Tissues and Primary growth of stems
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How are flowering plants classified?
Magnoliophyta or Angiosperms
Magnoliophyta are divided into three groups, name them.
Basal angiosperms Eudicots (dicotelydon- broad leaves) Monodicots( monodicotyledon-narrow leaves)
What is the primary body?
It is the herbaceous body that is derived from shoot and root apical meristems.
What primary tissues make up the primary body?
Epidermis pith (central part of stem, starch storage, intercellular gas exchange, transport of substances from vascular bundle to outer stem) cortex (collenchyma (support), parenchyma (making food) and endodermis (storage), and others
What is the secondary body?
The secondary plant body is derived from meristems other than the apical meristems growth of secondary tissues in the vascular or cork cambia, it results in the development of wood and/or bark.
What are meristemic tissues in plants?
These are dividing tissues that help the plant grow and are restricted to three parts of the plant apical meristem (growing tips of roots and stems), Lateral meristems (cambium
What are the 3 classes that all cells are divided?
Parenchyma, Collenchyma and Sclerenchyma
What are parenchyma cells?
These are cells are thin walls and make up the soft portions of the plant. They remain metabolically active as they mature.
What are the types of parenchyma?
Chlorenchyma , Glandular cells and Transfer cells
What are chlorenchyma?
These cells are speciallised to do photosynthesis - they have thin transparent walls that allow light to enter -they contain chloroplasts for capturing sunlight
What kind of cells are pigmented cells?
Pigmented cells are parenchyma as the walls are thin enough to see the pigments.
What are glandular cells?
These are parenchyma with a lot of golgi apparatus and ER
What are Collenchyma?
These are cells that have unevenly thickened walls as it is only at the corners of the cell.
What do Collenchyma cells do?
These are cells that provide plastic strength to the cell allowing them to be flexible.
Where are collenchyma cells present?
• Under the epidermis of the plant • Supporting the vascular bundle • cortex • leaves
What are sclerenchyma?
These have cell walls that are thick with lignin.
What do sclerenchyma do for the plant?
Elasticity allows for the plant to return to their original shape when deformed. Strength provides the plant with support despite lack of turgor pressure
What are the types of Sclerenchyma?
Conducting and Mechanical
What are two types of mechanical Sclerenchyma?
Fiber and Sclereid
What are Fibers?
• Long and flexible - Mostly found in areas that need strength to support but need elasticity to bend
What are Sclereids?
• Short and cuboidal • Has strong walls that make it inflexible and brittle • Forms hard, impenetrable • small plasmodesmata remain free of secondary wall (lignin) become narrow pits
What are pit-pairs?
Pit pairs are plasmodesmata that are next to each other in the secondary wall.
What are conducting sclerenchyma?
Transports water
What are examples of conducting sclerenchyma?
Tracheary elements of the xylem (tracheids and vessel elements)