Climate change has caused frequent extreme low-temperature events to threaten global food security. Spring low-temperature stress is one of the major limiting factors for high and stable yields of wheat. We used two wheat varieties differing in spring cold-sensitivity (cold-tolerant variety Yannong 19 and cold-sensitive variety Xinmai 26) to examine the effects of low-temperature stress during the anther differentiation period on wheat photosynthetic performance and spike-setting characteristics. Low-temperature stress was simulated in a climate box at −2 °C, 0 °C or 2 °C (night) and 15 °C (day) for 24 h, 48 h or 72 h. With the extension of the treatment time and the decrease of temperature, the photosynthetic rate, stomatal conductance and transpiration rate of wheat leaves gradually decreased. All treatments except −2 °C for 72 h recovered slowly within 7–15 days after treatment. Low-temperature stress greatly reduced grains per spikelet, 1000-grain weight and yield per plant. By analyzing the spikelets in different stalk locations (upper, middle and lower), we found that the number of upper spikelets was significantly less than lower and middle spikelets after low-temperature stress. The sterile grain of upper spikelets (Xinmai 26, for example) can reach 100% at −2 °C for 48 h and 72 h, and the yield loss rate was 90.52% at 2 °C for 24 h, which was much higher than for the lower spikelets (60.73%) and middle spikelets (50.94%). Overall, these findings suggest that low-temperature stress during the anther differentiation period alters the photosynthetic activity involved in the accumulation of dry matter in wheat, which leads to delaying young spike growth, especially for upper spikelets, and ultimately in a decrease in yield.

Due to global warming, late-spring coldness affecting wheat (LSCW) is one of the major abiotic adversities affecting wheat production. A combination of field and pot trials were conducted in this study. In the field experiment, 20 wheat varieties from the main wheat-producing areas in China were selected as experimental materials. By exploring the effects of LSCW on the spikelet characteristics and yields of different varieties, the evaluation methods and indexes of wheat varieties’ resistance to LSCW were established. Three varieties with strong resistance to LSCW (Yannong19, Guomai9, and Shannong17) and five varieties sensitive to LSCW (Zhengmai895, Xinmai26, Zhengmai366, Zhengmai8329, and Fanmai5) were screened out. The wheat varieties Yannong19 (YN19), with a strong resistance to LSCW, and Xinmai26 (XM26), with LSCW sensitivity, were selected as the test materials for the pot experiment. The ultrastructure changes in the wheat in different low-temperature treatments during the anther differentiation period were observed using an ultra-low-temperature artificial climate incubator set to 4 °C and −4 °C for 4 h (1:00–5:00 a.m.). The average temperature of the field during the low-temperature treatment was 10 °C, which was the control temperature (CK). The results showed that the cell morphology and chloroplast and mitochondrial structures of the functional leaves, young ears, and internodes below the ears were damaged, and the degree of damage was related to the cell location, the extent of low-temperature stress, and the resistance of the varieties. The degree of damage to the wheat cells was found to occur in the following order: young ears > internode belove young ears > functional leaves. The degrees of damage to the wheat cell, chloroplast, and mitochondrial structures increased with the intensification of the low-temperature stress. The damage to the XM26 variety was obviously greater than that inflicted on the YN19 variety. The anatomical mechanism of YN19 cells makes the cell structure more stable during late-spring coldness.

Considering the prevalence of cropping pattern in many Saffron cultivation regions, the continuous cropping obstacle caused the decline in growth and development. These effects justify the necessity of studying agronomic strategies to promote plant quality and production. Herein, the mono cropping, intercrop of Paulownia and Saffron, and intercrop of Soybean and Saffron patterns have been performed. The metabolites of Saffron under three cropping patterns were determined and identified using by an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. Uni and multivariate statistical analysis were applied to examine the difference between groups and select the significant differential accumulated metabolites. The results showed that a total of 315 compounds were significantly changed in three comparison groups. Phenylalanine metabolism, linoleic acid metabolism, and flavonoid biosynthesis pathway has been greatly enriched by the changed metabolites. The phenyl lactate, trans-2-Hydroxy-cinnamate, γ-Linolenate, 9-oxo-octadecadienoic acid, 13-0xo-0ctadecadienoic acid, 9,12,13-TriHOME of those metabolites showed significant differential accumulation in Saffron under three cropping patterns. And the accumulation of safranal and picrocrocin related compounds, such as Crocetin, Crocin showed a similar variation regularity. These indicate that there may be a close internal relationship between the cropping pattern and the biosynthesis of metabolites related to endogenous substances and Saffron quality formation.