The Effect of Ambient Temperature on Brachypodium distachyon Development

Abstract

Due to climate change, the effect of temperature on crops has become a global concern. It has been reported that minor changes in temperature can cause large decreases in crop yield. While not a crop, the model Brachypodium distachyon can help to efficiently investigate ambient temperature responses of temperate grasses, which include wheat and barley. Here, we use different accessions to explore the effect of ambient temperature on Brachypodium phenology. We recorded leaf initiation, heading time, leaf and branch number at heading, seed set time, seed weight, seed size, seed dormancy, and seed germination at different temperatures. We found that warmer temperatures promote leaf initiation so that leaf number at heading is positively correlated to temperature. Heading time is not correlated to temperature but accessions show an optimal temperature at which heading is earliest. Cool temperatures prolong seed maturation which increases seed weight. The progeny seeds of plants grown at these cool ambient temperatures show stronger dormancy, while imbibition of seeds at low temperature improves germination. Among all developmental stages, it is the duration of seed maturation that is most sensitive to temperature. The results we found reveal that temperature responses in Brachypodium are highly conserved with temperate cereals, which makes Brachypodium a good model to explore temperature responsive pathways in temperate grasses.

Keywords: ambient temperature; heading time; seed dormancy; seed maturation time; seed weight.

FIGURE 1

Local climate information for natural accessions of Brachypodium. Data from New LocClim software (Grieser et al., 2006). (A) Locations of different accessions. (B–E) Average precipitation (bar chart) and average temperature (line) of the whole year for each accession.

FIGURE 2

Leaf development in the vegetative stage at different temperatures. (A–D) Leaf numbers at 26°C (black circle) and 18°C (black square) for different accessions. (E,F) The leaf initiation rate at 18 and 26°C in different accessions. Student test was used for statistically analysis and ^∗∗adjusted P < 0.01.

FIGURE 3

Trait effects during the reproductive stage at 14, 18, and 22°C. Left panels (A,D,G,J,M,P) phenotype data for different accessions for heading time, leaf number at heading, branch number at heading, seed set time, seed weight per 50 seeds and seed area. Middle panels (B,E,H,K,N,Q) correlation between traits and temperatures. Right panels (C,F,I,L,O,R) log (Q10) for different traits in different accessions. One-way ANOVA was used for statistically analysis and ^*adjusted P < 0.05, ^∗∗adjusted P < 0.01. NA, missing data.

FIGURE 4

The effect of different temperatures on seed dormancy. (A) Germination percentage of seeds (Bd21, Bd21-3, Mon3, BdTR3C, and Bd1-1) produced at 14°C (white bar), 18°C (gray bar), and 22°C (black bar) incubated at 12°C. (B) Germination rate index of seeds (physiologically mature seeds (PM), 2-week physiologically mature seeds (PM + 2) and 4-week physiologically mature seeds (PM + 4) from twenty natural accessions were incubated at 12°C (gray bar) and 24°C (black bar). The accessions information mentioned in Supplementary Table S1. One-way ANOVA was used for statistically analysis and ^*adjusted P < 0.05, ^∗∗adjusted P < 0.01.

FIGURE 5

Summary for the timing of average emergence to heading, average heading to physiologically mature seed and average seed germination time (12°C) of five accessions (Bd21, Bd21-3, Mon3, BdTR3C, and Bd1-1) at 14, 18, and 22°C.