Vegetative Growth- stems

Question 1

What are five functions of stems?

Answer 1

1. Mechanical support of branches, leaves flowers, and fruit
2. Conduct water and nutrients up to leaves and metabolites from leaves to other plant parts
3. Some stems are green and capable of photosynthesis
4. Storage: includes food storage of economic value in crops e.g. potatoes
5. Crop propagation e.g. potatoes

Question 2

What is a meristem?

Answer 2

zone of cell division and enlargement

Question 3

Types of meristems

Answer 3

1. Apical: at tips of shoots and roots
2. Intercalary: between differentiated tissues
3. Lateral: expands tissues laterally increase in girth- also called cambium

Question 4

Epidermis

Answer 4

protection

Question 5

cortex and pith

Answer 5

storages

Question 6

Vascular bundles

Answer 6

xylem: conducts water and nutrients
Phloem: conducts food and metabolites
Vascular cambium: meristematic tissue between x and p; increases stem girth

Question 7

crown

Answer 7

a compact zone of nodes w/o internode elongation, usually located at base of plant

Question 8

Growth regulators

Answer 8

Giberellic acid enhances internode elongation.
Removal of apical meristem promotes tillering/ branching.
> application of auxin restores normal tillering/ branching

Question 9

Light

Answer 9

Darkness causes extreme internode elongation (etiolation)
Daylength effect
> early planting of corn results in shorter internodes (short-day response)
> Long days cause an increase in internode length

Question 10

Tiller

Answer 10

secondary stem that grows from crown of grass plant

- like a side branch in dicots

Question 11

Tillering

Answer 11

refers to development of axillary buds (shoots) of grasses

• intravaginal branching: shoot emerges within enclosing leaf sheath
• extravaginal branching: shoot breaks through the base of the leaf sheath

Question 12

Factors that affect branching/tillering

Answer 12

1. Genotype: the number of tillers is under genetic control
2. Light and plant density: under favorable conditions small grains produce max # of culms per acre regardless of seeding rate
3. photoperiod and temp: tillering of small grains is stimulated in response to short days and cool temps of fall
4. water and minerals: tillering is dependent on factors that favor rapid vegetative growth
   - good tillering (and braching) response in grasses to N and water
5. Clipping and grazing: removal of apical buds can stimulate tillering
   - will typically reduce grain yield due to loss of leaf area

Question 13

four crop management practices related to stems

Answer 13

1. plant density: branching and tillering affected by plant density
   - plant response varies with species
2. weed control: weeds with rhizomes and stolons are difficult to control by tillage
   - herbicides must be applied at proper growth stage of crop
3. Fertilization: tall cultivars more susceptible to lodging; exacerbated by high N fertilization
   - dwarf cultivars more responsive to high N
   - P promotes rooting K prootes strong stems
4. Cultivar morphology
   - grass crop cultivars differ in tillering habits
   - determinate vs. indeterminate cultivars in soybean
   - cultivars with more or less branching