Basics of Plant Growth

Chapter 13

Regions of Growth

• Tips of stems and roots– Terminal buds & root tips =

growth in length

• Axils of leaves– Form new stems, leaves, &

flowers

• Cambium layer in stems and roots– In dicots = growth in diameter

Concepts & Components of growth• All living material is made up of

cells or products of cells.• All cell are derived from previously

existing cells; most cells arise by cell division, but in sexual organisms they may be formed by fusion of gametes.

• A cell is the most elementary unit of life.

• Every cell is bounded by a plasma membrane.

Concepts & Components of growth cont.• All cells have strong biochemical

similarities.• Most cells are small, about .001

cm in length• The three general functions of

most cells:– Maintenance– Synthesis of cell products– Cell division

Mitosis• Simple cell division.• Daughter cells are the same

genetically as the mother cell.• There are six steps to Mitosis

– Interphase– Prophase– Metaphase– Anaphase– Telophase– Interphase

Sexual Propagation

• If the plant group will reproduce “true by seeds – with no characteristics changed – the cultivar is termed a line.

• Inbred lines – used to produce hybrid cultivars.

• Hybrid – the offspring of two plants/animals differing in one or more Mendelian characters.

Sexual Propagation

• Homozygous• Heterozygous• Genotype• Phenotype• DNA• Gene• Chromosome

• Diploid• Haploid• Recessive• Dominant• Mitosis• Meiosis

A = Adenine, T = Thymine, G = Guanine, C = Cytosine

Meiosis

• This will be covered in chapter 15

Basic Genetics

• Gene• Chromosomes• DNA• Double helix bond

– DNA Bases• Adenine (A)• Thymine (T)• Cytosine (C)• Guanine (G)

How it works• Since all living organisms are

composed of largely proteins which are made up of long chains on amino acids.

• There are 20 different kinds of amino acids found in proteins.

• Instructions from genes are transmitted indirectly by ribonucleic acid (mRNA)

• mRNA moves from the nucleus into the cytoplasm

• tRNA serves as a template for protein synthesis which will translate the codons.

Plant Hormones and Regulators• Increase profits.• Preventing lodging in cereals.• Preventing preharvest drop.• Synchronizing maturity to

facilitate mechanical harvest.• Hastening maturity to decrease

turnover time.• Reduce labor requirements.

Plant Growth Hormones

• Auxins- – 1st group of plant hormones to be

discovered, mid 1930’s– Adventitious root initiation– Weed control (2-4D)– Inhibition of stem sprouting– Tissue culture

Gibberellins-

• Increasing fruit size of seedless grapes

• Stimulating seed germination • Seedling growth• Promoting male flowers in

cucumbers• Overcoming the cold

requirement for some plants

Cytokinins-

No important agriculture use at this time.

DNA & RNA

Ethylene

• Fruit ripening• Flower initiation• Changing sex expression

(female flowers in cucumbers & pumpkins)

• Degreening oranges, lemons grapefruit

• Harvest aids

Inhibitors

• Abscisic Acid• Synthetic

• Used to regulate plant growth

Growth inputs & quality

• Timing• Amounts

Measuring plant growth, How?• Fresh weight• Dry weight• Volume• Length• Height• Surface area