Lecture 5

• The vascular cambium and cork cambium are lateral meristems
• Lateral meristems allow for secondary growth
• Lateral meristems are only found in conifers and woody eudicots
• Lateral meristems make wood and bark
• Secondary growth produces wood and bark
• Secondary growth occurs in conifers and woody eudicots
• Primary growth occurs in all vascular plants
• The vascular cambium is a meristem
• The vascular cambium produces secondary xylem to the  inside, which makes wood
• The vascular cambium produces secondary phloem to the outside
• The vascular cambium produces more vascular cambium to increase in circumference
• The vascular cambium produces rays
• Rays are a parenchyma that provide lateral support
• Fusiform initials make tracheids and vessel elements in the xylem
• Fusiform initials make sieve elements in the phloem
• Ray initials make rays in the xylem and phloem
• Wood is a secondary xylem
• Lignin is in the secondary walls of tracheids and vessel elements, they make wood woody
• Heartwood is the darker wood at the center, it is older and not as active
• Sapwood is the lighter wood on the outside, it is younger and it carries more water
• Growth rings appear after each year of growth because the cells made in early spring are large and throughout the year they decrease in size
• Growth rings mark each year that the plant has been alive
• The cork cambium is also known as the phellogen
• The cork cambium is a new lateral meristem
• The cork cambium arises from cylinder and cortex cells outside the vascular cambium and secondary phloem
• The cork cambium produces the periderm
• The periderm is 3 layers: the phelloderm, the cork cambium itself, and cork
• The phelloderm is produced to the inside of the cork cambium
• The phelloderm is a thin layer of living parenchymal cells present in some woody species
• Cork is produced to the outside of the cork cambium
• Cork is a layer of suberized dead cells that protects woody plants
• There is no more epidermis in mature woody plants
• Bark is all tissues outside the vascular cambium, this includes the secondary phloem and the periderm
• All fluid movement in plants follows the second Law of Thermodynamics
• The most equitable distribution of energy corresponds to maximum entropy
• Osmosis, diffusion and fluid movement because of differences in hydrostatic pressure all follow the second Law of Thermodynamics
• There is a constant exchange of fluids and gases in plants
• The cytoplasm is all the material inside the cell membrane
• There are 3 cell compartments in a plant cell
• The cytosol is the part of the cytoplasm excluding the organelles