Preharvest Factors Affecting the Quality of Perishable Horticultural Crops

Comprehensive practice flashcards covering preharvest factors, plant nutrition, irrigation terminology, cultural management, plant growth regulators, and physiological processes influencing postharvest quality.

What are preharvest factors?

Conditions and practices before harvest that influence the quality of agricultural produce.

How are perishable commodities defined?

Products that deteriorate relatively rapidly after harvest.

What is the difference between genotype and phenotype?

Genotype is the genetic constitution of an organism, while phenotype refers to the observable characteristics resulting from genotype and environmental influences.

What is a cultivar?

A cultivated plant variety selected for distinct, desirable characteristics.

What is a maturity index?

A measurable characteristic used to determine an appropriate harvest stage.

How is physiological maturity defined?

The stage when an organ has completed its natural development, although it may not yet be ready for consumption.

What is shelf life?

The period during which a product remains acceptable for its intended use under specified conditions.

What is storability?

The ability of produce to maintain acceptable quality during storage.

How is tissue firmness defined?

Resistance of produce tissue to deformation or penetration.

What are total soluble solids (TSS), and how are they commonly reported?

Soluble substances in plant juice, commonly estimated with a refractometer and reported as $^\text{o}\text{Brix}$.

What does titratable acidity (TA) measure?

The amount of acid neutralized during titration, usually expressed relative to a specified acid.

How is respiration rate defined?

The rate at which plant tissues consume oxygen and respiratory substrates to release energy.

What is transpiration?

Loss of water from plant tissues, especially through evaporation from surfaces.

What is senescence?

The regulated aging process that contributes to deterioration of plant tissues.

What is ethylene?

A gaseous plant hormone involved in ripening, senescence, abscission, and other developmental processes.

What is chilling injury?

Physiological damage caused by temperatures too low for a chilling-sensitive commodity but above its freezing point.

What is a physiological disorder?

A noninfectious abnormality resulting from physiological or environmental conditions.

How do climacteric and non-climacteric fruits differ in ripening behavior?

Climacteric fruits exhibit a characteristic rise in respiration associated with ripening, are responsive to ethylene, and can continue ripening after harvest. Non-climacteric fruits do not show a respiratory rise and develop limited additional sweetness after harvest.

Which common horticultural crops are classified as climacteric fruits?

Mango, banana, papaya, avocado, and tomato.

Which common horticultural crops are classified as non-climacteric fruits?

Pineapple, citrus, grape, and strawberry.

What is the major function of nitrogen ($\text{N}$), and what is the effect of excessive nitrogen application?

Nitrogen functions in protein synthesis, chlorophyll formation, and vegetative growth; excess may promote lush vegetative growth or delay maturity.

What are the major functions of phosphorus ($\text{P}$) in plant growth?

Energy transfer, root development, and nucleic acid synthesis.

What role does potassium ($\text{K}$) play in produce quality?

It aids in osmotic regulation, enzyme activation, and carbohydrate transport, supporting water relations and fruit development (though extra $\text{K}$ does not automatically increase sweetness).

Which nutrient deficiency is directly associated with blossom-end rot in tomato?

Calcium ($\text{Ca}$).

What is the major function of magnesium ($\text{Mg}$), and what are the symptoms of its deficiency?

It is a central component of chlorophyll; deficiency can cause interveinal chlorosis and reduce photosynthesis.

What are the typical deficiency symptoms of boron ($\text{B}$) and zinc ($\text{Zn}$)?

Boron deficiency can impair fruit set and cause defects; zinc deficiency may cause small leaves and shortened internodes.

What symptom is commonly caused by iron ($\text{Fe}$) deficiency?

Interveinal chlorosis in young leaves.

What is fertigation?

Application of soluble fertilizers through an irrigation system.

What is luxury consumption in plant nutrition?

Uptake of nutrients beyond the amount needed for maximum growth or yield, without necessarily increasing productivity.

What is nutrient antagonism?

A condition in which one nutrient interferes with the uptake or utilization of another.

How does waterlogging affect plant root systems?

It limits oxygen availability around the roots, causing root oxygen deficiency.

What is field capacity?

The soil water content remaining after excess gravitational water has drained.

What is permanent wilting point?

The soil water content at which a plant cannot recover turgidity under defined test conditions.

What is available water capacity?

Water held between field capacity and permanent wilting point.

What does evapotranspiration (ET) encompass?

The combined water loss through soil evaporation and plant transpiration.

What is vapor pressure deficit (VPD)?

The difference between actual vapor pressure and saturation vapor pressure at a given temperature.

What is deficit irrigation?

Deliberate application of less water than full crop water requirements.

What is turgor pressure?

Pressure exerted by cell contents against the cell wall.

What is fruit thinning, and why is it performed?

The removal of some developing fruits to reduce competition, which may improve fruit size, uniformity, and coloration.

What is crop load?

The number or total mass of fruits carried by a plant relative to its size or capacity.

What is field heat?

Heat retained by harvested produce from the field environment, which can accelerate deterioration if not removed appropriately.

Which phytohormone is synthesized in the shoot apex, transported via PIN proteins, and mediates apical dominance and adventitious rooting as depicted in the diagram?

Auxin.

Which plant growth regulator was applied to the dwarf pea plant on the right to promote stem elongation and overcome dwarfism?

Gibberellin (GA).

Which gaseous plant hormone triggers the progressive ripening and chlorophyll breakdown shown across the banana peel stages?

Ethylene.

In the grape ripening pathway shown, which plant hormone promotes anthocyanin biosynthesis, sugar accumulation, and chlorophyll degradation?

Abscisic acid (ABA).

What is the mode of action and commercial use of 1-Methylcyclopropene (1-MCP)?

It blocks ethylene perception and delays ripening or senescence in responsive commodities; it is commonly applied postharvest.

How does ethephon function in crop management?

It releases ethylene following application and can promote ripening, color development, or abscission in selected crops.

What is the primary function of paclobutrazol and chlormequat chloride (CCC)?

They are plant growth retardants that inhibit or interfere with gibberellin biosynthesis to reduce shoot or stem elongation.

What is thidiazuron (TDZ)?

A phenylurea compound with strong cytokinin-like activity used in plant propagation and developmental applications.

What is abscission?

The separation of an organ from a plant.

What colors are produced by anthocyanins and carotenoids respectively?

Anthocyanins produce red, purple, and blue coloration; carotenoids produce yellow, orange, and some red coloration.

What is the difference between chlorosis and necrosis?

Chlorosis is yellowing caused by reduced chlorophyll content, whereas necrosis is the death of plant cells or tissues.

What is the difference between abiotic and biotic stress?

Abiotic stress is caused by nonliving factors (such as drought, heat, salinity, or nutrient imbalance), while biotic stress is caused by living organisms (including pathogens and pests).

What is a latent infection?

An infection that remains unapparent until conditions allow symptoms or decay to develop.

What is the rhizosphere?

The soil region directly influenced by plant roots and associated microorganisms.

What is the harvest index?

The ratio of harvested economic yield to total biological yield on a consistent mass basis.

What is parthenocarpy?

Fruit development without fertilization.