Background Many agronomic traits have been bred into modern wheat varieties, but wheat ( Triticum aestivum L.) continues to be vulnerable to heat stress, with high night-time temperature (HNT) stress shown to have large negative impact on yield and quality. Global mean temperature during the day is consistently warming with the minimum night temperature increasing at a much quicker pace. Currently, there is no system or method that allows crop scientists to impose HNT stress at key developmental stages on wheat or crops in general under field conditions, involving diverse genotypes and maintaining a dynamic temperature differential within the tents compared to the outside. Results Through implementation of a side roll up and a top ventilation system, heaters, and a custom cyber-physical system using a Raspberry Pi, the heat tents were able to consistently maintain an elevated temperature through the night to differentiate heat stress impact on different genotypes. When the tents were placed in their day-time setting they were able to maintain ambient day-time temperature without having to be removed and replaced on the plots. Data averaged from multiple sensors over three consecutive weeks resulted in a consistent but small temperature difference of 0.25 °C within the tents, indicating even distribution of heat. While targeting a temperature differential of 4 °C, the tents were able to maintain an average differential of 3.2 °C consistently throughout the night-time heat stress period, compared to the outside ambient conditions. The impact of HNT stress was confirmed through a statistically significant yield reduction in eleven of the twelve genotypes tested. The average yield under HNT stress was reduced by 20.3% compared to the controls, with the highest reduction being 41.4% and a lowest reduction of 6.9%. Recommendations for fine-tuning the system are provided. Conclusion This methodology is easily accessible and can be widely utilized due to its flexibility and ease of construction. This system can be modified and improved based on some of the recommendations and has the potential to be used across other crops or plants as it is not reliant on access to any hardwired utilities. The method tested will help the crop community to quantify the impact of HNT stress, identify novel donors that induce tolerance to HNT and help the breeders develop crop varieties that are resilient to changing climate. Electronic supplementary material The online version of this article (10.1186/s13007-019-0424-x) contains supplementary material, which is available to authorized users.

Winter wheat (Triticum aestivum L.) is essential to maintain food security for a large proportion of the world’s population. With increased risk from abiotic stresses due to climate variability, it is imperative to understand and minimize the negative impact of these stressors, including high night temperature (HNT). Both globally and at regional scales, a differential rate of increase in day and night temperature is observed, wherein night temperatures are increasing at a higher pace and the trend is projected to continue into the future. Previous studies using controlled environment facilities and small field-based removable chambers have shown that post-anthesis HNT stress can induce a significant reduction in wheat grain yield. A prototype was previously developed by utilizing field-based tents allowing for simultaneous phenotyping of popular winter wheat varieties from US Midwest and advanced breeding lines. Hence, the objectives of the study were to (i) design and build a new field-based infrastructure and test and validate the uniformity of HNT stress application on a scaled-up version of the prototype (ii) improve and develop a more sophisticated cyber-physical system to sense and impose post-anthesis HNT stress uniformly through physiological maturity within the scaled-up tents; and (iii) determine the impact of HNT stress during grain filling on the agronomic and grain quality parameters including starch and protein concentration. The system imposed a consistent post-anthesis HNT stress of + 3.8 °C until maturity and maintained uniform distribution of stress which was confirmed by (i) 0.23 °C temperature differential between an array of sensors within the tents and (ii) statistically similar performance of a common check replicated multiple times in each tent. On average, a reduction in grain-filling duration by 3.33 days, kernel weight by 1.25% per °C, grain number by 2.36% per °C and yield by 3.58% per °C increase in night temperature was documented. HNT stress induced a significant reduction in starch concentration indicating disturbed carbon balance. The pilot field-based facility integrated with a robust cyber-physical system provides a timely breakthrough for evaluating HNT stress impact on large diversity panels to enhance HNT stress tolerance across field crops. The flexibility of the cyber-physical system and movement capabilities of the field-based infrastructure allows this methodology to be adaptable to different crops.

When the phase velocity of light in a moving medium is used to predict the phase velocity of that light relative to a stationary observer then the Einstein low speed approximation to his velocity addition equation and the Fresnel drag equation both predict the exact same result. Therefore existing interference fringe shift experiments do not differentiate between the Fresnel and Einstein predictions. However, when the group velocity of light is used, the Fresnel prediction and the Einstein prediction are different. When Fresnel predictions based on group velocity are made for the proposed experiment, the difference in round trip arrival times for the two halves of a split laser pulse is substantial. When Einstein predictions based on group velocity are made the difference in round trip times is, of course, zero. Thus a positive result for the proposed experiment would violate Special Relativity Theory (SRT) with regards to the relativity of simultaneity and suggest that the Lorentz-Poincare' physical viewpoint on the SRT equations is a better viewpoint.If the Einstein prediction for group velocity is not correct, then when positive data for the experiment configuration shown in Figure 1.0 is collected at various orientations at different times of the day it is possible to identify a local preferred reference frame in which the speed of light is actually (not just apparently) isotropic. This reference frame could be used in place of star reference frames for spacecraft navigation. Other implications of a local preferred reference frame are explained in the paper.

Background and objectives: Wheat (Triticum aestivum L.) is highly vulnerable to heat stress during sensitive growth and developmental stages, including grainfilling. The impact of high daytime heat stress on wheat yield and quality losses has been extensively investigated, while information related to high night-time temperature (HNT) is limited. The major objective was to ascertain the changes in wheat grain macro-and micro-nutrient composition and yield-related parameters on exposure to HNT during grain-filling. Twelve diverse genotypes were grown in field-based custom-built heat tents that allowed natural light and temperature conditions during the day and imposed stress overnight. Findings:The field-tents imposed a 3.2°C higher night-time temperature compared to ambient conditions throughout the grain-filling period. HNT stress reduced 200 grain weight by 1.9%, grain yield by 3.1%, seed starch content by 2.5%, and seed protein content by 3.6% per °C increase in HNT. Conclusions:HNT had significant negative effect on grain macro-and micronutrient content. However, starch and protein concentrations were differentially correlated with grain nutrients, with starch negatively correlated with many of the micronutrients under control and HNT.Significance and novelty: This negative correlation highlights the imperative balance of seed micronutrient composition that needs to be maintained as efforts are intensified to enhance grain yield under favorable and warming environments.

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Scleraxis is a basic helix-loop-helix (bHLH) transcription factor shown previously to be expressed in developing chondrogenic cell lineages during embryogenesis. To investigate its function in embryonic development, we produced scleraxis-null mice by gene targeting. Homozygous mutant embryos developed normally until the early egg cylinder stage (embryonic day 6.0), when they became growth-arrested and failed to gastrulate. Consistent with this early embryonic phenotype, scleraxis was found to be expressed throughout the embryo at the time of gastrulation before becoming restricted to chondrogenic precursor cells at embryonic day 9.5. At the time of developmental arrest, scleraxis-null embryos consisted of ectodermal and primitive endodermal cell layers, but lacked a primitive streak or recognizable mesoderm. Analysis of molecular markers of the three embryonic germ layers confirmed that scleraxis mutant embryos were unable to form mesoderm. By generating chimeric embryos, using lacZ-marked scleraxis-null and wild-type embryonic stem cells, we examined the ability of mutant cells to contribute to regions of the embryo beyond the time of lethality of homozygous mutants. Scleraxis-null cells were specifically excluded from the sclerotomal compartment of somites, which gives rise to the axial skeleton, and from developing ribs, but were able to contribute to most other regions of the embryo, including mesoderm-derived tissues. These results reveal an essential early role for scleraxis in mesoderm formation, as well as a later role in formation of somite-derived chondrogenic lineages, and suggest that scleraxis target genes mediate these processes.

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