1. CS313 Basics of Plant Growth
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Crop Science Library

2. Ways to measure plant growth:
Fresh weight
Dry weight
Volume
Length
Height
Surface area

3. What makes a plant grow the way it does?
Form and shape change with a plant’s overall size due to genetic factors.
Plant growth occurs because
The number of plant cells increase through division (new cells) AND
The size of the cells increase as they become differentiated into specialized tissues and organs.
Heredity and environment interact to determine growth and growth patterns.

4. Where new cells form: Tips of stems and roots – increasing length
Axils of leaves – form new stems, leaves and flowers
Cambium layer in stems and roots – increasing diameter of stems, roots and tree trunks

5. “Meristem” The term applied to a region of plant growth
These cells actively divide.
They also mature, increase in size and change into specialized tissue.

6. “Differentiation”
Changes in cells to form specialized parts of the plant.
Example: In a young root, differentiation results in the formation of different types of tissue for conduction of water and food, storage of food, protection and the uptake of water and minerals.

7. Three general cell functions:
Maintenance
Synthesis of cell products
Cell division
All these functions require energy.
ATP (adenosine triphosphate) is the universal energy transfer molecule.

8. “Morphogenesis”
Plants begin as a single cell, but by repeated cell growth and mitosis, or division, eventually contains billions of cells.
This process of development is called morphogenesis.
Morphogenesis involves not only cell growth but differentiation into specialized types of cells.
This differentiation is controlled by the genes.
Each cell manufactures the proteins and structures necessary for its function.

9. Genes are the basic unit of inheritance.
Genes are carried on chromosomes in the cell nucleus.
Genes contain the blueprint or code for how the plant will look and interact with its environment.
The number of chromosomes varies from species to species, but is consistent within a species.
Chromosomes come in pairs in normal cells.
Genes are made of DNA (deoxyribonucleic acid)

10. The “genome” is the master blueprint:
The complete set of instructions for the organism.
Found in every nucleus of cells, the genome consists of tightly coiled threads of DNA and associated protein molecules, organized into structures called chromosomes.

11. What about DNA?
Two strands that wrap around each other to resemble a twisted ladder whose sides, made of sugar and phosphate molecules
Connected by rungs of nitrogen-containing chemicals called bases.
Each strand is a linear arrangement of repeating similar units called nucleotides, which are each composed of one sugar, one phosphate and a nitrogenous base.

12. The 4 bases of DNA: Adenine (A) Thymine (T) Cytosine (C) Guanine (G)
The order of the bases is called the DNA sequence.
Each time a cell divides into two daughter cells, its full genome is duplicated.

13. Control of growth:
Heredity – the general species characteristics and limits on size and rate of growth
Hormones
Nutrition
Environment
© 2005 Nancy Crombie.

14. The role of plant hormones:
Classes include: auxins, cytokinins, gibberellins, abscisic acid and ethylene.
Cytokinins are especially important in cell division.
Elongation is promoted by auxins and gibberellins.
Several hormones interact for cell and organ differentiation.
The initiation of roots by auxins and of buds by cytokinins depends on the presence of opposing hormones in the proper amounts.
Hormones regulate other growth-related activities including seed germination, flower and fruit development, and leaf enlargement.

15. Environment plays a part …
Temperature – warm temperatures favor more growth; cold is required for some seeds to germinate, some buds to begin growing, and some plants to flower.
Light regulates flowering, leaf expansion, stem elongation, movement of leaves and seed germination.
© 2005 Nancy Crombie.

16. Plant growth regulators (PGR):
Organic compounds, other than nutrients, that modify plant physiological processes
PGRs act inside plant cells to stimulate or inhibit specific enzymes or enzyme systems and help regulate plant metabolism.
Used to modify crop growth rate and growth pattern
May occur naturally or be synthetically produced

17. Some examples of PGRs:
Auxins act to stimulate or inhibit growth, form roots on cuttings, etc.
Gibberellins control cell elongation and division in plant shoots.
Cytokinins act in cell division, cell enlargement, senescence and the transport of amino acids in plants.
These three are often used in combination for specific effects.
Inhibitors prevent enzymes from breaking down.
Ethylene is often used with auxins to regulate metabolism.

18.
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