Lecture Slides

• Plant organs are composed of tissues, which in turn are composed of cells.
• A cell is the fundamental unit of life.
• A tissue is a group of cells consisting of one or more cell types that together perform a specialized function.
• An organ consists of several types of tissues that together carry out particular functions.
• The root system anchors the plant and takes in water and nutrients from the soil.
• The shoot system harvests light and carbon dioxide from the atmosphere to produce sugars.
• Together, these systems make up the plant body.
• Many root systems have a taproot and lateral roots.
• Roots anchor the plant, absorb ions and water from soil, conduct water and ions to the shoot system, obtain energy from the sugar in the shoot system, and store molecules produced in the shoot system.
• Roots are possible association with mycorrhizal fungi or nitrogen fixing bacteria.
• Stems consist of nodes, where leaves are attached, and internodes, or segments between nodes.
• Axillary (or lateral) buds form at nodes just above the site of leaf attachment.
• Water and minerals are pulled up from the roots by negative pressure generated by evaporation from leaves, a process known as transpiration.
• Cork cambium is located near the outer perimeter of the root, trunk, or branch.
• Vascular cambium also produces sclerenchyma fibers and parenchyma cells, formed in lateral rows of cells called rays.
• The older, innermost secondary xylem accumulates protective compounds (resins/gums) in a tree trunk.
• Dark-colored, inner xylem (heartwood), and light-colored, outer xylem (sapwood) are present in a tree trunk.
• Gas exchange occurs through small openings called lenticels in the bark of a tree trunk.
• Production of these tissues is highly asymmetrical with creation of more secondary xylem, which is retained and accumulates as wood.
• Cork cambium produces cork cells to the exterior of the trunk, forming the bark of a tree trunk.
• In areas with seasonality, the vascular cambium stops growing during the dry or cold season, resulting in the formation of annual tree rings, with alternating early and late wood.
• Vascular cambia in roots and stems produce the secondary xylem and secondary phloem, which make up wood and the inner part of the tree’s bark respectively.
• An axillary bud may grow into a branch.
• Xylem transports water and minerals from roots to shoots.
• The tip of each stem and branch contains an apical bud.
• Apical and axillary buds may develop into flowers.
• Sugars are pushed by positive pressure from where they are produced or stored to where they are needed, a process known as phloem transport.
• Water is pulled up xylem.
• Water moves from soil into root.
• Water is pulled out of xylem.
• Water is pulled out of root cortex.
• Shoot systems range in size from the tiniest duckweed (5 mm in diameter) to the giant Sequoia (100 ft in diameter and 300 ft tall).
• After water is absorbed through a root hair, it travels through the root cortex toward the vascular tissues via one of three routes: the symplastic route, the transmembrane route, or the apoplastic route.
• Shoot systems can have different shapes, allowing competition for light.
• Simple leaves have a petiole and a single blade.
• Compound leaves have blades divided into leaflets.
• In essence, water can flow through the symplast via plasmodesmata, through cells via aquaporins, or through the apoplast via the spaces between cells.
• Doubly compound leaves are large yet rarely damaged by wind or rain.
• The Casparian strip has cell walls impregnated with suberin and blocks the apoplastic pathway at the endodermis.
• Needlelike leaves are characteristic of species adapted to very cold or hot climates.