Vegetative Organs of the Flowering Plant Body Most flowering plants belong to one of two major lineages. Monocots are generally narrow-leaved flowering plants such as grasses. Eudicots are broad-leaved flowering plants such as roses. Monocots and eudicots account for 97 percent of the species of flowering plants.

Figure 35.1 Monocots versus Eudicots

Vegetative Organs of the Flowering Plant Body The shoot system of a plant consists of the stems and the leaves, as well as flowers. Leaves are the main sites of photosynthesis in plants. Stems hold and display the leaves to the sun and provide connections for the transport of materials between roots and leaves. A node is the point where a leaf attaches to a stem. Regions of stem between nodes are the internodes. The root system provides support and nutrition.

Figure 35.2 Vegetative Organs and Systems

Vegetative Organs of the Flowering Plant Body There are two main types of root system: taproot and fibrous root. Most eudicots have a taproot system.. Monocots and some eudicots have a fibrous root system.

Figure 35.3 Root Systems

Vegetative Organs of the Flowering Plant Body A bud is an embryonic shoot. A stem bears leaves at its nodes, and where each leaf meets the stem, there is a lateral bud. At the tip of each stem or branch there is an apical bud, which produces the cells for the growth and development of that stem or branch.

Vegetative Organs of the Flowering Plant Body Leaves are well adapted for gathering light. The blade of a leaf is a thin, flat structure, attached to the stem by the petiole. A simple leaf has a single blade. A compound leaf has multiple blades (or leaflets) arranged along an axis or radiating from a central point.

Figure 35.5 The Diversity of Leaf Forms

Plant Cells Plant cells have all the organelles common to eukaryotes. Every plant cell is surrounded by a cellulose- containing cell wall.

Plant Cells On division each daughter cell secretes cellulose and other polysaccharides to form a primary wall. Some plant cells may deposit more layers, sometimes impregnated with material such as lignin or suberin to form a secondary wall.

Figure 35.6 Cell Wall Formation

Plant Cells Plasmodesmata are pore-like structures that pass through primary cell walls, allowing substances to move freely from cell to cell without crossing the plasma membrane. Animal Cells have similar structures called gap junctions.

Figure 35.7 Plasmodesmata (Part 2)

Plant Cells Parenchyma cells are the most numerous type of cell in young plants. Parenchyma cells usually have thin walls and large central vacuoles. The photosynthetic cells in leaves are parenchyma cells filled with chloroplasts. Some parenchyma cells store lipids or starch.

Plant Cells Collenchyma cells are supporting cells that lay down primary cell walls that are thick in the corners. Collenchyma cells provide support to leaf petioles, nonwoody stems, and growing organs.

Plant Cells Sclerenchyma cells are the main supporting cells of a plant. There are two types of sclerenchyma cells: fibers and sclereids. Sclereids form the grit found in many fruits like pears.

Figure 35.9 Plant Cell Types (Part 1)

Figure 35.9 Plant Cell Types (Part 2)

Plant Cells The xylem conducts water from roots to above ground plant parts. It contains conducting cells called tracheary elements, Tracheids and Vessel elements. Both tracheary elements and tracheids undergo apoptosis and do their jobs as empty cells (only the cell walls remain).

Figure 35.10 Evolution of the Conducting Cells of Vascular Systems

Plant Cells Cells of the phloem are alive when they do their job, unlike those of the xylem. The characteristic cell of the phloem is the sieve tube member. The sieve tube members have adjacent companion cells. Companion cells retain all their organelles and may regulate the performance of the sieve tube members.

Plant Tissues and Tissue Systems A tissue is an organization of cells that work together as a functional unit. Parenchyma cells make up parenchyma tissue, which is a simple tissue. Xylem and phloem are complex tissues; they are composed of a number of different cell types. Tissues are grouped into tissue systems that extend throughout the body of the plant from organ to organ. There are three plant tissue systems: vascular, dermal, and ground.

Plant Tissues and Tissue Systems The vascular tissue system includes the xylem and phloem; it is the conductive or “plumbing” system of the plant. The phloem transports carbohydrates from sites of production (sources such as leaves) to sites of utilization (sinks) elsewhere in the plant. The xylem distributes water and mineral ions taken up by the roots to the stem and leaves.

Plant Tissues and Tissue Systems The dermal tissue system is the outer covering of the plant. The epidermis contains epidermal cells and other specialized cells such as guard cells. The shoot epidermis secretes a layer of wax- covered cutin, the cuticle, which helps retard water loss from stems and leaves.

Plant Tissues and Tissue Systems The ground tissue system makes up the rest of a plant and consists primarily of parenchyma tissue. Ground tissue functions primarily in storage, support, and photosynthesis.

Forming the Plant Body In animals, the body grows as an individual develops from embryonic stages but ceases to grow once adulthood is reached (determinate growth). In plants the growth of roots and stems is indeterminate and is generated from specific regions of active cell division.

Forming the Plant Body The localized regions of cell division in plants, called meristems, are forever embryonic. They have the ability to produce new cells indefinitely. The cells of meristematic tissues are analogous to the stems cells found in animals.

Forming the Plant Body There are two types of meristems: Apical meristems give rise to the primary plant body, which is the entire body of many plants. Lateral meristems give rise to the secondary plant body.

Forming the Plant Body Shoot apical meristems supply the cells that extend stems and branches. Root apical meristems supply the cells that extend roots. Apical meristems are responsible for primary growth, which leads to elongation and organ formation.

Forming the Plant Body Vascular cambium produces the secondary xylem and phloem. The cork cambium produces cells that protect the outermost layers of the stem.

Forming the Plant Body The root cap protects the delicate growing area of the root as it pushes through the soil. The root cap also detects the pull of gravity and controls the downward growth of roots. Tissues of the root are divided into three zones: cell division, cell elongation, and cell differentiation.

Forming the Plant Body Vascular tissue in the stem is arranged in vascular bundles. The eudicot stem also contains pith and cortex storage tissues.

Leaf Anatomy Supports Photosynthesis Leaf anatomy is adapted to carry out photosynthesis, limit evaporative water loss, and transport the products of photosynthesis to the rest of the plant. The two zones in leaf parenchyma that photosynthesize are the palisade mesophyll and the spongy mesophyll. Within the mesophyll is air space through which CO2 can diffuse to the photosynthesizing cells.

Figure 35.23 (a) The Eudicot Leaf

Leaf Anatomy Supports Photosynthesis Veins supply mesophyll cells with water and minerals, and they transport the products of photosynthesis to the rest of the plant. The epidermis of the leaf is the outermost cell layer, which is covered by a waxy cuticle. The epidermis functions to keep water and photosynthetic products in the leaf. Guard cells allow controlled gas exchange through pores in the leaf (the stomata).

Figure 35.23 (b,c) The Eudicot Leaf