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Crop productivity can be expressed as the product of the amount of radiation intercepted, radiation use efficiency and harvest index. Genetic variation for components of radiation use efficiency has rarely been explored due to the lack of appropriate equipment to determine parameters at the scale needed in plant breeding. On the other hand, responses of the photosynthetic apparatus to environmental conditions have not been extensively investigated under field conditions, due to the challenges posed by the fluctuating environmental conditions. This study applies a rapid, low-cost, and reliable high-throughput phenotyping tool to explore genotypic variation for photosynthetic performance of a set of hybrid barleys and their parents under mild water-stress and unstressed field conditions. We found differences among the genotypic sets that are relevant for plant breeders and geneticists. Hybrids showed lower leaf temperature differential and higher non-photochemical quenching, resembling closer the male parents. The combination of traits detected in hybrids seems favorable, and could indicate improved photoprotection and better fitness under stress conditions. Additionally, we proved the potential of a low-cost, field-based phenotyping equipment to be used routinely in barley breeding programs for early screening for stress tolerance.

In flowering plants, homologs of the Arabidopsis phosphatidylethanolamine-binding protein (PEBP) FLOWERING LOCUS T (FT) are key components in controlling flowering time. We show here that, although FT homologs are found in all angiosperms with completed genome sequences, there is no evidence to date that FT-like genes exist in other groups of plants. Through phylogeny reconstructions and heterologous expression, we examined the biochemical function of the Picea (spruces) and Pinus (pines) PEBP families two gymnosperm taxa phylogenetically distant from the angiosperms. We have defined a lineage of gymnosperm PEBP genes, termed the FT/TERMINAL FLOWER1 (TFL1)-like genes, that share sequence characteristics with both the angiosperm FT- and TFL1-like clades. When expressed in Arabidopsis, FT/TFL1-like genes repressed flowering, indicating that the proteins are biochemically more similar to the angiosperm TFL1-like proteins than to the FT-like proteins. This suggests that the regulation of the vegetative-to-reproductive switch might differ in gymnosperms compared with angiosperms. Molecular evolution studies suggest that plasticity at exon 4 contributes to the divergence of FT-like function in floral promotion. In addition, the presence of FT-like genes in basal angiosperms indicates that the FT-like function emerged at an early stage during the evolution of flowering plants as a means to regulate flowering time.