Plants

• Plants are multicellular, eukaryotic organisms that belong to the kingdom Plantae. 

• They are characterized by their ability to perform photosynthesis, a process by which they convert light energy into chemical energy stored in the form of carbohydrates. 

• Plants play a crucial role in the Earth's ecosystems, providing oxygen, food, and habitat for many organisms.

1. Roots:

Function: Anchoring the plant in the soil, absorbing water and minerals.

Structure: Typically underground, with root hairs increasing surface area for absorption.

2. Stems:

Function: Support, transport of water, minerals, and sugars between roots and leaves.

Structure: Varies (herbaceous or woody), contains vascular bundles for transport.

3. Leaves:

Function: Site of photosynthesis, gas exchange (through stomata), and transpiration.

Transpiration - when plants take up liquid water from the soil and release water vapor into the air from their leaves

Structure: Epidermis, mesophyll cells, and veins containing xylem and phloem.

Epidermis - outermost layer of leaf (regulation of gas exchange)

• consists of the upper and lower epidermis, which are present on either side of the leaf.

  • adaxis (adaxial surface) - the upper side

  • abaxial (abaxial surface) - the lower side

Mesophyll cells - internal ground tissue located between the two epidermal cell layers of the leaf (aids in gas exchange and photosynthesis via chloroplasts)

The leaf contains vascular bundles composed of xylem and phloem.

• A single vascular bundle, no matter how large or small, always contains both xylem and phloem tissues.

  • xylem consists of tracheids and vessels, which transport water and minerals to the leaves.

  • phloem transports the photosynthetic products from the leaf to the other parts of the plant.

Tip (Leaf apex) - is the tip or protruding part of the leaf.

• The leaf apices can vary in shapes and sizes in different plants.

Midrib - commonly found at the back part of the leaf, which becomes the storage of the stomata.

Lamina - entire flat and extended section of the leaf (blade of the leaf)

Margin - even and smooth around the entire leaf edge.

Veins - small channels or capillaries that transport water and minerals to and from the leaf of a plant.

Petiole - the stalk that joins the blade (the flat part of the leaf, also called a lamina) to the node (the attachment point on a stem).

4. Flowers:

Function: Reproduction; production of seeds and fruits.

Structure: Sepals, petals, stamens (male), and carpels (female).

Sepals - outer parts of the flower (often green and leaf-like) that enclose a developing bud

Petal - parts of a flower that are often conspicuously colored

Receptacle - the part of a flower stalk where the parts of the flower are attached.

Carpels - female reproductive structures that produce egg cells and protect a developing baby plant, or embryo

• Stigma - part of the female reproductive system of a flower. It is found in the center of a flower and helps to collect pollen.

• Style - the stalk that supports the stigma and connects it to the ovary.

  • one major function is to assist with fertilization by being the location where pollen tubes travel to deliver sperm cells to the egg.

• Pollen Tube - to deliver sperm cells to the female gametophyte for double fertilization

• Ovary - enlarged basal portion of the pistil, the female organ of a flower.

  • The ovary contains ovules, which develop into seeds upon fertilization.

  • The ovary itself will mature into a fruit, either dry or fleshy, enclosing the seeds.

• Ovule - the organ that forms the seeds of flowering plants.

Stamens - male reproductive structures that produce pollen

• Anther - part of the stamen where pollen is produced

• Filament - a stalk-like structure that attaches to the base of the flower and supports the anther, which is the structure that produces pollen.

5. Stomata:

Function: Regulate gas exchange (carbon dioxide in, oxygen out) and reduce water loss.

Structure: Small openings on the leaf surface, primarily on the underside.

6. Xylem and Phloem:

Function: Transport of water and nutrients (xylem) and sugars (phloem) throughout the plant.

• The xylem distributes water and dissolved minerals upward through the plant, from the roots to the leaves.

• The phloem carries food downward from the leaves to the roots.

Structure: Xylem has lignified (woody) cells for strength, while phloem consists of sieve tubes. (component of the phloem in plants. They function as the vessel that transports organic food and other material across the plant).

7. Meristems:

Function: Regions of actively dividing cells, responsible for growth and development.

Structure: Apical meristems at the tips of roots and shoots, lateral meristems for secondary growth.

8. Chloroplasts:

Function: Contain chlorophyll for photosynthesis, converting light energy into chemical energy.

Structure: Double membrane with thylakoid stacks.

• Outer membrane - contains porins and is therefore freely permeable to small molecules.

• Inner membrane - is impermeable to ions and metabolites, which are therefore able to enter chloroplasts only via specific membrane transporters.

• Thylakoids - an internal system of interconnected membranes, that carry out the light reactions of photosynthesis

  • They are arranged into stacked and unstacked regions called grana and stroma thylakoids, respectively, that are differentially enriched in photosystem I and II complexes.

• Stroma - the liquid material found throughout the cavity of the chloroplast.

  • The function of the stroma is to provide volume around the different structures inside the chloroplast for protection.

  • The stroma is where the light-independent reaction process of photosynthesis, also called the carbon cycle, takes place.