Introduction to Plant Structure and Growth IB Topic 9.1
Jan 02, 2016
Starting Points
• Green plants are autotrophic• Green plants show wide diversity: mosses
(bryophytes), ferns (filicinophytes), conifers (coniferophytes), and flowering (angiosperms)
• Photosynthesis • Green plants manufacture carbohydrates from
CO2 and water; energy is the waste product • Light dependent (grana) • Light independent (stoma)
Plants
• Green plants (Plantae) make up one of the 5 kingdoms of living things
• Characteristics• There is a wall around each cell; chief component
is cellulose (polysaccharide, extremely tough and protective material)
• Chloroplasts (site of …?) • Green plants evolved about 500 million years
ago from aquatic, single celled algae (Chlorella). Today angiosperms are the most dominant terrestrial plants.
Plant Structure and Growth
• Whether wood or herbaceous (non-woody), plants consist of stem, leaves, and root
Stem
• The stem supports the leaves in the sunlight, and transports organic materials (such as sugar and amino acids), ions, and water between the roots and leaves.
• At the top of the stem is a terminal bud or terminal growing point
• In the axil of each leaf is an axillary bud• New cells are produced at these growing points.
Leaf
• A leaf consists of a leaf blade connected to the stem by a leaf stalk.
• The leaf is an organ specialized for photosynthesis.
Tissue Maps
• A tissue map (sometimes called a low-power diagram) is a drawing that records the relative positions of structures within an organ or organism.• It does not show individual cells
The distribution of tissues in the stem of the sunflower
• From the tissue map in figure 10.2, it can be seen that the stem is an organ surrounded or contained by a layer called the epidermis
• The epidermis contains:• Vascular tissue (xylem for water transport and
phloem for transport of organic solutes) • Vascular tissue is in a discrete system of veins or
vascular bundles • In the stem, the vascular bundles are arranged in
a ring, positioned towards the outside of the stem
The distribution of tissues in the leaf of the sunflower
• Figure 10.3 is a tissue map showing the distribution of tissues in a leaf
• Like the stem, the leaf is contained by a single layer of cells, the epidermis, and also contains vascular tissue in a system of vascular bundles
• The vascular bundles in leaves are often referred to as veins
• The bulk of the leaf is taken up by a tissue called mesophyll
• The cells are supported by veins arranged in a branching network.