IB BIOLOGY Topic 9: Plant Biology

Xylem

The tissue in plants responsible for transporting water and minerals from the roots to the rest of the plant.

Transpiration

The process by which water evaporates from the leaves of a plant, creating a pull that helps transport water and minerals through the xylem.

Vessel Elements/Members

Dead hollow cells in the xylem that transport water and solutes, with perforated end walls allowing for easy passage of water between cells.

Tracheids

Dead conducting cells in the xylem that are smaller in diameter than vessel elements, with tapered ends and pits for side-to-side conduction.

Fibers

Long, slender cells in the xylem that provide mechanical support and strength to the plant.

Parenchyma

Thin-walled living cells in the xylem that play a role in storage, metabolism, tissue repair, and regeneration.

Phloem

The tissue in plants responsible for transporting sugars and other organic compounds from the leaves to other parts of the plant.

Sieve Tube Elements/Members

Specialized parenchyma cells in the phloem that lack a nucleus and many other cellular components, connected by sieve plates and under positive pressure.

Companion Cells

Cells adjacent to sieve tube elements in the phloem that help coordinate their function and support their metabolic processes.

Seeds

Reproductive structures produced by plants, containing an embryo, seed coat, and endosperm, which can remain dormant until conditions are favorable for germination.

Dormancy

A period of growth inactivity in seeds, during which they remain viable but do not germinate. Different species have different requirements to break dormancy.

Germination

The process of initiating embryonic growth in a seed, resulting in the emergence of shoot and root structures.

Meristems

Regions of actively dividing cells in plants that contribute to primary growth and the initiation of new organs or branches.

Apical Meristem

Meristems located at the tips of roots and shoots, responsible for primary growth and the development of new tissues.

Intercalary Meristem

Meristems that occur between mature tissues, often at the bases of grass leaf blades, contributing to leaf elongation.

Lateral Meristem

Meristems responsible for secondary growth, increasing the width or girth of plant structures.

Reproduction

The process by which plants propagate and ensure the survival of their species. It includes both sexual and asexual mechanisms, such as vegetative reproduction.

Asexual Reproduction

The ability of plants to produce new individuals from vegetative parts such as stems, leaves, or roots without the involvement of gametes.

Succulent Plants

Plants, like cacti, that have the ability to reproduce asexually by growing a new plant from a detached segment of their stem.

Runners

Horizontal stems sent out by plants like strawberries that can develop into new plants by establishing roots and growing independently.

Rhizomes

Horizontal underground stems with short internodes that are thickened for storage.

Stolons

Horizontal stems, either aboveground or underground, with longer internodes and smaller diameter that can produce asexual plantlets.

Tubers

Modified part of a stolon that is used for storage, such as potatoes.

Sexual Reproduction

The process of plant reproduction involving the fusion of male and female gametes.

Flower Anatomy

Complex structures in sexually reproducing plants that contain both male and female reproductive organs.

Pollination

The transfer of pollen from the anther to the stigma, which can occur through various mechanisms such as wind, insects, birds, or other animals.

Double Fertilization

A unique reproductive feature in flowering plants where one sperm cell fuses with an egg cell to form an embryo, while another sperm cell combines with polar nuclei to create endosperm.

Seed Formation

The development of a seed from the fertilized ovule, which contains the embryo, endosperm, and a protective seed coat.

Fruit Development

The maturation of the ovary into a fruit, which protects and aids in the dispersal of seeds.

Germination

The process by which a seed begins to grow and develop into a new plant.

Imbibition

The uptake of water through the seed coat, initiating metabolic processes within the seed.

Emergence of the Radicle

The first structure to emerge from the seed, the embryonic root, which anchors the plant and absorbs water and nutrients from the soil.

Shoot Growth

The emergence of the plumule, containing the embryonic shoot, which develops into the stem and leaves of the new plant.

Temperature and Light

Environmental factors that can influence germination, as some seeds require specific temperature or light conditions to trigger germination.

Seed Dormancy

A period of growth inactivity in certain seeds that allows them to survive adverse conditions, which can be broken by scarification, exposure to smoke compounds, or temperature fluctuations.

Hormones

Chemical messengers like gibberellins that regulate seed germination by stimulating embryo growth and mobilizing stored energy reserves in the endosperm.