Magazine - Frost Explained
SEARCH
POPULAR ARTICLES
NEWS ALERTS
Want to get news alerts delivered direct to your inbox?
Edit your email preferences.
RECENT COMMENTS
By Karl Danneberger in Training on 6th Dec 2006 15:00
Frost is an interesting process that occurs on clear cold nights when turfgrass plants reradiate heat (exothermic reaction). As the plant loses heat to the atmosphere the plant leaf cools. If the plant temperature is cooler than the air temperature then moisture from the atmosphere will condense on the leaf. Should the leaf temperature drop below freezing then the water freezes and frost forms. This will occur even if the air temperatures are slightly above freezing. At this time of the year it is not uncommon to have frost form even if the air temperature is in the mid to high 30's.
Frost does not form as readily on cloudy nights because the clouds reflect, or absorb and then reradiate the energy back towards the turf. Thus, the plants receive heat from this rerediation. Frost also does not form as readily under conditions where a breeze is present. Through convection the mixing air closest to the plant and the atmosphere buffers the leaf temperature drop (also promotes evaporation of the water droplets from the leaf). Areas with little slope have a greater potential for frost than sloping areas (air moves downward resulting in a mixing).
Frost will normally form early in the morning before sunrise. This makes sense because if the plants have been reradiating energy throughout the night, the leaf temperature should be the coolest prior to daybreak. Actually frost may continue to form briefly even at daybreak due to the low angles of light coming from the sun may not directly hit the leaf.
Frost itself does not cause damage, but injury does occur when traffic occurs on frosted areas. Turf damage is generally superficial. This is not to say that traffic should be allowed on frosted turf. If traffic occurs, whether it is foot or mechanical, damage caused by crushing the leaf blade will occur. Initially the symptoms will appear purplish to black in color (almost like an excessive Iron application). The damaged turf will then progress to a straw color. If no damage occurs to the crown, recovery will occur from the generation of new leaves.
Author: Karl Danneberger
Dept. of Horticulture and Crop Science
The Ohio State University
Read more articles in Training,
by Karl Danneberger
or from December 2006.
There are 4 comments on this article
9 Dec 2006 by mackay
Does water from within the plant contribute to frost at all? ie. water released through the stomata.
9 Dec 2006 by Anthony Asquith
Hi andy
As always in for a penny!
frost is predominantly 'water vapor' by 'deposition' derived from saturated air ie below freezing (frost point)
Doesn't 'supercooling' and 'ice crystals' come into it - The latter can damage cells, or so i think!
Andy as the 'stomata' needs a blue light receptor (ie zeaxant) to open the 'guard cells' obviously the 'stoma' is closed in the dark so i wouldn't say water from transpirational pull caused frost but more water vapor that 'condenses' on plants from the atmosphere does
Actualy though although 'stoma' is closed 'hydathode' structures is involved in 'guttation' and Organic compounds ie sugars etc are released - even though stoma is closed roots still take up moisture so root pressure is increased due to water potentials!
cheers
20 Dec 2006 by danneberger
First, it's great to see that actually that there are people who actually read something that I write! (ha ha). Actually, what Anthony is saying is correct. Frost occurs when the water in the air condenses on the leaf because the leaf is cooler than the air, and the water freezes. Transpiration would not be a factor because during this process transpiration would not be occurring (stomates closed, night, etc).Now, the formation of dew, which is similar to frost except it occurs above freezing temperatures does include guttation water exuded from the hydathodes. Usually, from my observation, guttation water is a much larger droplet than occurs with condensation. When frost occurs I do not think guttation water would be important but it could play a minor role.
Want to post a comment in response to this article?
Login now, or register if you are not a Pitchcare member.
Frost is an interesting process that occurs on clear cold nights when turfgrass plants reradiate heat (exothermic reaction). As the plant loses heat to the atmosphere the plant leaf cools. If the plant temperature is cooler than the air temperature then moisture from the atmosphere will condense on the leaf. Should the leaf temperature drop below freezing then the water freezes and frost forms. This will occur even if the air temperatures are slightly above freezing. At this time of the year it is not uncommon to have frost form even if the air temperature is in the mid to high 30's.
