1. Plant Structure, Growth, and Development
Chapter 35

2. Remember levels of organization…
Organism 
Organ Systems 
Organs 
Tissues 
Cells

3. Monocots vs. Dicots
Before we start, we will be looking at 2 different groups of angiosperms:
Monocots
Dicots

4. Plant Parts (organs/organ systems)
There are 3 main parts to plants:
Roots
Stems
Leaves

5. Root System
Vascular tissue in the center, surrounded by the endodermis
Cortex surrounds vascular cylinder (starch storage)
Outer covering is epidermis

6. Root Structure and Function
Roots aide in anchoring the plant in place
Most water absorption takes place towards tips of roots
Root tips have highest number of root hairs
Root hairs increase surface area for water absorption

7. Types of Roots Taproot – One large central root with branches
Fibrous – Mat of thin roots
Adventitious – Above ground roots

8. Stems
A stem is defined as an alternating system of nodes and internodes
Nodes – The points at which leaves are attached
Internodes – The stem segments between nodes
Between leaves and the stem, there is an axillary bud
Axillary Bud – A structure that has the potential to form a vegetative branch
The tip of every stem has a terminal bud
Terminal Bud – Embryonic tissue at the tip of the stem made of developing leaves, nodes, and internodes

9. Leaves Leaves are the main photosynthetic organs of plants
Leaves consist of a flattened blade and a stalk
Petiole – joins the leaf to the node

10. Leaf Structure
Epidermis is composed of tightly interlocked cells covered by a waxy cuticle
Stomata – Pores in epidermis flanked by guard cells that control gas exchange
Mesophyll – The are ground tissue between upper and lower epidermis
Mainly composed of photosynthetic perenchyma
Vascular tissue is arranged similarly to stem
Branches off vascular bundles are known as veins

12. Plant Tissues Plant organs are composed of 3 types of tissues: Dermal
Vascular
Ground

13. Dermal Tissue AKA – Epidermis Single layer of tightly packed cells
Roles of the Dermal Tissue:
Protection
Water retention (Cuticle)
Water absorption (Root hairs)

14. Vascular Tissue Two types of vascular tissue:
Xylem – Conveys water and dissolved minerals upwards, from roots to shoots
Phloem – Transports food made in leaves to the roots and other non-photosynthetic parts

15. Vascular Tissue: Xylem
Tracheids and vessel elements are the water conducting elements of xylem
They are elongated cells that are dead at functional maturity
When they die, the cell walls thicken leaving tubes for water to flow through
There are pits in the cell wall that aid in the transport of water
(More to come on transport in plants in the next few days)

16. Vascular Tissue: Phloem
Phloem is formed by chains of cells called sieve-tube members
They are alive when functioning
Vital in the transport of sugars and other organic compounds

17. Vascular Tissue: Ground Tissue
Divided into 2 types:
Pith – Ground tissue internal to the vascular tissue
Cortex – Ground tissue external to the vascular tissue

18. Types of Cells Parenchyma – typical plant cells
‘Non-Specialized’ cells
Photosynthesis and various other processes occur in these cells
Collenchyma – Cells that aide in the support of young plant shoots
Have thickened cell walls, but no secondary walls (they do not inhibit growth)
Sclerenchyma – Support cell shoots also
Have thickened secondary walls, prevent growth once formed and hardened
Ex – Hemp fibers, and nut shells are composed of these cells

19. Plant Growth
Apical Meristems – Embryonic tissues at the tips of roots and buds of shoot that produce lateral growth
Primary Growth – Elongation of plant (roots grow down, shoots grow up)
In roots, there is a root cap which protects the meristems
Lateral Meristems – Cylinders of dividing cells along the length of roots and shoots
Secondary Growth – Progressive thickening of the roots and shoots