Plant Physiology and Growth Quiz

Study Notes

The study of the different physiological processes and functions in plants
Plant functions include capturing energy and assimilating carbon, distributing nutrients and water, growing and developing, responding to the environment, and reproducing

Growth occurs in meristems, which are tissues containing cells that divide to make new cells
During growth, cells divide, elongate, and differentiate into structures like roots and shoots
Meristems can produce new meristems called primordia

Shoots elongate or grow in height at the tips of branches
Apical meristems are located in the terminal buds at the tips of the branches
Cells at the apical meristem divide, elongate, and differentiate in distinctly visible steps:
- The bud at the tip of the branch opens
- Leaves emerge and enlarge
- The area between the leaves expands (i.e., the stem grows)
Lateral (side) buds grow in the same way, but often these are dormant and do not grow until released after activities like pruning

On the surface of the apical meristem in the bud, a new meristem is formed, known as the leaf primordium
The leaf primordium is where cells divide and grow into a leaf
A new bud primordium is formed at the base of each leaf stem, known as the axillary bud
The axillary bud has the capacity to become a branch but may lie dormant for many years

Between the wood and bark is a thin layer of dividing meristematic cells called the vascular cambium
The cambium divides, producing new wood towards the inside and bark on the outside
Two types of new growth that occur:
- Xylem: Carries water and minerals up from the roots to the leaves. Old wood is the heartwood and supports the weight of the tree
- Phloem: Carries sugars and other materials to the growth and storage locations of the tree
New layers of wood are added each year between the bark and the previous year’s wood
These are called growth or annual rings and may be used to age a tree
Annual rings vary in size and thickness depending on the season they are formed
Cells produced in the spring are larger with thinner cell walls; this is called "early" or "spring" wood
Cells produced in the summer are smaller and have a higher density and darker color; this is called "late" or "summer" wood
All woody trees have an outer bark that constantly renews itself and protects the tree from pest attacks and environmental impacts like fire and mechanical injury
The bark thickens as the tree ages and is influenced by the activity of the cork cambium

Absorption is the process where a fluid is dissolved by a liquid or solid (absorbent)

The process in which atoms, ions, or molecules from a substance adhere to a surface

Plants take up water and essential minerals through their roots
Roots have a high surface area to optimize uptake
The monocotyledon root has a fibrous, highly branching structure, which increases surface area for maximal absorption
The dicotyledon root has a main tap root, which can penetrate deep into the soil to access water and minerals, as well as lateral branches to maximize surface area
The root epidermis may have extensions called root hairs, which further increase surface area for mineral and water absorption
These root hairs have carrier proteins and ion pumps in their plasma membrane, and many mitochondria within the cytoplasm to aid active transport

Diffusion: Movement of minerals along a concentration gradient
Mass Flow: Uptake of mineral ions by means of a hydrostatic pressure gradient. Water being taken into roots via osmosis creates a negative hydrostatic pressure in the soil. Minerals form hydrogen bonds with water molecules and are dragged to the root, concentrating them for absorption
Fungal Hyphae: Absorb minerals from the soil and exchange with sugars from the plant (mutualism)