Influence of leaf anatomical variation between Sorghum bicolor genotypes in response to different growth temperatures on water use efficiency

Al-Salman YMM1,2, Cano J1,2, Pan L1,2,3, Koller F1,2 and Ghannoum O1,2

  1. Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith 2751, NSW, Australia.
  2. ARC Centre of Excellence for Translational Photosynthesis, The Australian National University, Acton 2601, ACT, Australia.
  3. Sichuan Agricultural University, Sichuan Province, China.

Rising temperatures and world population will impact food security. Sorghum bicolor (great millet) is an important crop that is known for being drought-resistant. Evaluating the characteristics that enable S.bicolor to conserve water use will enable identification of traits to look for in future breeding efforts. C4 leaves of S.bicolor show improved water conservation capacity due to their carbon concentrating mechanism and high intrinsic water use efficiency (iWUE = carbon assimilation/stomatal conductance). Among the main determinants of assimilation and conductance capacities influencing WUE are the leaf’s anatomical characters. The project’s aim was to see how anatomical traits (namely leaf stomatal and vein characters) covariate and reassemble to cope with different growth temperatures in different Sorghum genotypes. Ten Sorghum genotypes were selected based on field-based variation in leaf width and water use efficiency values, and 3 plants per genotype (n=3) were grown at 3 different temperatures (22oC, 28oC, 35oC). Leaf samples from the middle of the leaf blade were cut, fixed in formaldehyde and stored in ethanol and later used for anatomical assays. Confocal microscopy was used to image the leaf surface and obtain stomatal and leaf epidermis characters. Leaves sections were also cleared and stained and scanned to obtain leaf vein characters. Anatomical data was paired with previously measured gas exchange and hydraulic conductance data to establish the relationship between anatomical variation and water use efficiency under different temperatures.