Barley Treated with Ethephon: II. Tillering Pattern and its Impact on Yield

Abstract

Ethephon [(2‐chloroethyl)phosphonic acid] used for lodging protection in barley (Hordeum vulgare L.) often increases spikes m−2. The degree to which such additional spikes contribute to yield has not been reported, and neither has the source of such spikes been determined. This study was undertaken to determine the effects of ethephon on tiller emergence and survival, as well as the contribution to yield of additional spikes appearing on ethephon treated barley plants. Ethephon was applied at Zadoks growth stage (GS) 35 and/or 45 at 240 g ha−1 to ‘Argyle’ conventional height and ‘Samson’ semidwarf barley grown at 100 and 300 plants m−2 at Winnipeg, MB. Ten plants per plot were observed at intervals through the growing seasons; tillers were tagged as they emerged and their contributions to spikes per plant and grain yield were determined at harvest. The two cultivars responded similarly to ethephon application. In all 3 yr and at both plant densities, ethephon application increased shoots per plant. Application at GS 45 increased shoots per plant more than at GS 35 in 1987 when moisture was adequate, but less in 1988 when some moisture stress may have affected barley at GS 45. Late appearing shoots contributed up to 32 and 15% of spikes per plant and grain yield per plant, respectively, for both plant densities in 1987 and for the low plant density in 1989. Increased spikes per plant due to ethephon application were attributable to late tiller production and survival rather than to prevention of senescence of early formed tillers. The increase of spikes per plant by ethephon should be a positive influence on grain yield, but total yield per plant was often decreased and was never increased by ethephon because ethephon also caused reductions in kernels per spike.

Physiological Behavior of Ethephon in Five Turfgrasses

“…Ethephon is a growth regulator used to prevent lodging caused by inflorescence in barley ( Hordeum vulgare L.), corn ( Zea mays L.), wheat ( Triticum aestivum L.), and other grass crops (Dahnous et al, 1982; Gaska and Oplinger, 1988; Moes and Stobbe, 1991). In barley, Foster et al (1992) noted ethephon was translocated from leaves to spikes with subsequent release of ethylene.…”

Barley: Physiology of Yield

“…Bud growth is inhibited by auxins (Johnston and Jeffcoat 1977;Sharif and Dale 1980a,b) and inhibited or reduced by GA3 (Woodward and Marshall 1988;Ma and Smith 1992c). Anti-auxins (TIBA and ethephon), GA3 biosynthesis inhibitors (chlormequat chloride, mepiquat chloride and ancymidol), and formulations of ethephon and chlormequat or mepiquat chloride promote tillering (Koranteng and Matthews 1982;Woodward and Marshall 1989;Lauer 1991;Moes and Stobbe 1991b).Auxins and GA3 do not inhibit the growth of rapidly growing tiller buds (Sharif and Dale 1980a,b).…”

“…Ethephon increases the number of early (Foster et al1991;Moes and Stobbe 1991b;Taylor et al 1991) and late emerging tillers Lauer 1991), but the productivity of these tillers is often quite low and cultivardependent. Growth regulators that reduce stem growth in freely tillering cultivars have no effect on the development of tiller buds in uniculms (Woodward and Marshall 1989).…”

“…In addition to reducing lodging, ethephon application may affect barley yields by altering individual yield components either positively or negatively (Moes and Stobbe 1991b). Ethephon treatment increases the number of spikes m-2 in spring Moes and Stobbe 1991b;Smith 1992f, 1991b) and winter barley (Hill et al 1982).…”

“…Ethephon treatment increases the number of spikes m-2 in spring Moes and Stobbe 1991b;Smith 1992f, 1991b) and winter barley (Hill et al 1982). An increased spike number can result in improved yields even in the absence of lodging (Hill et al 1982).…”