Temperature is the most manipulated environmental parameter inside nursery and indoor farms . Temperature controls the rate of flora development and thus set crop production meter . It also regulates harvest quality attribute including stem elongation and , for some crops , promotes or inhibits efflorescence . Below are some compelling reasons to deliver are the relatively low temperatures at night , but also some swap - offs that want to be considered . A low night temperature : decreases respiration . Plant respiration uses sugars ( primarily yield from photosynthesis ) as the energy source for various sustainment processes . The rate of breathing ( the pace of sugar expenditure ) broadly speaking increase with temperature . Therefore , a lower temperature decreases external respiration during the nighttime when most plants do not perform photosynthesis .
A low night temperature decreases respirationLess ventilation at dark translates into a higher concentration of sugars during the day , which can be used to support ontogeny processes such as the formation of young leave , tooth root , and bloom .
A humble night temperature head off heat time lag of floweringHeat accent hurts plant development and flowering . Research has shown that plants can tolerate heating plant stress much well during the twenty-four hours ( in the presence of light ) than at night . What constitutes heat stress , therefore , calculate on the time it occurs as well as the crop . One exercise of heat stress is the delay in the efflorescence of some greenhouse crops .
scant - twenty-four hours plants only heyday , or bloom earlier , when the night duration is farseeing than some metal money - specific duration , normally more than 12 minute . The inflorescence of some forgetful - day plants , include chrysanthemum and poinsettia , is delayed when the night temperature is mellow . What constitutes a high temperature varies somewhat by specie , but nights warm than around 74 ° F can delay the flowering of these two crops . Therefore , providing relatively cool temperatures at night can prevent flowering time lag of sensitive short - day plants .
A low night temperature lowers the greenhouse fuel billIt is estimated that around 75 to 80 % of greenhouse heating occurs at night . decrease the night temperature lessen the amount of vigor consumed for heating , even when the day temperature is increased to maintain the same average daily temperature .
The relative energy saving depend on location , fourth dimension of year , etc . , but can be especially compelling in the dusk and outflow . However , decrease the night temperature without an get-go to the 24-hour interval temperature lessen the ordinary daily temperature , which decelerate down plant development and increases craw timing . Therefore , if you lower the night temperature without increase the day temperature , you will require to add time to the crop schedule .
A depleted night temperature creates a + DIFStem elongation of many harvest increases as the deviation ( DIF ) between the day temperature is increasingly higher than the Nox temperature . For example , a 72 ° F day and 63 ° F night temperature creates a 9 ° F + DIF . Plants were grown at this + DIF will be taller at flower than plants grown with less of a day/ night temperature differential , specially compare to plant grown on a day that is cooler than the night . Thus , plants are grown at a + DIF might require higher pace of works emergence retardants , or other height - crush technique , to achieve prey heights compare with plants spring up at a lesser DIF value .
A low night temperature diminish the H2O vaporisation - air pressure deficit ( VPD)As discussed in a December 2021 article , decreasing the aura temperature lessen the H2O vapour it can book , lessen the VPD ( and increasing the comparative humidness ) . The air travel temperature must n’t decrease to the dewpoint , which is when saturation occurs . When this happens , the VPD is zero , weewee vaporization condenses into liquidness , and the leaves become pixilated . This term is lucky for the spread of pathogens admit bacterium and kingdom Fungi . Generally , maintaining a VPD of majuscule than 0.3 kPa is recommended for plant output . This translate into a comparative humidness of less than 85 % at 63 ° F and 88 % at 68 ° F.
In summary , lowering the nighttime temperature decreases works internal respiration , prevents heat delay , and decreases the amount of vigour consume for glasshouse heat from declivity through spring . However , to offset a low Nox temperature , the day temperature needs to be increase , which creates a + DIF that promotes fore elongation . Finally , look at the gist of temperature on the amount of water vaporization in the breeze to ensure the vapor - imperativeness deficit is at least 0.3 kPa ( relative humidity is less than 88 % )
write by Erik Runke , prof and floriculture Extension specialist in the department of horticulture at Michigan State University .
For more selective information : Michigan State University[email protected]www.canr.msu.edu
