Pollination and Double Fertilization

Flashcards covering key vocabulary terms related to pollination, double fertilization, seed development, and dormancy from the lecture notes.

Pollination

The transfer of pollen from the anther to the stigma.

Biotic Pollination

Pollination aided by animals and insects (occurs in 20% of plants).

Abiotic Pollination

Pollination aided by non-living factors like wind or water.

Wind Pollination

Pollen transfer by wind (accounts for 98% of abiotic plants).

Water Pollination

Pollen transfer by water (accounts for 2% of abiotic plants).

Pollen

A reward for animal pollinators, rich in protein (15-30%), sugar (15%), fat, and starch.

Nectar

A reward for animal pollinators, rich in sugar (15-75%), all 13 amino acids, and lipids.

Nectarguides

Visual cues in flowers that guide pollinators to nectar (present for bees, butterflies).

Microsporocyte

A cell that undergoes meiosis to form four haploid microspores during pollen development.

Pollen Grain (Two-celled)

Consists of a tube cell and a generative cell, formed from a microspore nucleus division.

Double Fertilization (Germination)

The process where a pollen grain lands on the stigma and forms a pollen tube down the style to the ovule.

Double Fertilization (Entry)

The pollen tube penetrates the micropyle, digests a synergid cell, and releases two sperm into the embryo sac.

Syngamy

The fusion of one sperm cell with one egg cell to form a diploid (2n) zygote.

Triple Fusion

The fusion of the second sperm cell with the polar nuclei in the embryo sac to form a triploid (3n) endosperm.

Outcome of Double Fertilization

A 2n zygote develops, protected and nourished by the 3n endosperm.

Self-pollination (Selfing)

Transfer of pollen from an anther to a stigma on the same plant or even the same flower.

Inbreeding Depression

Reduced fitness in offspring due to low amounts of heterozygous alleles, often resulting from self-pollination.

Cross-pollination (Outcrossing)

Transfer of pollen from one plant to another plant.

Dioecious Plants

Plants that cannot self-pollinate because individual plants have either male or female flowers, but not both.

Heterostyly (Heteromorphic Incompatibility)

A mechanism to prevent self-pollination where flowers have different carpel and stamen lengths, making pollen incompatible with its own flower.

Genetic Incompatibility (S gene)

A gene that allows plants to recognize and reject self-pollen, preventing self-fertilization.

Gametophytic Pollen Incompatibility

Pollen has a surface protein that must not match an allele on the stigma; otherwise, the pollen tube will not grow.

Sporophytic Pollen Incompatibility

Pollen has two proteins on its surface that must not match those of the stigma to allow pollen tube growth.

Seeds

The result of a successful fertilization event, consisting of an embryo and nutrients surrounded by a protective coat.

Imbibition

The uptake of water by seeds, critical for germination as seeds are typically only 5-10% water.

Germination

The appearance of the radicle and shoot from a seed, often visibly marked by a swollen radicle.

Emergence

The appearance of a seedling shoot above the ground.

Epigeal Germination

A type of germination where the cotyledons emerge above ground.

Hypogeal Germination

A type of germination where the cotyledons or storage structures remain below ground.

Physiological Dormancy

Dormancy broken by environmental cues such as light, temperature, or water.

Physical Dormancy

Dormancy caused by a seed coat that is impermeable to water, often requiring mechanical breaking (e.g., passage through animals, freezing-thawing).