Plant Physiol, January 2001, Vol. 125, pp. 227-240
Freezing of Barley Studied by Infrared Video
Thermography1
Roger S.
Pearce* and
Michael P.
Fuller
Department of Biological and Nutritional Sciences, The University
of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, United Kingdom
(R.S.P.); and Department of Agriculture and Food Studies, Seale-Hayne
Faculty, University of Plymouth, Newton Abbot, Devon TQ12 6NQ, United
Kingdom (M.P.F.)
Freezing of barley (Hordeum vulgare), Hordeum
murinum, and Holcus lanatus was studied using
infrared video thermography. In the field, ice could enter H.
lanatus leaves through hydathodes. In laboratory tests with
barley, initially 0.4% of the leaf water froze, spreading in alternate
strips of high and low freezing intensity longitudinally at 1 to 4 cm
s
1, and simultaneously spreading laterally at 0.3 cm
s1. Similar results were obtained in the field with
H. lanatus. A distinct second, more intense, freezing
event spread slowly from the margins of the leaves toward the midrib.
Organs of uprooted barley tested in the laboratory froze in this order:
nucleated leaf, roots, older leaves, younger leaves, and secondary
tillers. When ice spread from one leaf to the rest of the plant the
crown delayed spread to the roots and other leaves. There was a longer delay above than below 
2°C, helping to protect the crown from freezing during mild frosts. Initial spread of freezing was not damaging. However, the initial spread is a prerequisite for the second
freezing event, which can cause damage. The route of the initial spread
of ice may be extracellular, drawing water from more gel-like parts of
the cell wall.
1
This work was supported by the Biotechnology and
Biological Science Research Council (grant no. 321/JEI09421).
*
Corresponding author; e-mail R.S.Pearce{at}ncl.ac.uk; fax
44-191-222-8684.
© 2001 American Society of Plant Physiologists
