Frost Injury in Wheat Ears After Ear Emergence

Abstract

The reaction of ears of wheat (Triticum aestivum L.) to frost after their emergence from the flag leaf sheath was studied for a number of cultivars under controlled conditions of radiative and convective energy exchange. Frost injury was measured in terms of the fertility of the ear, viz. number of grains set per spikelet. Despite being covered with frost crystals, the ear was unaffected by freezing temperature until a threshold level, below which there was a steep reduction in grain set, approximating 100% per 1°C. A threshold of about -4°C and T50 of -4.7°C were observed for the hardiest cultivar, Florence. Crystallization can be initiated within a supercooled floret by spread of freezing from either the peduncle or the vegetative structures of the spikelet. Neither of these pathways was critical and it was concluded that any nucleation in the rachis was sufficient to result in the patterns of injury described. A mechanism of injury was discussed, based on the proposal that nodal regions within the rachis and rachilla provided a distributed system of bamers to the spread of crystallization. These could be effective in allowing supercooled reproductive organs to remain so and avoid lethal injury.

Irrigation of Field Crops in the Boreal Region

“…On the other occasions, the spike consisted of both fertile and sterile spikelets. The occurrence of sterile spikelets did not depend on their position within the spike, whereas the higher order florets within the spikelet remained fertile in many cases www.intechopen.com (Marcellos & Single, 1984). Marcellos & Single (1984) explained this phenomenon by discontinuous extension of ice nucleation within the spike.…”

“…The occurrence of sterile spikelets did not depend on their position within the spike, whereas the higher order florets within the spikelet remained fertile in many cases www.intechopen.com (Marcellos & Single, 1984). Marcellos & Single (1984) explained this phenomenon by discontinuous extension of ice nucleation within the spike. An ice front can move from a single nucleating point on a leaf at approximately 120 cm/min, but it is delayed by nodes in the stem, rachis and spikelets (Andrews, 1987).…”

“…In the Boreal region, winter rye can sometimes be damaged by spring frost at the time of pollination, causing incomplete fertilization of florets and leading to reduced grain yield. A low temperature of -4 °C caused disruption of membrane structures in wheat spikes at the heading stage (Marcellos & Single, 1984). That resulted in destruction of entire spikes on some occasions when temperature decreased 1 °C below a cultivar-dependent threshold temperature.…”

“…The risk of late spring frosts and early autumn frosts is likely to decrease due to climate change (Olesen et al, 2011). There is still an avenue for plant breeding in improving frost tolerance at the grain filling stage in cereals since genetic variation for the trait is known to exist (Marcellos & Single, 1984), as well as at early growth stages. In dry areas, especially in a Mediterranean climate, selection of drought tolerant crop species and cultivars has been considered to be one of the most important means of alleviating agricultural problems (Ashraf et al, 1992).…”

In-field methods for rapid detection of frost damage in Australian dryland wheat during the reproductive and grain-filling phase

“…Frost can cause death of anthers and embryos (Cromey et al 1998), resulting in sterility of florets and whole spikelets (Marcellos and Single 1984;Al-Issawi et al 2013), thereby impacting yield. Visible symptoms may include bleaching of awns and anthers, which become pale yellow or white and shrivelled.…”