Exercise 7: Plant Cells and Tissues

• Scientific name for corn?

  Zea mays
• Histology

  • study of microscopic structures of tissues
• Meristems

  • embryonic tissue regions that are actively and indefinitely producing new cells
• All cell types in plants that make up tissues differentiated from meristems
• Meristems

  • has thin cells walls, small amount of endoplasmic reticulum, undifferentiated proplastids, dispersed small vacuoles
  • large nuclei
• 2 classifications of meristems based on location:

  1. apical meristem
  2. lateral meristem
• Apical meristem

  • type of meristem that produces cells at the tips of main and lateral shoots and of the roots
  • vertical growth
• Lateral meristem

  • type of meristem that ads inward or outward of plant body
  • horizontal growth
• 3 BASIC cell types in plant tissues based on morphology

  • parenchyma
  • collenchyma
  • sclerenchyma
• Parenchyma

  • have thin and uniformly thick primary cell walls
• Collenchyma

  • have thick and uneven primary cell walls made of pectin
• Sclerenchyma

  • has thick secondary cells walls made up of lignin
• Plant body consists 3 tissue systems (running continuously from root to shoot)

  • dermal tissue system
  • ground tissue system
  • vascular tissue system
• Dermal tissue system

  • lines external surfaces of organs
• Ground tissue system

  • functions in mechanical support, metabolism, storage
• Vascular tissue system

  • translocates water, photosynthetic products, and other materials throughout the plant body
• Parenchyma

  • most common in ground tissue
• Specialized parenchyma

  • Aerenchyma
  • Chlorenchyma
  • Secretory Parenchyma
  • Storage parenchyma
• Aerenchyma

  • irregularly shaped cells that bound large airspaces
• What specimen is used to observe aerenchyma?

  Leaf stalks of canna

  
• Chlorenchyma

  • possess chloroplasts
  • function in photosynthesis
• Secretory Parenchyma

  • line canals and possess large vesicles that contain various substances
• chlorenchyma

  • specimen: section of leaves of Hydrilla

  
• aerenchyma

  specimen: cross section of leaf stalks of canna sp.

  
• secretory parenchyma

  • line canals and has large vesicles (containing various substances)
  • specimen: cross section of pinus sp.
• secretory parenchyma

  • lining structures called resin ducts
• secretory parenchyma

  • can be found in grandular trichomes
• Storage parenchyma

  • has leucoplasts filled with starch, proteins, or oil
• Storage parenchyma

  • specimen: potato tuber stained w/ IKI
• Are leucoplasts colorless?

  Yes
• Collenchyma

  • provides flexible structural support, especially in still growing younger regions
• Collenchyma

  • specimen: cross section of leaf stalks of Coleus
• Collenchyma

  • thickened walls of several cells may meet and appear brighter in the section, whereas protoplasts are more dimly lit
• Where to find collenchyma?

  periphery of cross sections, below epidermis
• Collenchyma

  
• Sclerenchyma

  • present in ground and vascular tissues
• Parts of sclerenchyma that function in structural support:

  1. Fibers
  2. Sclereids
• Fibers

  • part of Sclerenchyma
  • elongated and flexible
• What and how to prepare specimen in observing fibers?

  • cotton fibers stained with 18% alcoholic phloroglucinol-sulfuric acid
• Sclereids

  • part of Sclerenchyma
  • short and inflexible