Dark respiration rates are not determined by differences in mitochondrial capacity, abundance and ultrastructure in C leaves.

Our understanding of the regulation of respiration in C plants, where mitochondria play different roles in the different types of C photosynthetic pathway, remains limited. We examined how leaf dark respiration rates (R ), in the presence and absence of added malate, vary in monocots representing the three classical biochemical types of C photosynthesis (NADP-ME, NAD-ME and PCK) using intact leaves and extracted bundle sheath strands. In particular, we explored to what extent rates of R are associated with mitochondrial number, volume and ultrastructure.

Auxetic vibration behaviours of periodic tetrahedral units with a shared edge.

A very low-frequency mode supported within an auxetic structure is presented. We propose a constrained periodic framework with corner-to-corner and edge-to-edge sharing of tetrahedra and develop a kinematic model incorporating two types of linear springs to calculate the momentum term under infinitesimal transformations. The modal analysis shows that the microstructure with its two degrees of freedom has both low- and high-frequency modes under auxetic transformations.

The crucial roles of mitochondria in supporting C photosynthesis.

C photosynthesis involves a series of biochemical and anatomical traits that significantly improve plant productivity under conditions that reduce the efficiency of C photosynthesis. We explore how evolution of the three classical biochemical types of C photosynthesis (NADP-ME, NAD-ME and PCK types) has affected the functions and properties of mitochondria. Mitochondria in C NAD-ME and PCK types play a direct role in decarboxylation of metabolites for C photosynthesis.

Acclimation of leaf respiration temperature responses across thermally contrasting biomes.

Short-term temperature response curves of leaf dark respiration (R-T) provide insights into a critical process that influences plant net carbon exchange. This includes how respiratory traits acclimate to sustained changes in the environment. Our study analysed 860 high-resolution R-T (10-70°C range) curves for: (a) 62 evergreen species measured in two contrasting seasons across several field sites/biomes; and (b) 21 species (subset of those sampled in the field) grown in glasshouses at 20°C : 15°C, 25°C : 20°C and 30°C : 25°C, day : night.