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<jats:p>Acclimation of photosynthesis to light intensity (photoacclimation) takes days to achieve and so naturally fluctuating light presents a potential challenge where leaves may be exposed to light conditions that are beyond their window of acclimation. Experiments generally have focused on unchanging light with a relatively fixed combination of photosynthetic attributes to confer higher efficiency in those conditions. Here a controlled LED experiment and mathematical modelling was used to assess the acclimation potential of contrasting Arabidopsis thaliana genotypes following transfer to a controlled fluctuating light environment, designed to present frequencies and amplitudes more relevant to natural conditions. We hypothesize that acclimation of light harvesting, photosynthetic capacity and dark respiration are controlled independently. Two different ecotypes were selected, Wassilewskija-4 (Ws), Landsberg erecta (Ler) and a GPT2 knock out mutant on the Ws background (gpt2-), based on their differing abilities to undergo dynamic acclimation i.e. at the sub-cellular or chloroplastic scale. Results from gas exchange and chlorophyll content indicate that plants can independently regulate different components that could optimize photosynthesis in both high and low light; targeting light harvesting in low light and photosynthetic capacity in high light. Empirical modelling indicates that the pattern of ‘entrainment’ of photosynthetic capacity by past light history is genotype-specific. These data show flexibility of photoacclimation and variation useful for plant improvement.</jats:p>

<jats:p>Many areas of sugar beet production will face hotter and drier summers as the climate changes. There has been much research on drought tolerance in sugar beet but water use efficiency (WUE) has been less of a focus. An experiment was undertaken to examine how fluctuating soil water deficits effect WUE from the leaf to the crop level and identify if sugar beet acclimates to water deficits to increase WUE in the longer term. Two commercial sugar beet varieties with contrasting upright and prostrate canopies were examined to identify if WUE differs due to contrasting canopy architecture. The sugar beet were grown under four different irrigation regimes (fully irrigated, single drought, double drought and continually water limited) in large 610 L soil boxes in an open ended polytunnel. Measurements of leaf gas exchange, chlorophyll fluorescence and relative water content (RWC) were regularly undertaken and stomatal density, sugar and biomass yields and the associated WUE, SLW and Δ<jats:sup>13</jats:sup>C were assessed. The results showed that water deficits generally increase intrinsic (WUE<jats:sub>i</jats:sub>) and dry matter (WUE<jats:sub>DM</jats:sub>) water use efficiency but reduce yield. Sugar beet recovered fully after severe water deficits, as assessed by leaf gas exchange and chlorophyll fluorescence parameters and, except for reducing canopy size, showed no other acclimation to drought, and therefore no changes in WUE or drought avoidance. Spot measurements of WUE<jats:sub>i,</jats:sub> showed no differences between the two varieties but the prostrate variety showed lower Δ<jats:sup>13</jats:sup>C values, and traits associated with more water conservative phenotypes of a lower stomatal density and greater leaf RWC. Leaf chlorophyll content was affected by water deficit but the relationship with WUE was unclear. The difference in Δ<jats:sup>13</jats:sup>C values between the two varieties suggests traits associated with greater WUE<jats:sub>i</jats:sub> may be linked to canopy architecture.</jats:p>

<jats:p>Rice kernel quality has vital commercial value. Grain chalkiness deteriorates rice’s appearance and palatability. However, the molecular mechanisms that govern grain chalkiness remain unclear and may be regulated by many factors. In this study, we identified a stable hereditary mutant, <jats:italic>white belly grain 1</jats:italic> (<jats:italic>wbg1</jats:italic>), which has a white belly in its mature grains. The grain filling rate of <jats:italic>wbg1</jats:italic> was lower than that of the wild type across the whole filling period, and the starch granules in the chalky part were oval or round and loosely arranged. Map-based cloning showed that <jats:italic>wbg1</jats:italic> was an allelic mutant of <jats:italic>FLO10</jats:italic>, which encodes a mitochondrion-targeted P-type pentatricopeptide repeat protein. Amino acid sequence analysis found that two PPR motifs present in the C-terminal of WBG1 were lost in wbg1. This deletion reduced the splicing efficiency of <jats:italic>nad1</jats:italic> intron 1 to approximately 50% in <jats:italic>wbg1</jats:italic>, thereby partially reducing the activity of complex I and affecting ATP production in <jats:italic>wbg1</jats:italic> grains. Furthermore, haplotype analysis showed that <jats:italic>WBG1</jats:italic> was associated with grain width between <jats:italic>indica</jats:italic> and <jats:italic>japonica</jats:italic> rice varieties. These results suggested that <jats:italic>WBG1</jats:italic> influences rice grain chalkiness and grain width by regulating the splicing efficiency of <jats:italic>nad1</jats:italic> intron 1. This deepens understanding of the molecular mechanisms governing rice grain quality and provides theoretical support for molecular breeding to improve rice quality.</jats:p>

<jats:p>As a result of climate change, climatic extremes are expected to increase. For high-value crops like vegetables, irrigation is a potentially economically viable adaptation measure in western Europe. To optimally schedule irrigation, decision support systems based on crop models like AquaCrop are increasingly used by farmers. High value vegetable crops like cauliflower or spinach are grown in two distinct growth cycles per year and, additionally, have a high turnover rate of new varieties. To successfully deploy the AquaCrop model in a decision support system, it requires a robust calibration. However, it is not known whether parameters can be conserved over both growth periods, nor whether a cultivar dependent model calibration is always required. Furthermore, when data are collected from farmers’ fields, there are constraints in data availability and uncertainty. We collected data from commercial cauliflower and spinach fields in Belgium in 2019, 2020 and 2021 during different growing periods and of different cultivars. With the use of a Bayesian calibration, we confirmed the need for a condition or cultivar specific calibration for cauliflower, while for spinach, splitting the data per cultivar or pooling the data together did not improve uncertainty on the model simulations. However, due to uncertainties arising from field specific soil and weather conditions, or measurement errors from calibration data, real time field specific adjustments are advised to simulations when using AquaCrop as decision support tool. Remotely sensed or <jats:italic>in situ</jats:italic> ground data may be invaluable information to reduce uncertainty on model simulations.</jats:p>

<jats:p>Geminiviruses are known to infect several fields and horticultural crops around the globe. Grapevine geminivirus A (GGVA) was reported in the United States in 2017, and since then, it has been reported in several countries. The complete genome recovered through high-throughput sequencing (HTS)-based virome analysis in Indian grapevine cultivars had all of the six open reading frames (ORFs) and a conserved nonanucleotide sequence 5′-TAATATTAC-3′ similar to all other geminiviruses. Recombinase polymerase amplification (RPA), an isothermal amplification technique, was developed for the detection of GGVA in grapevine samples employing crude sap lysed in 0.5 M NaOH solution and compared with purified DNA/cDNA as a template. One of the key advantages of this assay is that it does not require any purification or isolation of the viral DNA and can be performed in a wide range of temperatures (18°C–46°C) and periods (10–40 min), which makes it a rapid and cost-effective method for the detection of GGVA in grapevine. The developed assay has a sensitivity up to 0.1 fg μl<jats:sup>-1</jats:sup> using crude plant sap as a template and detected GGVA in several grapevine cultivars of a major grapevine-growing area. Because of its simplicity and rapidity, it can be replicated for other DNA viruses infecting grapevine and will be a very useful technique for certification and surveillance in different grapevine-growing regions of the country.</jats:p>

<jats:sec><jats:title>Introduction</jats:title><jats:p>Multi-walled nanotubes (MWCNTs) consist of multiple rolled layers of graphene. Nitrogen plays an important role in apple growth. The effect of MWCNTs on nitrogen utilization in apple needs to be further investigated.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>In this study, the woody plant <jats:italic>Malus hupehensis</jats:italic> seedlings were used as plant materials, the distribution of MWCNTs in the roots was observed, and the effects of MWCNTs on the accumulation, distribution, and assimilation of nitrate by the seedlings were explored.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The results showed that MWCNTs could penetrate the roots of <jats:italic>Malus hupehensis</jats:italic> seedlings, and the 50, 100, and 200 µg·mL<jats:sup>-1</jats:sup> MWCNTs significantly promoted the root growth of seedlings, increased root number, root activity, fresh weight, and nitrate content of seedlings, and also increased nitrate reductase activity, free amino acid, and soluble protein content of roots and leaves. <jats:sup>15</jats:sup>N tracer experiments indicated that MWCNTs decreased the distribution ratio of <jats:sup>15</jats:sup>N-KNO<jats:sub>3</jats:sub> in <jats:italic>Malus hupehensis</jats:italic> roots but increased its distribution ratio in stems and leaves. MWCNTs improved the utilization ratio of <jats:sup>15</jats:sup>N-KNO<jats:sub>3</jats:sub> in <jats:italic>Malus hupehensis</jats:italic> seedlings, with the values being increased by 16.19%, 53.04%, and 86.44% following the 50, 100, and 200 µg·mL<jats:sup>-1</jats:sup> MWCNTs, respectively. The RT-qPCR analysis showed that MWCNTs significantly affected the expression of genes (<jats:italic>MhNRTs</jats:italic>) related to nitrate uptake and transport in roots and leaves, and <jats:italic>MhNRT1.4</jats:italic>, <jats:italic>MhNRT1.7</jats:italic>, <jats:italic>MhNRT1.8</jats:italic>, <jats:italic>MhNRT2.1</jats:italic>, <jats:italic>MhNRT2.5</jats:italic>, and <jats:italic>MhNRT2.7</jats:italic> were notably up-regulated in response to 200 µg·mL<jats:sup>-1</jats:sup> MWCNTs. Raman analysis and transmission electron microscopy images indicated that MWCNTs could enter the root tissue of <jats:italic>Malus hupehensis</jats:italic> and were distributed between the cell wall and cytoplasmic membrane. Pearson correlation analysis showed that root tip number, root fractal dimension, and root activity were the main factors affecting root uptake and assimilation of nitrate.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>These findings suggest that MWCNTs promoted root growth by entering the root, stimulated the expression of <jats:italic>MhNRTs</jats:italic>, and increased NR activity, thereby enhancing the uptake, distribution, and assimilation of nitrate by root, and ultimately improved the utilization of <jats:sup>15</jats:sup>N-KNO<jats:sub>3</jats:sub> by <jats:italic>Malus hupehensis</jats:italic> seedlings.</jats:p></jats:sec>

<jats:p>As a highly valued and multiple function tree species, the leaves of <jats:italic>Cyclocarya paliurus</jats:italic> are enriched in diverse bioactive substances with healthy function. To meet the requirement for its leaf production and medical use, the land with salt stress would be a potential resource for developing <jats:italic>C. paliurus</jats:italic> plantations due to the limitation of land resources in China. The basic helix-loop-helix (bHLH) transcription factor protein family, the second largest protein family in plants, has been found to play essential roles in the response to multiple abiotic stresses, especially salt stress. However, the <jats:italic>bHLH</jats:italic> gene family in <jats:italic>C.paliurus</jats:italic> has not been investigated. In this study, 159 <jats:italic>CpbHLH</jats:italic> genes were successfully identified from the whole-genome sequence data, and were classified into 26 subfamilies. Meanwhile, the 159 members were also analyzed from the aspects of protein sequences alignment, evolution, motif prediction, promoter cis-acting elements analysis and DNA binding ability. Based on transcriptome profiling under a hydroponic experiment with four salt concentrations (0%, 0.15%, 0.3%, and 0.45% NaCl), 9 significantly up- or down-regulated genes were screened, while 3 genes associated with salt response were selected in term of the GO annotation results. Totally 12 candidate genes were selected in response to salt stress. Moreover, based on expression analysis of the 12 candidate genes sampled from a pot experiment with three salt concentrations (0%, 0.2% and 0.4% NaCl), <jats:italic>CpbHLH36/68/146</jats:italic> were further verified to be involved in the regulation of salt tolerance genes, which is also confirmed by protein interaction network analysis. This study was the first analysis of the transcription factor family at the genome-wide level of <jats:italic>C. paliurus</jats:italic>, and our findings would not only provide insight into the function of the <jats:italic>CpbHLH</jats:italic> gene family members involved in salt stress but also drive progress in genetic improvement for the salt tolerance of <jats:italic>C. paliurus</jats:italic>.</jats:p>

<jats:p>Precision irrigation technologies using sensor feedback can provide dynamic decision support to help farmers implement DI strategies. However, few studies have reported on the use of these systems for DI management. This two-year study was conducted in Bushland, Texas to investigate the performance of the geographic information (GIS) based irrigation scheduling supervisory control and data acquisition (ISSCADA) system as a tool to manage deficit irrigation scheduling for cotton (<jats:italic>Gossypim hirsutum</jats:italic> L). Two different irrigation scheduling methods automated by the ISSCADA system — (1) a plant feedback (designated C) - based on integrated crop water stress index (<jats:sub>i</jats:sub>CWSI) thresholds, and (2) a hybrid (designated H) method, created to combine soil water depletion and the <jats:sub>i</jats:sub>CWSI thresholds, were compared with a benchmark manual irrigation scheduling (M) that used weekly neutron probe readings. Each method applied irrigation at levels designed to be equivalent to 25%, 50% and 75% replenishment of soil water depletion to near field capacity (designated I<jats:sub>25</jats:sub>, I<jats:sub>50</jats:sub> and I<jats:sub>75</jats:sub>) using the pre-established thresholds stored in the ISSCADA system or the designated percent replenishment of soil water depletion to field capacity in the M method. Fully irrigated and extremely deficit irrigated plots were also established. Relative to the fully irrigated plots, deficit irrigated plots at the I<jats:sub>75</jats:sub> level for all irrigation scheduling methods-maintained seed cotton yield, while saving water. In 2021, the irrigation savings was a minimum of 20%, while in 2022, the minimum savings was 16%. Comparing the performance of deficit irrigation scheduling between the ISSCADA system and the manual method showed that crop response for all three methods were statistically similar at each irrigation level. Because the M method requires labor intensive and expensive use of the highly regulated neutron probe, the automated decision support provided by the ISSCADA system could simplify deficit irrigation management of cotton in a semi-arid region.</jats:p>