1. Chapter 5b: Impact of light, cultivar, and postharvest on nutritional value of plants
Julian Verdonk
Horticulture and Product Physiology, WUR

2. Presentation structure
5.5 Light
5.6 Cultivar
5.7 Postharvest

3. 5.5 – Light quality and quantity
Intensity
Light intensity and amount
Increase in photosynthesis and carbohydrates
Damage to PSII and photo inhibition. Excessive energy cannot be channelled
Surplus of energy - adaptation and defence
Elevating concentration of phytonutrients, i.e. carotenoids, tocopherols, vitamin C, anthocyanins
Increase of ROS quenching
Increase of leaf nitrate levels
Effects on quality
Increased levels of antioxidants and phenolics can lead to increased shelf life and other quality improvements

4. 5.5 – Light quality and quantity
Spectrum
Four main photoreceptors
Phytochromes
Cryptochromes
UV-A receptors
UV-B receptors
Changes in light spectra can initiate biochemical response
Addition of colour = Reduction of other colour
Addition can lead to increased light intensity
Examine if change is due to addition, or to increased intensity
Correct for light intensity: change in light ratio
Responses are genotype dependent

5. 5.5 – Light quality and quantity
Spectrum
Some examples, very circumstantial, literature is very divided
Blue light -> more B carotene in leafy greens, broccoli
Red light -> more lutein in leafy greens, broccoli
Far Red -> reduced carotenoids in lettuce
Changes in ratio blue:red can be used to manipulate phenolic content
Green light -> reduces anthocyanin in Arabidopsis
Blue light -> increases anthocyanin in lettuce
Green and Blue light -> increase vitamin C, E, in lettuce
Etc...
Possible applications of light treatments to increase phytonutrients are currently in the experimental phase

6. 5.6 Cultivar choice Genotype and plant mineral content
Genotype and phytonutrient concentration
Grafting

7. 5.7 Postharvest Living plant products and quality
Preharvest and postharvest quality

8. Quality of living plant products is determined by physiological processes and metabolic content
Plant products are alive:
Physiological processes
Respiration
Transpiration
Development, i.e. ripening senescence
Metabolic processes
Pigment, aroma, flavour
Phytonutrients

9. Quality at harvest is determined by genotype and preharvest Shelf life is dependent on postharvest conditions
Physiological processes are determined by genotype and preharvest conditions
Low temperatures in the chain slow down these processes
Risk of Chilling injury in products with tropical origin: Tomato, Mango, Avocado, Banana

10. Quality at harvest is determined by genotype and preharvest Shelf life is dependent on postharvest conditions
Atmospheric conditions can be used to reduce respiration. Low O2 high CO2
Controlled atmosphere (CA)
Modified Atmospheric Packaging (MAP)
Long storage option possible
Apples: 6-12 months
Bagged cut lettuce: 1 weeks

11. Quality at harvest is determined by genotype and preharvest Shelf life is dependent on postharvest conditions
Light: chain is often dark, practicality
Light cannot reach full package
Darkness can lead to yellowing of green tissues
Most coloured fruit, no consequences
Addition of light to postharvest chain has positive effect: longer shelf life (slide #3)

12. Quality at harvest is determined by genotype and preharvest Shelf life is dependent on postharvest conditions
Deterioration: end of shelf life
Determined by combination of:
Physiological processes
(same as slide #8)
Mechanical damage
Pathological deterioration
Senescence: last developmental stage
Product specific:
Tomato -> softening
Lettuce -> Browning
Banana -> brown/black discoloration

13. Questions...