The timing of plant reproduction has a large impact on yield in crop plants. Reproductive development in temperate cereals comprises two major developmental transitions. During spikelet initiation, the identity of the shoot meristem switches from the vegetative to the reproductive stage and spikelet primordia are formed on the apex. Subsequently, floral morphogenesis is initiated, a process strongly affected by environmental variation. Recent studies in cereal grasses have suggested that this later phase of inflorescence development controls floret survival and abortion, and is therefore crucial for yield. Here, we provide a synthesis of the early morphological and the more recent genetic studies on shoot development in wheat and barley. The review explores how photoperiod, abiotic stress, and nutrient signalling interact with shoot development, and pinpoints genetic factors that mediate development in response to these environmental cues. We anticipate that research in these areas will be important in understanding adaptation of cereal grasses to changing climate conditions.

Stress impacts negatively on plant growth and crop productivity, caicultural production worldwide. Throughout their life, plants are often confronted with multiple types of stress that affect overall cellular energy status and activate energy-saving responses. The resulting low energy syndrome (LES) includes transcriptional, translational, and metabolic reprogramming and is essential for stress adaptation. The conserved kinases sucrose-non-fermenting-1-related protein kinase-1 (SnRK1) and target of rapamycin (TOR) play central roles in the regulation of LES in response to stress conditions, affecting cellular processes and leading to growth arrest and metabolic reprogramming. We review the current understanding of how TOR and SnRK1 are involved in regulating the response of plants to low energy conditions. The central role in the regulation of cellular processes, the reprogramming of metabolism, and the phenotypic consequences of these two kinases will be discussed in light of current knowledge and potential future developments.

BackgroundGrowth is an important parameter to consider when studying the impact of treatments or mutations on plant physiology. Leaf area and growth rates can be estimated efficiently from images of plants, but the experiment setup, image analysis, and statistical evaluation can be laborious, often requiring substantial manual effort and programming skills.ResultsHere we present rosettR, a non-destructive and high-throughput phenotyping protocol for the measurement of total rosette area of seedlings grown in plates in sterile conditions. We demonstrate that our protocol can be used to accurately detect growth differences among different genotypes and in response to light regimes and osmotic stress. rosettR is implemented as a package for the statistical computing software R and provides easy to use functions to design an experiment, analyze the images, and generate reports on quality control as well as a final comparison across genotypes and applied treatments. Experiment procedures are included as part of the package documentation.ConclusionsUsing rosettR it is straight-forward to perform accurate, reproducible measurements of rosette area and relative growth rate with high-throughput using inexpensive equipment. Suitable applications include screening mutant populations for growth phenotypes visible at early growth stages and profiling different genotypes in a wide variety of treatments.

FLOWERING LOCUS T-like genes (FT-like) control the photoperiodic regulation of flowering in many angiosperm plants. The family of FT-like genes is characterised by extensive gene duplication and subsequent diversification of FT functions which occurred independently in modern angiosperm lineages. In barley, there are 12 known FT-like genes (HvFT) but the function of most of them remains uncharacterised. This study aimed to characterise the role of HvFT4 in flowering time control and development in barley. The overexpression of HvFT4 in the spring cultivar Golden Promise delayed flowering time under long-day conditions. Microscopic dissection of the shoot apical meristem (SAM) revealed that overexpression of HvFT4 specifically delayed spikelet initiation and reduced the number of spikelet primordia and grains per spike. Furthermore, ectopic overexpression of HvFT4 was associated with floret abortion and with the downregulation of the barley MADS-box genes VRN-H1, HvBM3 and HvBM8 which promote floral development. This suggests that HvFT4 functions as a repressor of reproductive development in barley. Unraveling the genetic basis of FT-like genes can contribute to the identification of novel breeding targets to modify reproductive development and thereby spike morphology and grain yield.

21 FLOWERING LOCUS T-like genes (FT-like) control the photoperiodic regulation of flowering 22 in many angiosperm plants. The family of FT-like genes is characterised by extensive gene 23 duplication and subsequent diversification of FT functions which occurred independently in 24 modern angiosperm lineages. In barley, there are 12 known FT-like genes (HvFT) but the 25 function of most of them remains uncharacterised. This study aimed to characterise the role of 26 HvFT4 in flowering time control and development in barley. The overexpression of HvFT4 in 27 the spring cultivar Golden Promise delayed flowering time under long-day conditions. 28 Microscopic dissection of the shoot apical meristem (SAM) revealed that overexpression of 29 HvFT4 specifically delayed spikelet initiation and reduced the number of spikelet primordia 30 and grains per spike. Furthermore, ectopic overexpression of HvFT4 was associated with floret 31 abortion and with the downregulation of the barley MADS-box genes VRN-H1, HvBM3 and 32 HvBM8 which promote floral development. This suggests that HvFT4 functions as a repressor 33 of reproductive development in barley. Unraveling the genetic basis of FT-like genes can 34 contribute to the identification of novel breeding targets to modify reproductive development 35 and thereby spike morphology and grain yield. 36