Winter warming stimulates vegetative growth and alters fruit quality of blackcurrant (Ribes nigrum).

The rate of global warming varies in magnitude between seasons, with warming being more pronounced in winter and spring than in summer and autumn at high latitudes. Winter warming can have profound effects on dormancy release and spring phenology of perennial fruit crops, but potential follow-on impacts on growth, fruit yield or quality have only rarely been investigated. We studied the effects of mild winter warming on spring phenology, current year shoot growth, cropping performance and fruit quality in four field-grown cultivars of blackcurrant with different chilling requirements. Plants were exposed to ambient or slightly elevated (+ 0.5 °C) temperatures from early October to mid-April the following year. Winter warming had few effects on spring phenology and fruit yield, but caused significant changes in berry contents of phenolic compounds and a reduction in soluble sugars. Increased vegetative growth of warmed plants likely accounts for the changes in berry quality. The results demonstrate a persistent effect of winter warming on shoot growth, which indirectly changes fruit quality.

Allopolyploidization in Cucumis contributes to delayed leaf maturation with repression of redundant homoeologous genes.

The important role of polyploidy in plant evolution is widely recognized. However, many questions remain to be explored to address how polyploidy affects the phenotype of the plant. To shed light on the phenotypic and molecular impacts of allopolyploidy, we investigated the leaf development of a synthesized allotetraploid (Cucumis × hytivus), with an emphasis on chlorophyll development. Delayed leaf maturation was identified in C. × hytivus, based on delayed leaf expansion, initial chlorophyll deficiency in the leaves and disordered sink-source transition. Anatomical observations also revealed disturbed chloroplast development in C. ×hytivus. The determination of chlorophyll biosynthesis intermediates suggested that the chlorophyll biosynthesis pathway of C. × hytivus is blocked at the site at which uroporphyrinogen III is catalysed to coproporphyrinogen III. Three chlorophyll biosynthesis-related genes, HEMA1, HEME2 and POR, were significantly repressed in C. × hytivus. Sequence alignment showed both synonymous and non-synonymous substitutions in the HEMA1, HEME2 and POR genes of the parents. Cloning of the chlorophyll biosynthetic genes suggested the retention of homoeologs. In addition, a chimeric clone of the HEMA1 gene that consisted of homologous genes from the parents was identified in C. × hytivus. Overall, our results showed that allopolyploidization in Cucumis has resulted in disturbed chloroplast development and reduced chlorophyll biosynthesis caused by the repressed expression of duplicated homologous genes, which further led to delayed leaf maturation in the allotetraploid, C. × hytivus. The preferential retention/loss of certain types of genes and non-reciprocal homoeologous recombination were also supported in the present study, which provides new insights into the impact of allopolyploidy.

Metabolic Fingerprinting of Dormant and Active Flower Primordia of Ribes nigrum Using High-Resolution Magic Angle Spinning NMR.

Global warming may modify the timing of dormancy release and spring growth of buds of temperate fruit crops. Environmental regulation of the activity-dormancy cycle in perennial plants remains poorly understood at the metabolic level. Especially, the fine-scale metabolic dynamics in the meristematic zone within buds has received little attention. In this work we performed metabolic profiling of intact floral primordia of Ribes nigrum isolated from buds differing in dormancy status using high-resolution magic angle spinning (HR-MAS) NMR. The technique proved useful in monitoring different groups of metabolites, e.g., carbohydrates and amino acids, in floral primordia and allowed metabolic separation of primordia from endo- and ecodormant buds. In addition, due to its nondestructive character, HR-MAS NMR may provide novel insights into cellular compartmentation of individual biomolecules that cannot be obtained using liquid-state NMR. Out results show that HR-MAS NMR may be an important method for metabolomics of intact plant structures.

3D Laser Triangulation for Plant Phenotyping in Challenging Environments.

To increase the understanding of how the plant phenotype is formed by genotype and environmental interactions, simple and robust high-throughput plant phenotyping methods should be developed and considered. This would not only broaden the application range of phenotyping in the plant research community, but also increase the ability for researchers to study plants in their natural environments. By studying plants in their natural environment in high temporal resolution, more knowledge on how multiple stresses interact in defining the plant phenotype could lead to a better understanding of the interaction between plant responses and epigenetic regulation. In the present paper, we evaluate a commercial 3D NIR-laser scanner (PlantEye, Phenospex B.V., Herleen, The Netherlands) to track daily changes in plant growth with high precision in challenging environments. Firstly, we demonstrate that the NIR laser beam of the scanner does not affect plant photosynthetic performance. Secondly, we demonstrate that it is possible to estimate phenotypic variation amongst the growth pattern of ten genotypes of Brassica napus L. (rapeseed), using a simple linear correlation between scanned parameters and destructive growth measurements. Our results demonstrate the high potential of 3D laser triangulation for simple measurements of phenotypic variation in challenging environments and in a high temporal resolution.

Photoperiodic variations induce shifts in the leaf metabolic profile of Chrysanthemum morifolium.

Plants have a high ability to adjust their metabolism, growth and development to changes in the light environment and to photoperiodic variation, but the current knowledge on how changes in metabolite contents are associated with growth and development is limited. We investigated the effect of three different photoperiodic treatments with similar daily light integral (DLI) on the growth responses and diurnal patterns in detected leaf metabolites in the short day plant Chrysanthemum×morifolium Ramat. Treatments were long day (LD, 18h light/6h dark), short day (SD, 12h light/12h dark) and short day with irregular night interruptions (NI-SD,12h light/12h dark, applied in a weekly pattern, shifting from day-to-day). Photoperiodic variation resulted in changes in the phenotypic development of the plants. The plants grown in the SD treatment started to initiate reproductive development of the meristems and a decrease in leaf expansion resulted in lower leaf area of expanding leaves. In contrast, plants in the NI-SD and LD treatments did not show reproductive development at any stage and final leaf area of the expanding leaves was intermediate for the NI-SD plants and largest for the LD plants. Photoperiodic variation also resulted in changes in the leaf metabolic profile for most of the analysed metabolites, but only carbohydrates, citrate and some amino acids displayed a shift in their diurnal pattern. Further, our results illustrated that short days (SD) increased the diurnal turnover of 1-kestose after 2 weeks, and decreased the overall contents of leaf hexoses after 3 weeks. In the two other treatments a diurnal turnover of 1-kestose was not stimulated before after 3 weeks, and hexoses together with the hexose:sucrose ratio steadily increased during the experiment. Our results enlighten the plasticity of leaf growth and metabolism to environmental changes, and demonstrate that diurnally regulated metabolites not always respond to photoperiodic variation.

Rapid adjustment in chrysanthemum carbohydrate turnover and growth activity to a change in time-of-day application of light and daylength.

Diel (24h) rhythms are believed to be of great importance to plant growth and carbohydrate metabolism in fluctuating environments. However, it is unclear how plants that have evolved to experience regular day-night patterns will respond to irregular light environments that disturb diurnally-regulated parameters related to growth. In this study, chrysanthemum plants were exposed to a change in the time-of-day application of light followed by short days or long days with a night interruption of light. We observed a clear shift in the diel cycle of sucrose turnover and relative leaf expansion, indicating a resetting of these activities with a temporal trigger in the early morning. The starch pool was relatively stable in long-day plants and marginally affected by the change in the time-of-day application in light followed by long days with a night interruption. This was in contrast with an onset of a daily starch turnover by a shift to short days. These results confirm findings from model species on the complex relationship between carbohydrate metabolism, source-sink relations and growth rate and they shed new light on the dynamic processes during acclimation towards altered environmental responses of plants in fluctuating environments.