Leaf Anatomy and Pigments
This primary pigment absorbs light in the red and blue wavelengths while reflecting green.
What is Chlorophyll a?
In the GDD formula, this represents the minimum temperature below which a plant stops growing.
What is the base temperature?
This term (Day Temp minus Night Temp) is used to manipulate the height of greenhouse crops.
What is DIF?
This "ridge and furrow" design is energy-efficient because multiple units share internal walls.
What is a gutter-connected greenhouse?
This is the specific range of light wavelengths (400–700 nm) used by plants for growth.
What is PAR (Photosynthetically Active Radiation)?
These accessory pigments (often orange or yellow) protect the leaf from damage caused by high-intensity light.
What are carotenoids?
To find the daily average temperature for a GDD calculation, you add these two daily numbers and divide by two.
What are the Maximum and Minimum temperatures?
This condition occurs when a plant is grown in low light, resulting in pale, stretched stems.
What is etiolation?
This is the most efficient greenhouse orientation for capturing winter sunlight in northern climates.
What is East-West?
At this point, the rate of photosynthesis is exactly equal to the rate of respiration.
What is the Light Compensation Point?
This is the specific internal leaf layer where the majority of photosynthesis occurs.
What is the palisade mesophyll?
Growers use GDD accumulation to accurately predict this specific event for crops or pests.
What is the harvest date (or emergence)?
This process uses cold temperatures to "switch on" the flowering process in certain plants.
What is vernalization?
This property describes a material's ability to resist heat loss; a higher value means better insulation.
What is the R-value?
Adding this specific gas to a greenhouse can help plants utilize higher levels of light.
What is Carbon Dioxide (CO2)?
These microscopic pores on the underside of a leaf regulate gas exchange and water loss.
What are stomata?
If a crop has a base of 50°F and the daily average is 75°F, this many GDDs were earned that day.
What is 25 GDD?
If a plant experiences a "negative DIF," its height will likely do this.
What is decrease (or stay compact)?
This type of cooling uses fans to pull air through a wall of wet cellulose material.
What is an evaporative (fan and pad) system?
This is the term for a plant's response to the relative length of day and night.
What is photoperiodism?
This blue-green pigment acts as a "light switch" to tell the plant when it is day or night.
What is phytochrome?
This is the term for the total amount of GDDs a specific plant variety needs to reach maturity.
What is the Heat Unit requirement?
This specific temperature point is where a plant's chemical processes begin to break down due to excessive heat.
What is the maximum threshold temperature?
To get an accurate reading, greenhouse temperature sensors must be placed at this specific height.
What is the plant canopy level?
This is the stage where increasing light intensity no longer increases the rate of photosynthesis.
What is the Light Saturation Point?