Tutorial 4 : The colours of light

Question 1

blue light

Answer 1

enhances the growth of the stems
too much blue light can have a bad effect on plant and reduce mass in the leaf

Question 2

red light

Answer 2

enhances the growth of the leaves
more efficient at driving photosynthesis

Question 3

photosynthetically active radiation

Answer 3

plants can only use the visible light spectrum for photosynthesis

Question 4

photosynthetic photon flux density

Answer 4

the number of photons in the 400-700 nm wavelength incident per unit time on a unit surface

at a certain point, an increase in the PPFD doesn’t affect the plant anymore

Question 5

green light

Answer 5

stimulates an early rapid growth of lettuce
can penetrate deeper into the leaves increasing the entire plant’s photosynthesis

Question 6

yellow light

Answer 6

poorly absorbed by all photosynthetic pigments and has little effect on plant growth

Question 7

far-red light

Answer 7

minimally absorbed by leaves, but can drive photosynthetic activities in photosystem II and act as a photomorphogenic signal
can induce flowering

Question 8

vertical farming

Answer 8

method of growing crops in stacked layers or vertically inclined surfaces, often in a controlled indoor environment

benefits :
- higher yields per square meter
- A controlled environment reduces the need for pesticides
- reduces water usage
- year-round production
- shorter growing times
- reduced transportation costs

drawbacks :
- initial setup costs
- the need for manual pollination
- energy consumption for lighting and climate control
- technical challenges in scaling up

Question 9

hydroponics

Answer 9

growing plants without soil as a medium while providing water and nutrients. The plants are held in net pots or on chemically inert media such as clay pellets, perlite, rock wool,…

advantage :
- can reduce the evaporative loss of water and thus conserve water usage
- can be automated

disadvantage :
- disruption of the system can significantly influence the outcome of the cycle
- cost of nutrients and electricity are higher

Question 10

aeroponics

Answer 10

growing plants in an air or mist that is sprayed onto their roots several times an hour. The plants are usually supported by boards, foam sheets or other methods to suspend the plants in space

advantage :
- better aeration of the roots for the plants to grow faster

disadvantage :
- require precision sensing technology and strict dosing regime to maximise outcomes

Question 11

soil-based

Answer 11

plants are grown in soil trays where they can be moved. Soil provides plants with primary nutrients of nitrogen, phosphorous and potassium along with micronutrients such as copper, boron, zinc, manganese and molybdenum

advantage :
- soil retains moisture well and can also provide aeration
- with proper fertilisation, soil can be used repeatedly for many cycles of crops
- all types of plants can be grown on soil

disadvantage :
- soil cultivation requires a high degree of knowledge in field management, fertilisation and pest management

Question 12

aquaponics

Answer 12

growing plants and fishes together in a system. The nutrient input for this system is by feeding fishes and converting the waste into nutrients for the plants. This rely on microbes and proper functioning microbes are the key in an efficient conversion to nutrients for the plants

advantage :
- auto-sustaining, low maintenance if done properly

disadvantage :
- the start-up phase for an aquaponics system is much longer for the microbial population to grow up and stabilise
- requires a wide knowledge base in hydroponics, aquaculture and mainatance of microbes and nutrient levels