Roots, Stems, and Leaves
• The three main plant organs are roots, stems, and leaves.
• These organs are made up of three main kinds of tissues:– dermal tissue– vascular tissue– ground tissue.
Plant Tissues
• Dermal tissue –– the “skin” of a
plant. – protects the plant
and prevents water loss.
Plant Tissues cont.• Vascular tissue
– moves water and nutrients throughout the plant. • Xylem tissue
– moves water. – made up of
tracheids and vessel elements.
• Phloem tissue– moves sugars. – consists of sieve
tube elements and companion cells.
Plant Tissues cont.
• Ground tissue- – all the cells that lie between dermal and vascular tissues.– made up mostly of parenchyma cells.
• Parenchyma cells have thin cell walls and function in photosynthesis and storage.
– Collenchyma and sclerenchyma• These cells have thick cell walls that help support the plant.
Plant Tissues cont.
• Meristematic tissue- – responsible for plant
growth. – Produces new cells by
mitosis. – Develop specialized
structures and functions when mature in a process called differentiation
– found at the tips of stems and roots.
Roots• 2 types of roots-
– Taproot : One big primary root + small secondary roots– Fibrous root: Primary and secondary roots = same size
• Functions: – anchor a plant in the ground. – absorb water and dissolve nutrients from the soil.
• Root pressure forces water upward through the xylem toward the stem.
Stems
• Functions:– They produce leaves, branches, and flowers. – They hold leaves up to the sunlight. – They also carry water and nutrients between roots and leaves.
• Arrangement of tissues – Monocots: vascular bundles are scattered – Dicots : vascular bundles are arranged in a ring.
• These vascular bundles contain xylem and phloem tissue.
• Growth:– Primary : grows longer– Secondary: grows wider
Leaves• main organs of
photosynthesis. – make food (sugars) – made up of a
specialized ground tissue called mesophyll cells.
• Mesophyll : many chloroplasts responsible for photosynthesis
• veins : Xylem and phloem tissues
• Stomata: small openings – prevent water loss.
Transport in Plants• Capillary action:
– Cohesion- forces between water and water molecules
– Adhesion – forces between water and other molecules
• Transpiration pull – water moves from areas
where there is plenty of water to areas where there is little water.
• Pressure-flow hypothesis– explains how phloem
transport happens• sugars move from areas
of high concentration to areas of low concentration.
D
C
BA
Which part is responsible for photosynthesis?
If a plant becomes too dry, are the stomata in the leaves more likely to be open or closed?
• Which tissue is found in the center of a plant stem?– A. dermal tissue– B. vascular tissue – C. ground tissue
• Which of the three kinds of ground tissue serve mainly for storage? – A.parenchyma – B. collenchyma – C. sclerenchyma
• Cells that can differentiate into many plant tissues are found in A. the vascular cylinder.
B. dermal tissue.
C.meristematic tissue.
• Photosynthetic tissues in a leaf include the– A.phloem.– B.vein.– C.palisade mesophyll.
• A process in which water is lost through the leaves of a plant is called– A.transpiration.– B.photosynthesis.– C.glycolysis.
