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Introduction to Plant Structure and Growth. IB Topic 9.1. Starting Points. Green plants are autotrophic Green plants show wide diversity: mosses (bryophytes), ferns (filicinophytes), conifers (coniferophytes), and flowering (angiosperms) Photosynthesis
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Introduction to Plant Structure and Growth IB Topic 9.1
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.
Root • The root anchors the plant • And is the site of absorption of water and ions from the soil.
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.