Spike differentiation is important for reproductive organ formation during wheat growth and development, and is a crucial period influencing grain yield. Spike differentiation depends not only on genetic characteristics but also environmental factors such as temperature. In recent years, rising temperatures and extreme weather associated with global climate change have strongly affected agricultural production and systems.
Wheat is an important food crop worldwide and is the main crop grown in Henan province. With the aim of assessing the effects of increasing temperature on wheat spike differentiation, a comparative study of wheat spike differentiation in the glasshouse and field was conducted during 2009/2010. The experimental material comprised 'Zhengmai 9023’, which is a semi-spring wheat cultivar, and 'Zhoumai 18’, which is a semi-winter wheat cultivar. In the field experiment, seeds were sown on 18 October; in the glasshouse experiment, seeds were sown on 1 November (T₁), 15 November (T₂) and 29 November (T₃). Spike development was observed with a stereomicroscope from seedling emergence until completion of anther differentiation, and the effects of temperature on spike differentiation were studied.
The mean temperature and accumulated temperature above zero tended to be higher in the glasshouse than in the field during the whole growth period. Wheat plants underwent normal spike differentiation and attained maturity in the glasshouse, but the duration of the spike differentiation process was significantly shorter in the glasshouse than in the field (P < 0.01). Therefore, the entire growth period was also shorter in the glasshouse than in the field. The spike differentiation process was accelerated with increasing temperature and accumulated temperature above zero. Compared with the field environment, the spike differentiation stages of significantly shorter duration in the glasshouse were early developmental stages from seedling emergence to the spike elongation, single ridge and double ridge stages. In the glasshouse, with the sowing time delayed (T₂ and T₃), the duration of spike differentiation was shortened, the onset of each spike differentiation stage was delayed, and the accumulated temperature during the entire spike differentiation period was lower. The duration of spike differentiation under the T₁ treatment was significantly longer than that under the T₂ treatment (P < 0.01).
Differences in spike differentiation between the two cultivars were apparent. In this study, the duration of spike differentiation was shorter, and the onset of each developmental stage was earlier, in Zhengmai 9023 compared with those of Zhoumai 18. The effects of temperature on spike differentiation differed between the cultivars. The accumulated temperature during spike differentiation for Zhengmai 9023 was lower than that of Zhoumai 18 sown at the same time. For Zhengmai 9023, high temperature mostly influenced the intermediate developmental stages, namely the double ridge, glume differentiation, and floret differentiation stages. For Zhoumai 18, early and late developmental stages were mainly affected by high temperature, namely the single ridge, double ridge and anther differentiation stages. The influence of accumulated temperature was strongest on the glume differentiation stage in Zhengmai 9023, and on the anther differentiation and double ridge stages in Zhoumai 18.