Source-to-sink transport of sugar is one of the major determinants of plant growth and relies on the efficient and controlled distribution of sucrose (and some other sugars such as raffinose and polyols) across plant organs through the phloem. However, sugar transport through the phloem can be affected by many environmental factors that alter source/sink relationships. In this paper, we summarize current knowledge about the phloem transport mechanisms and review the effects of several abiotic (water and salt stress, mineral deficiency, CO₂, light, temperature, air, and soil pollutants) and biotic (mutualistic and pathogenic microbes, viruses, aphids, and parasitic plants) factors. Concerning abiotic constraints, alteration of the distribution of sugar among sinks is often reported, with some sinks as roots favored in case of mineral deficiency. Many of these constraints impair the transport function of the phloem but the exact mechanisms are far from being completely known. Phloem integrity can be disrupted (e.g., by callose deposition) and under certain conditions, phloem transport is affected, earlier than photosynthesis. Photosynthesis inhibition could result from the increase in sugar concentration due to phloem transport decrease. Biotic interactions (aphids, fungi, viruses…) also affect crop plant productivity. Recent breakthroughs have identified some of the sugar transporters involved in these interactions on the host and pathogen sides. The different data are discussed in relation to the phloem transport pathways. When possible, the link with current knowledge on the pathways at the molecular level will be highlighted.

Plant growth and development has to be continuously adjusted to the available resources. Their optimization requires the integration of signals conveying the plant metabolic status, its hormonal balance, and its developmental stage. Many investigations have recently been conducted to provide insights into sugar signaling and its interplay with hormones and nitrogen in the fine-tuning of plant growth, development, and survival. The present review emphasizes the diversity of sugar signaling integrators, the main molecular and biochemical mechanisms related to the sugar-signaling dependent regulations, and to the regulatory hubs acting in the interplay of the sugar-hormone and sugar-nitrogen networks. It also contributes to compiling evidence likely to fill a few knowledge gaps, and raises new questions for the future.

Natural fibres such as hemp are extensively used in new composite materials. This article deals with biological and mechanical aspects of hemp phloem fibres. The effects of different cultural parameters on some characteristics of hemp fibres were studied: variety, soil drought during plant cultivation and water-retting process. Results showed that there was no significant influence on studied properties of the hemp variety and of water-retting. Under water-limited conditions, results showed that plant growth was reduced and the maturation of phloem fibres was delayed. Secondary cell wall was synthesised later in comparison with water-controlled conditions and cell protoplast remains longer. These biological aspects can be related to the higher Young’s modulus and maximal stress values measured on fibre strands from plants grown under water-stressed conditions. These results are promising, by considering the extent and degree of drought conditions in the world.

Drought is one of the main abiotic stresses, which affects plant growth, development, and crop yield. Plant response to drought implies carbon allocation to sink organs and sugar partitioning between different cell compartments, and thereby requires the involvement of sugar transporters (SUTs). Among them, the early response to dehydration six-like (ESL), with 19 members in Arabidopsis thaliana, form the largest subfamily of monosaccharide transporters (MSTs) still poorly characterized. A common feature of these genes is their involvement in plant response to abiotic stresses, including water deficit. In this context, we carried out morphological and physiological phenotyping of A. thaliana plants grown under well-watered (WW) and water-deprived (WD) conditions, together with the expression profiling of 17 AtESL genes in rosette leaves. The drought responsiveness of 12 ESL genes, 4 upregulated and 8 downregulated, was correlated to different water statuses of rosette leaves. The differential expression of each of the tandem duplicated AtESL genes in response to water stress is in favor of their plausible functional diversity. Furthermore, transfer DNA (T-DNA) insertional mutants for each of the four upregulated ESLs in response to water deprivation were identified and characterized under WW and WD conditions. To gain insights into global sugar exchanges between vacuole and cytosol under water deficit, the gene expression of other vacuolar SUTs and invertases (AtTMT, AtSUC, AtSWEET, and AtβFRUCT) was analyzed and discussed.

Background: Wildfires are a growing threat, especially in Mediterranean climate areas during periods of drought. The wildfire research community continues to investigate propagation mechanisms considering thermal transfer and fluid mechanics and sometimes a simplified chemistry taking into account the main combustion products such as CO, CO2, H2O, H2 and CH4. However, volatile organic compounds (VOCs) cannot be neglected and have a major role in vegetation ignition. Despite this, knowledge on the influence of wildfire on plant emissions remains lacking. Aims: This work addresses the effect of combined hydric and thermal stresses on the physiology and emissions of Rosmarinus officinalis and Cistus albidus, which are widely consumed in Mediterranean wildfires. Methods: Plants were submitted to hydric stress inside a greenhouse, then to thermal stress inside a heated hermetic enclosure while collecting emissions with adsorbent elements for analysis. Simultaneously, heating experiments were carried out with leaves sampled to analyse their emissions. Key results: The heating tests showed significant variations in monoterpene, fatty acid and alkane emissions between stressed and unstressed plants with different results between Rosmarinus officinalis and Cistus albidus. Conclusion/implication: Further experiments with other plant species and quantification of emissions may help to better know why Mediterranean wildfires are a particular threat and how to improve firefighting methods.