Plant Science 2.pdf - Plant Science Exam 2 Lecture 9 Plant tissues and Organs Plant Structure Plants began living on land 420 million years ago

Plant Science 2.pdf - Plant Science Exam 2 Lecture 9 Plant...

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Plant Science Exam 2 Lecture 9: Plant tissues and Organs Plant Structure Plants began living on land 420 million years ago. Challenges of terrestrial life led to evolution of distinct, specialized tissues and organs. All flowering plants have leaves, stems, and roots. These parts can be modified and may not be easily recognizable. No species exists for which roots, stems, or leaves have been completely lost evolutionarily. Organs – roots, stems, flowers, fruits Plants: Herbaceous or Woody Herbaceous - Do not develop persistent woody parts of the plant Woody – Develop woody tissue – trees and shrubs Annuals: Herbaceous plants that grow, reproduce and die in 1 year or season Biennials: Herbaceous plants that 2 years to complete their life cycle Perennials: Woody or Herbaceous. Live for more than 2 years. Cells and Tissues of Plants: Plant cells are organized into tissues Tissue: Group of cells that form a structural and functional unit. Ground tissue system: All tissue of the plant body other than the vascular tissues and the dermal tissue Various functions – storage, photosynthesis and plant support. Vascular tissue system: The tissue system that conducts materials through the plant body Extends throughout the plant body and can also function in supporting the plant Dermal tissue system: The tissue system that provides an outer covering for the plant body The Ground Tissue System: Composed of three simple tissues Parenchyma Collenchyma Sclerenchyma The cell wall of each tissue distinguishes them Cell wall is the structural support that surrounds each plant cell. Primary cell wall: Expands with cell as it grows Secondary cell wall: After cell stops growing cell wall is secreted inside the primary cell wall between the primary cell wall and cell membrane Parenchyma cells Have thin primary cell walls Found throughout the plant body and is the common type of cells and tissue. Active metabolically Most remain alive after they mature. Functions: Photosynthesis: Chloroplasts Storage: Starch grains, oil droplets, salts, water Secretion: Nectar, hormones, enzymes Differentiate: Less specialized cell becomes a more specialized cell type. 1
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Collenchyma cells Collenchyma cells have a thin primary wall that becomes thickened in other areas. This allows plasticity Not uniformly distributed. Found as long strands near stem surfaces and along leaf vein Celery – “strings” Sclerenchyma cells Composed of cells with rigid cell walls Both primary and secondary cell walls Secondary cell wall makes cells hard and strong – thickened cells Provide structural support Two type of sclerenchyma cells Sclereids Short cells. Common in shells of nuts and stones of fruits Fibers Long tapered cells found in groups Abundant in wood, bark and leaf veins Vascular tissue system:
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  • Spring '18
  • Nrupali Patel
  • cells, phloem, Xylem, Plant anatomy

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