Wheat Yield as Affected by Length of Exposure to Waterlogging During Stem Elongation

Waterlogging, if occurring within the stem elongation period (SE), is particularly critical for yield determination. We quantified for the first time the effect of waterlogging duration during SE on yield and studied whether the effects were only direct on resource capture or whether there were feed-forward effects as well. We grew wheat (cv. Soissons) outdoors in long tubes (1.25m deep) forming a normal canopy and imposed different treatments in SE to finish simultaneously around anthesis (0, 4, 8, 12, 16, 20 and 24days) plus two complementary treatments (8 and 16days) starting 10 days after the onset of SE. Yield was reduced linearly with the duration of waterlogging c.2% d(waterlogging)(-1). Treatments mainly affected pre-anthesis spike growth reducing the number of fertile florets and grains, not affecting fruiting efficiency. The magnitude of grain number loss was inversely proportional to the hierarchy of the spikes and spikelets. Grain weight was more marginally reduced, likely through the effects on the size of the ovaries of the developing florets. This reveals a direct effect of waterlogging on the capture of resources with no major feed-forward effects. Losses were in agreement with those from other studies for particular durations of waterlogging.