Summary
A warming climate coupled with reductions in water availability and rising salinity are increasingly affecting rice (Oryza sativa) yields. Elevated temperatures combined with vapour pressure deficit (VPD) rises are causing stomatal closure, further reducing plant productivity and cooling. It is unclear what stomatal size (SS) and stomatal density (SD) will best suit all these environmental extremes.
To understand how stomatal differences contribute to rice abiotic stress resilience, we screened the stomatal characteristics of 72 traditionally bred varieties. We found significant variation in SS, SD and calculated anatomical maximal stomatal conductance (gsmax) but did not identify any varieties with SD and gsmax as low as transgenic OsEPF1oe plants.
Traditionally bred varieties with high SD and small SS (resulting in higher gsmax) typically had lower biomasses, and these plants were more resilient to drought than low SD and large SS plants, which were physically larger. None of the varieties assessed were as resilient to drought or salinity as low SD OsEPF1oe transgenic plants. High SD and small SS rice displayed faster stomatal closure during increasing temperature and VPD, but photosynthesis and plant cooling were reduced.
Compromises will be required when choosing rice SS and SD to tackle multiple future environmental stresses.
This study experimentally investigated the behaviour of concrete-filled steel tubes under cyclic axial compression. A total of 42 concrete-filled steel tube specimens of two groups were tested to failure. In each group, 18 specimens were subjected to three cyclic axial loading histories while three specimens were subjected to monotonic loading for comparison. The results indicated that concrete-filled steel tube specimens under cyclic axial compression failed in the form of buckling and still kept their form which was similar to the failure of specimens under monotonic loading. Effect of cyclic axial loading slightly reduced (approximately 2%–3%) the maximum stress but it increased 25% of the strain corresponding to the maximum stress. Loading and unloading moduli in post-peak stress phase were, respectively, about 70% and 85% higher than initial moduli because better interaction and confinement were resulted from the initial loading cycle. In addition, the absorbed energy exhibited a heavy dependence on strain and confinement while it was insignificantly affected by cyclic loading histories. Details and application of obtained experimental results are reported in this article.
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