Salinity tolerance-associated phenotypes of 35 EMS mutagenized wheat lines originating from BARI Gom-25 were compared. Vegetative growth was measured using non-destructive image-based phenotyping. Five different NaCl concentrations (0 to 160 mM) were applied to plants 19 days after planting (DAP 19), and plants were imaged daily until DAP 38. Plant growth, water use, leaf Na⁺, K⁺ and Cl⁻ content, and thousand kernel weight (TKW) were measured, and six lines were selected for further analysis. In saline conditions, leaf Na⁺, K^+, and Cl⁻ content variation on a dry weight basis within these six lines were ~9.3, 1.4, and 2.4-fold, respectively. Relative to BARI Gom-25, two (OA6, OA62) lines had greater K⁺ accumulation, three (OA6, OA10, OA62) had 50–75% lower Na⁺:K⁺ ratios, and OA62 had ~30% greater water-use index (WUI). OA23 had ~2.2-fold greater leaf Na⁺ and maintained TKW relative to BARI Gom-25. Two lines (OA25, OA52) had greater TKW than BARI Gom-25 when grown in 120 mM NaCl but similar Na⁺:K⁺, WUI, and biomass accumulation. OA6 had relatively high TKW, high leaf K^+, and WUI, and low leaf Na⁺ and Cl⁻. Phenotypic variation revealed differing associations between the parameters measured in the lines. Future identification of the genetic basis of these differences, and crossing of lines with phenotypes of interest, is expected to enable the assessment of which combinations of parameters deliver the greatest improvement in salinity tolerance.

Grain protein content (GPC) is a key quality attribute and an important marketing trait in wheat. In the current cropping systems worldwide, GPC is mostly determined by nitrogen (N) fertilizer application. The objectives of this study were to understand the differences in N response between high and low GPC wheat genotypes, and to assess the value of biomass growth analysis to assess the differences in N response. Six wheat genotypes from a range of high to low GPC were grown in low, medium and high N, under glasshouse conditions. This experiment was designed around non-destructive estimation of biomass using a high throughput image-based phenotyping system. Results showed that Spitfire and Mace had higher grain N% than Gazelle and QAL2000, and appeared to demand more N to grow their biomass. Moreover, at low N, Spitfire grew faster and achieved the maximum absolute growth rate earlier than high N-treated plants. High grain N% genotypes seem able to manage grain N reserves by compromising biomass production at low N. This study also indicated the importance of biomass growth analysis to show the differences in the N responsiveness of high and low GPC wheat.

In recent years, topological concepts have yielded valuable insights into the long standing problem of laminar fluid mixing. Topologically complex stirring protocols are typically far superior to topologically simple protocols, guaranteeing chaotic advection of fluid particles and the associated exponential dilation of material elements. Furthermore, topological approaches to mixer design are typically intuitive and insensitive to precise geometry or fluid properties. However, results to date have been limited to two dimensional flows (for example, batch stirrers in food or polymer manufacturing) and quasi three dimensional protocols (for example, continuous flow micromixers). Motivated by a simple stretching and folding argument that works well in two dimensions, we propose a topological approach to fully three dimensional fluid mixing. A transition matrix is derived to describe the mapping induced by a three dimensional `braid' on area elements, and the associated Perron--Frobenius eigenvalue provides a prediction of the large time asymptotic area growth rate. We show that these theoretical predictions agree well with numerical data obtained from simulations in a prototype three dimensional mixing device. References M. Bestvina and M. Handel. Train tracks for surface homeomorphisms, Topology 34, 1995, 109--140. doi:10.1016/0040-9383(94)E0009-9 P. L. Boyland, H. Aref and M. A. Stremler. Topological fluid mechanics of stirring, J. Fluid Mech., 403, 2000, 277--304. doi:10.1017/S0022112099007107 J. Chen and M. A. Stremler. Topological chaos and mixing in three dimensional channel flow. {Physics of Fluids}, 21, 2009, 021701. doi:10.1063/1.3076247 M. D. Finn and J.--L. Thiffeault. Topological entropy of braids on the torus. SIAM J. Appl. Dyn. Sys., 6, 2007, 79--98. doi:10.1137/060659636 O. S. Galaktionov, P. D. Anderson, G. M. W. Peters and F. N. van de Vosse. An adaptive front tracking technique for three dimensional transient flows. Int. J. Numer. Meth. Fluids, 32, 2000, 201--217. E. Gouillart, N. Kuncio, O. Dauchot, B. Dubrulle, S. Roux and J.--L. Thiffeault. Walls inhibit chaotic mixing. Phys. Rev. Lett. 99, 2007, 114501. T. G. Kang, M. K. Singh, T. H. Kwon and P. D. Anderson. Chaotic mixing using periodic and aperiodic sequences of mixing protocols in a micromixer. Microfluid Nanofluid, 4, 2008, 589--99. doi:10.1007/s10404-007-0004-x J.--O. Moussafir. On computing the entropy of braids. Func. Anal. Other Math., 1, 2006, 37--46. doi:10.1007/s11853-007-0206-z H. A. Stone and S. Kim. Microfluidics: basic issues, applications and challenges. American Institute of Chemical Engineers Journal, 47, 2001, 1250--54. doi:10.1002/aic.690470602 M. A. Stremler and J. Chen. Generating topological chaos in lid driven cavity flow, Physics of Fluids, 19, 2007, 103602. doi:10.1063/102772881 M. A. Stremler, F. R. Haselton and H. Aref. Designing for chaos: applications of chaotic advection at the microscale. Phil. Trans. R. Soc. Lond. A, 362, 2004, 1019--36. J.-L. Thiffeault and M. D. Finn. Topology, braids and mixing in fluids. Phil. Trans. R. Soc. Lond. A, 364, 2006, 3251--66. doi:10.1098/rsta.2006.1899 C. R. Thomas. Problems of shear in biotechnology. Critical Reports on Applied Chemistry, 29, 1990, 23--93. S. O. Unverdi and G. Tryggvason. A front tracking method for viscous, incompressible, multi-fluid fluids. J. Comp. Phys., 100, 1992, 25--37. G. M. Whitesides and A. D. Stroock. Flexible methods for microfluidics. Physics Today, 54, 2001, 42--48.

Wheat ( Triticum aestivum L.) production is increasingly challenged by simultaneous drought and heatwaves. We assessed the effect of both stresses combined on whole plant water use and carbohydrate partitioning in eight bread wheat genotypes that showed contrasting tolerance. Plant water use was monitored throughout growth, and water-soluble carbohydrates (WSC) and starch were measured following a three-day heat treatment during drought. WSC were predominantly allocated to the spike in modern Australian varieties, whereas the stem contained most WSC in older genotypes. Combined drought and heat stress increased WSC partitioning to the spike in older genotypes but not in the modern varieties. Glucose and fructose concentrations in grains measured 12 days after anthesis were associated with final grain weight in the main spike. At the whole plant level, combined drought and heat stress differentially altered daily water use and transpiration response to vapour pressure deficit during grain filling, compared to drought only. Final grain yield was increasingly associated with aboveground biomass and total water use with increasing stress intensity. Ability to maintain transpiration, especially following combined drought and heat stress, appears essential for maintaining wheat productivity. One sentence summary: Higher yield following drought and heat stress in wheats that maintain transpiration and have higher water-soluble carbohydrates content in grains.