This Is Justin's IB biology hl2 blog.
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Lesson 38, Dicotyledonous Plant Structures/ Unit 7, Plant Science
1. Outline the wide diversity in the plant kingdom as exemplified by the structural differences between bryophytes, filicinophites, coniferophytes, and angiospermophytes.
No roots, vascular system, or cuticle.
Rhizoids similar to root hairs.
Mosses with simple leaf-like structures.
Liverworts have flattened shape called a thallus.
Filicinophytes (ferns):
Roots, leaves in fronds, and vascular system.
Cuticle on leaves.
Can form small trees but not woody.
Coniferophytes (conifers):
Shrubs to very large trees.
Advanced vascular system.
Woody stems and roots.
Angiospermophytes (flowering plants):
Highly variable in structure-tiny herbaceous to large trees
Roots, stems and leaves.
Advanced vascular system.
Can form woody tissue.
2. Draw a diagram to show the external parts of a named dicotyledonous plant including root, stem, leaf, axillary and terminal buds.
Atropa Bella-donna
[to be scanned]
3. Draw a plant diagram to show the distribution of tissues in the stem, root, and leaf of a generalized dicotyledonous plant.
Stem
Root
Leaf
4. Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues.
Tissues of the Leaf and their functions
- Palisade mesophyll: Densely packed cylindrical cells with many chloroplasts. This is the main photosynthetic tissue. It is near the upper part of the leaf.
- Upper epidermis - continuous layer of cells covered by thick waxy cuticle. Prevents water loss.
- Xylem: Pore that brings water to replace losses due to transpiration
- Phloem: Pore that transports photosynthesis products from leaf.
- Guard Cells: pair of cells open and close the stroma. Controls transpiration.
- Stoma: pore that allows CO2 out and 02 in.
- Spongy mesophyll: loosely packed round cells with few chloroplasts. Main area where gas exchange occurs.
5. Outline four adaptations of xerophytes.
- Spines instead of leaves to reduce transpiration.
- Thick stems containing water storage tissues
- Vertical stems to absorb sunlight early and late in the day, but not at midday when the light is most intense.
- Very wide sperad network of shallow roots to absorb water after it rains.
6. Outline two structural adaptations of hydrophytes.
- Air spaces in the leaf to provide buoyancy.
- Stomata in the upper epidermis of the leaf, which is in contact with the air, but not in the lower epidermis.
- Waxy cuticle on the upper surface of the leaf but not on the lower surface, which is in contact with the water.
- Small amounts of xylems in stems and leaves.
