have all 4 basic floral organs

Seed Dormancy

increases the chances that germination will occur at the time and place most advantageous to the seedling

Stock

provides the root

Coevolution

the joint evolution of 2 interacting species, each in response to selection imposed by the other Ex: the size and shape of a flower correspond with pollen-transporting parts of animals

Method of Pollination

The transfer of pollen from an anther to a stigma is accomplished by wind, water, or animals

The male gametophyte is composed of only two cells. Name each cell, and tell what will come from each of them.

Tube cell: Will produce the pollen tube Generative cell: Will divide and form 2 sperm

Fruit

mature ovary of a flower protects the enclosed seeds and aids in seed dispersal by wind or animals

Flowering

triggered by environmental cues and internal signalling

vegetative propagation

vegetative reproduced facilitated or induced by humans

Self-incompatibility

A plant's ability to reject its own pollen and the pollen of closely related individuals

Each microspore mother cell (microsporocyte) undergoes meiosis to form four haploid

microspores

Seed Development

After double fertilization, each ovule develops into a seed. The ovary develops into a fruit enclosing the seed. When a seed germinates, the embryo develops into a new sporophyte.

Double Fertilization

Fertilization, the fusion of gametes, occurs after the 2 sperm reach the female gametophyte. One sperm fertilizes the egg, forming the zygote. The other sperm combines with 2 polar nuclei, forming a triploid (3n) food-storing endosperm. This double fertilization ensures that endosperm only develops in ovules containing fertilized eggs.

Seed Germination and Seedling Development

Germination depends on imbibition, the uptake of water due to low water potential of the dry seed. Inhibition causes the seed to expand and rupture its coat and triggers changes in the embryo that enable it to resume growth. The radical (embryonic root) emerges first, the developing root system anchors the plant. Next the shoot tip breaks through the soil. In many eudicots, a hook forms in the hypocotyl, and growth pushes the hook above ground. Light causes the hook to straighten and pull the cotyledons and shoot tip up. In monocots, the coleoptile pushes up through the soil surface to create a tunnel for the shoot tip to grow through.

Meiosis in the female part of the plant produces four megaspores. How many survive?

One

Dioecious species

Plants cannot self-fertilize because different individuals have either staminate flowers (lacking carpels) or carpellate flowers (lacking stamens)

Development of Male Gametophytes in Pollen grains

Pollen develops from microspores within the microsporangia or pollen sacs of anthers. Each microspore undergoes mitosis to produce 2 cells: the generative cell and the tube cell. A pollen grain consists of the 2 cells and the spore wall.

Structure of the Mature Seed

The embryo and its food supply are enclosed by a hard protective seed coat. The seed enters a stage of dormancy. The common garden bean consist of two fleshy cotyledons that store food absorbed from the endosperm before the seed germinates. Below where the cotyledons are attached, the embryonic axis is called the hypocotyl, which terminates in the radical (embryonic root). Above the cotyledons is the epicotyl. The plumule consists of the epicotyl, young leaves, and shoot apical meristem. -Eudicot castor beans have thin cotyledons -Monocot maize have one cotyledon -embryo of grass is sheathed with a coleoptile, which covers the young shoot, and the coleorhiza, which covers the young root

Development of Female Gametophytes (embryo sacs)

The embryo sac (female gametophyte) develops within the ovule. Within an ovule, 2 integuments surround a megasporangium. The megasporocyte undergoes meiosis to produce 2 megaspores, only 1 survives. The surviving megaspore divides without cytokinesis, producing 1 large cell with 8 haploid nuclei. The cell is partitioned into a multicellular female gametophyte, the embryo sac.

Embryo Development

The first mitotic division of the zygote splits the fertilized egg into a basal cell and a terminal cell. The basal cell produces a multicellular suspensor, which anchors the embryo to the parent plant. The terminal cell gives rise to most of the embryo. The cotyledons form and the embryo elongate.

What occurs in pollination?

When the pollen grain is transferred to the stigma The pollen tube elongates down the style and the generative cell divides by mitosis to produce 2 sperm

what does a stamen consist of

a filament stalk and an anther, which have chambers called microsporangia to produce pollen

callus

a mass of dividing, undifferentiated totipotent cells that forms where a stem is cut and produces adventitious roots

pistil

a single carpel or 2 or more fused carpels

receptacle

all 4 floral organs are attached to this (carpel, stamen, petal, sepal)

what does a carpel consist of

an ovary, style, and stigma to capture pollen

inflorescences

clusters of flowers

pollen grain

consists of the tube cell, generative cell, and the spore wall

accessory fruit

contains other floral parts in addition to ovaries

simple fruits

develop from a single carpel or several fused carpels

aggregate fruits

develop from a single flower with multiple separate flowers

multiple fruits

develop from an inflorescence, a group of flowers tightly clustered together

Each microspore undergoes mitosis to produce the

haploid male gametophyte

Scion

is grafted onto the stock

incomplete flowers

lacking sepals, petals, stamens, or carpels

asexual reproduction

offspring are derived from a single parent without fusion of egg and sperm, genetically identical offspring

vegetative reproduction (aka asexual reproduction in plants)

offspring arise from mature vegetative fragments from the parent plant

transgenic

organisms that have been engineered to express a gene from another species

another name for microsporangia

pollen sacs

Endosperm Development

precedes embryo development stores nutrients for seedling food reserves are exported to the cotyledons

apomixis (asexual)

the asexual production of seeds from a diploid cell

fragmentation (asexual)

the separation of a parent plant into parts that develop into whole plants (asexual reproduction)

Totipotent cells

those that can divide and asexually generate a clone of the original cell