Differences in flowering responses of wheat to temperature and photoperiod

Abstract

Apex and ear development were studied in one spring wheat (Hartog) and five winter wheats (Rosella, Maris Templar, Maris Huntsman, Priboy and Krasnodar 39) subjected to vernalizing or non-vernalizing temperatures under either short or long photoperiods until ear initiation (double ridges), followed by either short or long photoperiods until ear emergence. Hartog produced ears in all treatments, and it initiated ears faster than winter varieties in all treatments. Four types of winter wheat were distinguished by their mandatory requirements for ear development. The only winter variety to reach ear emergence without vernalization was Maris Templar; short days were an effective substitute provided that long days were experienced after ear initiation. In Priboy, photoperiod was unimportant both before and after ear initiation. Maris Huntsman and Rosella required long photoperiods after initiation, whereas Krasnodar 39 required long days during vernalization. If these conditions were not met, either the shoot apexes died without producing a terminal spikelet or the ears died before emerging. Plants in all treatments which reached ear emergence proceeded normally to maturity. The suitability of the different types for particular regions is discussed. All varieties in all treatments initiated ears when the shoot apex reached a volume of about 0.13 mm3. Relative growth rates of the apex, related to thermal time, were constant during the vegetative phase; they determined the time to ear initiation and, through it, controlled the time of ear emergence. Differences between varieties in their basic vegetative period are attributed to differences in the relative growth rates of their vegetative apexes. These growth rates were much lower in winter wheats than in the spring variety, but increased sharply in them at or just before the first visible signs of initiation in those treatments which allowed normal development. Vernalization was not the cause of this accelerated growth. In winter wheats, vernalization promoted faster initiation of ears, and hence flowering, and the survival and normal development of initiated ears. It is suggested that vernalization acts by reducing the effectiveness of an inhibitor of cell division.

Variability in the Duration of Stem Elongation in Wheat Genotypes and Sensitivity to Photoperiod and Vernalization

“…At the end of the experiment, only 15 % of the unvernalized plants of ProINTA Puntal had reached anthesis, while the other plants remained vegetative until they senesced. Similar results were also found in other winter wheats (Rahman 1980, Manupeerapan et al. 1992, Slafer 1995) and in ProINTA Puntal in a previous field study (Gonzalez et al.…”

Photoperiod Sensitivity during Stem Elongation as an Avenue to Raise Potential Yield in Wheat

“…2), implying some direct effects of daylength on TSI-An. Other results from controlled environments (Manupeerapan et a!., 1992;Slafer and Rawson, 1995) support this conclusion but also provide evidence for genetic variation for this response. Table I.…”

Variability in the Duration of Stem Elongation in Wheat and Barley Genotypes

“…Other studies reported in the literature have shown variability in the duration of the stem elongation phase even for similar durations of the emergence to anthesis or heading phase (Rahman and Wilson 1978, Halloran and Pennell 1982, Manupeerapan et al. 1992, Slafer and Rawson 1994, Gomez McPherson and Richards 1997, Whitechurch and Slafer 2001, 2002, Gonzalez et al.…”