Abstract
Successful stand establishment is prerequisite for optimum crop yields and can be affected by seeding depth. A field experiment
was conducted to investigate the effects of seeding depth on agronomical characteristics, structural feature of subcrown
internode (SCI), plant growth and ultimately grain yield of winter wheat. Seeds of Luyuan 502 were sown at four seeding
depths (10, 25, 40 and 55 mm). The results showed that increasing the seeding depth from 10 to 40 mm increased seedling
emergence rate, numbers of fall tillers per unit area and per plant. Seeding at 55-mm depth significantly decreased the seedling
emergence, tillering capacity, spikes per unit m2
; however, the fertile tiller percentage significantly increased compared with
shallower seeding. At 10-mm soil depth, there was no SCI produced; at 25 to 55-mm soil depth, the length of SCI increased
with increasing of depth. However, the diameter of SCI and diameter and wall thickness of SCI xylem vessel decreased.
Regarding hormonal concentration in SCI, GA3 and IAA increased with increasing seeding depth, whereas the maximum ZR
and ABA contents were observed at 40-mm soil depth. Similarly, the maximum rate of oxygen consumption was also observed
in SCI of 40-mm-sown plants. Transmission electron microscope observations showed many mitochondria in the companion
cell (CC) and many plasmodesma connecting CC and sieve element. As the seeding depth increased, values of the normalized
difference vegetative index and shoot dry matter weight decreased but interestingly, the highest grain yield was obtained in
40-mm-sown wheat, followed immediately by that at 55-mm depth. It is concluded that wheat sown at about 40-mm soil depth
may be optimal for winter wheat growth and production in northern China
