Plant physiology

Lecture 2/23/09

Modification of Juvenility

• What are the 3 ways juvenility can be modified?1. Grafting/Budding

2. Pruning

3. Chemical Trt. (GA)

Senescence • What exactly does senescence start with?

1. reproduction

• What are physiological changes that in plant during senescence?

1. Loss of leaves2. Color changes3. Reduction of synthetic activity4. increase in permeability of cell membranes

Senescence Cont’d

• Termination of growth=start of senescence– Annuals- entire plant dies– Perennials- above ground parts– Biennials- entire plant dies – Deciduos-only leaves– Evergreens- shed leaves throughout year

Senescence con’t• What occurs in

animals during senescence?

1.Decline hormone production

2.Decline in enzymes (activity)

3.Decline in metabolism

4.Loss of vitality

• What occurs in plant during senescence?

1. Destructive changes (morphology)

2. Pigmentation

3. Shedding of organs (leaves)

4. Reduce foliage production

5. Reproduction decreases

6. Decrease flowering, fruiting

7. Decrease in growth rate

• What are environmental factors of senescence

1. Heat increase senescence (enzymes)

2. Darkness- degradation chlorophyll (light, Pn)

• How can senescence be modified?1. Removing flowers and fruits

2. Preventing factor that suppress growtha. Water stress

b. temp increase

c. Nutrients

3. Aging of clones.

Plant physiology

Lecture 2/25/09

Senescence

• What are theories of senescence?1. Reproduction activity (fruit filling depletes

nut; starvation foral removal

2. Growth retardants = polaris (hasting of senesence)

3. Loss of membrane integrity

4. Degradation of photosynthesis; CHO

Reproductive development

• Flowering1. Internal signal, 2. environmental

• Determinate- growing tips flower

• Indeterminate- some tips flower, others grow vegetation

• What are the various phenotypic impact of flowering?

1. leaf area

- increase photosynthesis, and increase CHO

2. nutrients- CHO (carbs, flowering needs more), N

3. Florigen- evidence of formation in leaves translocated to tips = flower induction

• What are the 3 commencement of flowering aspects?

1. Flower bud induction– Internal physiological change in individual growing

points that precedes any morphological change

2. Floral initiation: visible

3. Differentiation of flower structure leading (Anthesis)

What are the factors affecting flowering?

• 1. Nutrients- (internal) standard value: required amount of nutrient associated with optimal yield

• 2. Photoperiodism- phytochromes (Pr 680, Pfr 750 R:FR)

• Temperature- vernalization, chilling hrs (600-800), temp can modify response to day length

• e.x. poinsetta, xmas (red) flower at 18 C (short day plant)• At 12 C = long day plants at 21 C = no flowering

• Growth regulator- Gibberellins

Plant physiology

Lecture 3/9/09

Fruit & seed development

• Fruit- mature ovule- seed

• Ripened ovary = fruit

• Ripening- Correlated with seed maturation– As seed matures pericarp becomes soft &

enlarged – Sugar accumulates & bitter/sour substances

are reduced

Types of fruits

• Berry- e.x. tomatoes, grapes– Entire ovary wall becomes fleshy

• Aggregate/Drupe- series of ripened ovaries inserted in afleshy receptacle– e.x. strawberries

Types of fruits Con’t

• Drupe- Inner part of ovary wall becomes stony. e.x. cherry, plum, peach

• Pome- floral tube (fuse bases of calyx, corolla) e.x. apples & pears– Stamen fuse together at the base envelops &

fuses with ovary becomes fleshy and tasty

Classification of fruits

• 1. Fleshy

• 2. Dry• Dehiscent- opens• Indehisent- not open

• Simple fruits- develop from 1 pistil

• Aggregate/multiple develop ovaries each from a separate flower.

Classification of fruits con’t• Simple fruit:

1. Berry2. Drupe:

-exocarp- epidermis-middle layer- mesocarp-endocarp- stony

3. Pome

– Dry fruits a. indehiscent- 1. achenes (1seeded fruits)b. grain/caryopsisc. nut pericarp becomes hardened throughout

• Accumulation of compounds:– Provides essential energy substrates

(survival)– Provides food for humans

• Maturation/physiological– Involves moisture relationship– Rapid embryo enlargement equals increase

water content

• What are advantages of producing heavier seeds?

1. Better germination

2. provides more vigorous seedlings

• Production of genetically pure seeds

1. self pollination

2. cross pollination

Production of genetically pure seeds

Con’t

• Dioecy- flowers borne on separte plants

• Monoecy- flowers borne on parts of same plants

• Dichogamy- pollen shed at different time pistil is receptive

Plant Phys

Lecture 3/11/09