Question

A seed is a. an embryo produced by the fertilization of an egg, which is protected by a seed coat. b. a structure that germinates to form a seedling under the right conditions. c. an embryo produced by parthenogenesis that is enclosed by a seed coat. d. all of the above. e. none of the above.

Short answer

The correct answer is 'd. all of the above'.

Step-by-step solution

Identification

Identify the various definitions given in the options.

Evaluation

Evaluate each definition against your understanding of what a seed is. A comprehensive knowledge of seed biology would be helpful. A seed is a fertilized, mature ovule containing an embryo. It is formed from fertilization, not parthenogenesis, and it is indeed protected by a seed coat. Furthermore, it certainly does have the ability to germinate into a seedling given the right conditions.

Selection

Select the definition(s) that correctly defines a seed. Here definition a and b both define characteristic features of a seed, therefore, the correct answer is 'd. all of the above' as it contains all correct points.

Key concepts

Seed Biology

Understanding the biology of a seed is fundamental in grasping how plants reproduce and continue their species. A seed encompasses an embryo, which is a vital component as it develops into a new plant. This embryo is the result of the fertilization of an egg within the ovule of the parent plant. Along with the embryo, the seed contains a nutrient-rich tissue called endosperm, which provides sustenance during early growth.

Protected by a tough outer covering known as the seed coat, the seed is equipped to withstand various environmental conditions until it finds the appropriate conditions to germinate. Seeds differ vastly in size, shape, and how they disperse, but their primary purpose is uniform across plant species: to ensure the survival and propagation of the plant's genetic material.

Seed Germination

Seed germination is the process through which a seed develops into a new plant. This phase marks the beginning of a seedling's life cycle and requires specific conditions to be triggered. Generally, these include the right temperature, sufficient moisture, adequate oxygen, and, in some cases, light.

Once these conditions are met, the seed absorbs water, causing it to swell and break through the seed coat in an event known as imbibition. Subsequent steps involve the growth of a root (radicle) downward into the soil and a shoot (plumule) upward towards the light. These first growths utilize the nutrients stored within the endosperm until the plant can photosynthesize and obtain energy from the sun. Each step of germination is a delicate dance of growth, energy use, and environmental adaptation.

Embryo Development

Embryo development within a seed is a fascinating aspect of plant reproduction. After fertilization, the zygote undergoes numerous cell divisions and begins to form the structures that will eventually constitute the mature plant. This development occurs in stages, starting with the formation of the basic body plan including the embryonic root (radicle), stem (hypocotyl), and leaves (cotyledons).

As the embryo matures, it enters a period of dormancy, during which time it is unresponsive to germination cues. This dormancy allows the seed to survive adverse conditions until the environment is favorable for growth. The transition from a dormant embryo to an active one ready for germination is a key step in the plant's lifecycle and is highly regulated by both internal and external signals.

Sexual Reproduction in Plants

Sexual reproduction in plants occurs through a process known as pollination, where pollen from the male structure of a plant (stamen) is transferred to the female structure (pistil). Once fertilization takes place, the ovule, which contains the egg, develops into a seed. This seed is a packet of genetic information from two parent plants, and it's equipped to develop into a new, genetically unique organism.

Plant sexual reproduction ensures genetic diversity, which is critical for plant populations to adapt to changing environments and resist diseases. Unlike asexual reproduction where offspring are clones of the parent, sexual reproduction in plants fosters the recombination of genetic material, leading to varied traits among offspring, which may enhance their survival.