Horticultural Crops and Branches of Horticulture

Stomata

• Stomata are adjustable pores that occur only in the lower or upper epidermis of some species
• Stomata are open during the day for CO2 absorption and closed at night when photosynthesis is shut down
• Opening and closing of stomata are controlled by changes in the shape of the 2 guard cells that surround each pore
• When water moves into the guard cells, they become turgid (swollen) and bend, producing a pore
• When water leaves, they become flaccid (limp) and collapse, closing the pore

Stomata Opening and Closing Mechanism

• Absorption of blue light by the yellow pigment in the plasma membranes of the guard cells triggers pumping out of protons (H+)
• This proton gradient drives potassium ions into the guard cells through facilitated diffusion, dragging along chloride ions to balance electrically
• These ions accumulate in the vacuoles, increasing their solute concentration, allowing water to move into the guard cells from surrounding epidermal cells by osmosis
• In the late afternoon or early evening, stomata close, but not through an exact reversal of the opening process

Classification of Crops

• Plantation crops: perennial growth, requiring primary processing before utilization (e.g. oil crops, beverage crops, spice crops, fiber crops, medicinal crops, latex or raisins)
• Agronomic crops: herbaceous plants grown in cultivated fields with more or less extensive system of culture
• Agro­nomic use classification: grouping according to the way crops are used (e.g. cereals, seed legumes, forage, roots, tubers, fiber, drugs, sugar, oil)

Horticultural Crops

• Grown under systems of intensive culture in relatively small areas
• Includes garden crops, plants, and cut flowers, cut foliage, flowering pot plants, landscape plants, foliage crops
• Branches of horticulture: pomology, olericulture, ornamental horticulture (floriculture, ornamental nurseries, landscape design)
• Main groups of horticultural crops: fruits, vegetables, ornamentals, and pineapple

CAM Plants

• Fix CO2 at night by combining 3-C compound to form a 4-C compound temporarily stored in the vacuoles of leaf cells
• During the day, CO2 is removed from the 4-C compound, and thus available for fixation into sugar by the Calvin cycle

Cellular Respiration

• A series of chemical reactions that break apart fuel molecules and transfer energy stored in the bonds of ATP
• Cells use 3 catabolic pathways: aerobic respiration, glycolysis, and citric acid cycle
• Aerobic respiration: requires O2, fuel molecules are catabolized to CO2 and water
• Glycolysis: takes place in the cytoplasm, does not require O2, and produces pyruvate

Plant Development

• Juvenile stage: almost all food reserves are used to produce roots, stalks, and leaves
• Mature stage: leaf and stalk growth ceases or slows down, and most products of photosynthesis are utilized for fruit growth
• Embryo: the rudimentary plant resulting from fertilization
• Germination: the resumption of growth of the embryo by absorption of water to deactivate growth regulators, activate hormones, release enzymes, and soften the seed coat