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<jats:p>Kiwifruit, a nutrient-dense fruit, has become increasingly popular with consumers in recent decades. However, kiwifruit trees are prone to stunted growth after a few years of planting, called early tree decline. In this study, melatonin (MT), pollen polysaccharide (SF), 14-hydroxyed brassinosteroid (14-HBR) were applied alone or in combination to investigate their influence on plant growth, nutrition absorption and rhizosphere bacterial abundance in kiwifruit seedlings. The results revealed that MT, SF and 14-HBR alone treatments significantly increased leaf chlorophyll content, photosynthetic capacity and activities of dismutase and catalase compared with the control. Among them, MT treatment significantly increased the dry root biomass by 35.7%, while MT+14-HBR treatment significant enhanced the dry shoot biomass by 36.9%. Furthermore, both MT and MT+14-HBR treatments markedly improved the activities of invertase, urease, protease and phosphatase in soil, as well as the abundance of Proteobacteria and Acidobacteria in rhizosphere microorganisms based on 16S rDNA sequencing. In addition, MT treatment improved the content of available K and organic matter in soil, and increased the uptake of P, K and Fe by seedlings. In summary, 14-HBR and MT combined had the best effect on promoting rhizosphere bacterial distribution, nutrient absorption and plant growth. These findings may provide valuable guidance for solving growth weakness problem in kiwifruit cultivation.</jats:p>

<jats:p>Lowland meadows represent aboveground and belowground biodiversity reservoirs in intensive agricultural areas, improving water retention and filtration, ensuring forage production, contrasting erosion and contributing to soil fertility and carbon sequestration. Besides such major ecosystem services, the presence of functionally different plant species improves forage quality, nutritional value and productivity, also limiting the establishment of weeds and alien species. Here, we tested the effectiveness of a commercial seed mixture in restoring a lowland mixed meadow in the presence or absence of inoculation with arbuscular mycorrhizal (AM) fungi and biostimulation of symbiosis development with the addition of short chain chito-oligosaccharides (CO). Plant community composition, phenology and productivity were regularly monitored alongside AM colonization in control, inoculated and CO-treated inoculated plots. Our analyses revealed that the CO treatment accelerated symbiosis development significantly increasing root colonization by AM fungi. Moreover, the combination of AM fungal inoculation and CO treatment improved plant species evenness and productivity with more balanced composition in forage species. Altogether, our study presented a successful and scalable strategy for the reintroduction of mixed meadows as valuable sources of forage biomass; demonstrated the positive impact of CO treatment on AM development in an agronomic context, extending previous observations developed under controlled laboratory conditions and leading the way to the application in sustainable agricultural practices.</jats:p>

<jats:p>As Arabidopsis flowers mature, specialized cells within the anthers undergo meiosis, leading to the production of haploid microspores that differentiate into mature pollen grains, each containing two sperm cells for double fertilization. During pollination, the pollen grains are dispersed from the anthers to the stigma for subsequent fertilization. Transcriptomic studies have identified a large number of genes expressed over the course of male reproductive development and subsequent functional characterization of some have revealed their involvement in floral meristem establishment, floral organ growth, sporogenesis, meiosis, microsporogenesis, and pollen maturation. These genes encode a plethora of proteins, ranging from transcriptional regulators to enzymes. This review will focus on the regulatory networks that control male reproductive development, starting from flower development and ending with anther dehiscence, with a focus on transcription factors and some of their notable target genes.</jats:p>

<jats:p>Under changing climatic conditions, crop plants are more adversely affected by a combination of various abiotic stresses than by a single abiotic stress. Therefore, it is essential to identify potential donors to multiple abiotic stresses for developing climate-resilient crop varieties. Hence, the present study was undertaken with 41 germplasm accessions comprising native landraces of Tamil Nadu, Prerelease lines and cultivars were screened independently for drought, salinity, and submergence at the seedling stage during Kharif and Rabi 2022–2023. Stress was imposed separately for these three abiotic stresses on 21-day-old seedlings and was maintained for 10 days. The studied genotypes showed a significant reduction in plant biomass (PB), Relative Growth Index (RGI), relative water content (RWC), leaf photosynthesis, chlorophyll fluorescence, and Chlorophyll Concentration Index (CCI) under drought followed by salinity and submergence. Stress-tolerant indices for drought, salinity, and submergence revealed significant variation for plant biomass. Furthermore, a set of 30 SSR markers linked to drought, salinity, and submergence QTLs has been used to characterize 41 rice germplasm accessions. Our analysis suggests a significantly high polymorphism, with 28 polymorphic markers having a 93.40% in 76 loci. The mean values of polymorphic information content (PIC), heterozygosity index (HI), marker index (MI), and resolving power (RP) were 0.369, 0.433, 1.140, and 2.877, respectively. Jaccard clustering grouped all the genotypes into two major and six subclusters. According to STRUCTURE analysis, all genotypes were grouped into two major clusters, which are concurrent with a very broad genetic base (<jats:italic>K</jats:italic> = 2). Statistically significant marker-trait associations for biomass were observed for five polymorphic markers, <jats:italic>viz.</jats:italic>, RM211, RM212 (drought), RM10694 (salinity), RM219, and RM21 (submergence). Similarly, significant markers for relative shoot length were observed for RM551 (drought), RM10694 (salinity), and ART5 (submergence). Notably, the genotypes Mattaikar, Varigarudan samba, Arupatham samba, and APD19002 were identified as potential donors for multiple abiotic stress tolerance. Thus, identifying the genetic potential of germplasm could be useful for enhancing stress resilience in rice.</jats:p>

<jats:p>Water stress brought about by climate change is among the major global concerns threatening food security. Rice is an important staple food which requires high water resources. Being a semi-aquatic plant, rice is particularly susceptible to drought. The aim of this work was to develop techniques directed to promote rice resilience to water deprivation stress during germination by implementing specific seed priming treatments. Five popular Italian rice varieties were subjected to priming treatments using novel, sustainable solutions, like poly-gamma-glutamic acid (γ-PGA), denatured γ-PGA (dPGA), and iron (Fe) pulsing, alone or in combination. The effect of the developed priming methods was tested under optimal conditions as well as under water deprivation stress imposed by polyethylene glycol (PEG) treatments. The priming efficacy was phenotypically determined in terms of germination behavior by measuring a series of parameters (germinability, germination index, mean germination time, seed vigor index, root and shoot length, germination stress tolerance index). Biochemical analyses were carried out to measure the levels of iron uptake and accumulation of reactive oxygen species (ROS). Integrative data analyses revealed that the rice varieties exhibited a strong genotype- and treatment-specific germination behavior. PEG strongly inhibited germination while most of the priming treatments were able to rescue it in all varieties tested except for Unico, which can be defined as highly stress sensitive. Molecular events (DNA repair, antioxidant response, iron homeostasis) associated with the transition from seed to seedling were monitored in terms of changes in gene expression profiles in two varieties sensitive to water deprivation stress with different responses to priming. The investigated genes appeared to be differentially expressed in a genotype-, priming treatment-, stress- and stage-dependent manner. The proposed seed priming treatments can be envisioned as sustainable and versatile agricultural practices that could help in addressing the impact of climate challenges on the agri-food system.</jats:p>

<jats:p>Root architecture is an important agronomic trait that plays an essential role in water uptake, soil compactions, nutrient recycling, plant–microbe interactions, and hormone-mediated signaling pathways. Recently, significant advancements have been made in understanding how the complex interactions of phytohormones regulate the dynamic organization of root architecture in crops. Moreover, phytohormones, particularly auxin, act as internal regulators of root development in soil, starting from the early organogenesis to the formation of root hair (RH) through diverse signaling mechanisms. However, a considerable gap remains in understanding the hormonal cross-talk during various developmental stages of roots. This review examines the dynamic aspects of phytohormone signaling, cross-talk mechanisms, and the activation of transcription factors (TFs) throughout various developmental stages of the root life cycle. Understanding these developmental processes, together with hormonal signaling and molecular engineering in crops, can improve our knowledge of root development under various environmental conditions.</jats:p>

<jats:sec><jats:title>Introduction</jats:title><jats:p>With current trends in global climate change, both flooding episodes and higher levels of CO<jats:sub>2</jats:sub> have been key factors to impact plant growth and stress tolerance. Very little is known about how both factors can influence the microbiome diversity and function, especially in tolerant soybean cultivars. This work aims to (i) elucidate the impact of flooding stress and increased levels of CO<jats:sub>2</jats:sub> on the plant defenses and (ii) understand the microbiome diversity during flooding stress and elevated CO<jats:sub>2</jats:sub> (eCO<jats:sub>2</jats:sub>).</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We used next-generation sequencing and bioinformatic methods to show the impact of natural flooding and eCO<jats:sub>2</jats:sub> on the microbiome architecture of soybean plants' below- (soil) and above-ground organs (root and shoot). We used high throughput rhizospheric extra-cellular enzymes and molecular analysis of plant defense-related genes to understand microbial diversity in plant responses during eCO<jats:sub>2</jats:sub> and flooding.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Results revealed that bacterial and fungal diversity was substantially higher in combined flooding and eCO<jats:sub>2</jats:sub> treatments than in non-flooding control. Microbial diversity was soil&amp;gt;root&amp;gt;shoot in response to flooding and eCO<jats:sub>2</jats:sub>. We found that sole treatment of eCO<jats:sub>2</jats:sub> and flooding had significant abundances of <jats:italic>Chitinophaga, Clostridium</jats:italic>, and <jats:italic>Bacillus</jats:italic>. Whereas the combination of flooding and eCO2 conditions showed a significant abundance of <jats:italic>Trichoderma</jats:italic> and <jats:italic>Gibberella</jats:italic>. Rhizospheric extra-cellular enzyme activities were significantly higher in eCO<jats:sub>2</jats:sub> than flooding or its combination with eCO<jats:sub>2</jats:sub>. Plant defense responses were significantly regulated by the oxidative stress enzyme activities and gene expression of <jats:italic>Elongation factor 1</jats:italic> and <jats:italic>Alcohol dehydrogenase 2</jats:italic> in floodings and eCO<jats:sub>2</jats:sub> treatments in soybean plant root or shoot parts.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>This work suggests that climatic-induced changes in eCO<jats:sub>2</jats:sub> and submergence can reshape microbiome structure and host defenses, essential in plant breeding and developing stress-tolerant crops. This work can help in identifying core-microbiome species that are unique to flooding stress environments and increasing eCO<jats:sub>2</jats:sub>.</jats:p></jats:sec>

<jats:p>The genus <jats:italic>Tetradesmus</jats:italic> (Scenedesmaceae; Sphaeropleales) comprises one of the most abundant green algae in freshwater environments. It includes morphologically diverse species that exhibit bundle-like, plane-arranged coenobia, and unicells, because several different <jats:italic>Scenedesmus</jats:italic>-like groups were integrated into this genus based on phylogenetic analysis. Nevertheless, there is no clear information regarding the phylogenetic relationship of <jats:italic>Tetradesmus</jats:italic> species, determined using several marker genes, because of low phylogenetic support and insufficient molecular data. Currently, genome information is available from diverse taxa, which could provide high-resolution evolutionary relationships. In particular, phylogenetic studies using chloroplast genomes demonstrated the potential to establish high-resolution phylogenetic relationships. However, only three chloroplast genomes are available from the genus <jats:italic>Tetradesmus</jats:italic>. In this study, we newly generated 9 chloroplast genomes from <jats:italic>Tetradesmus</jats:italic> and constructed a high-resolution phylogeny using a concatenated alignment of 69 chloroplast protein sequences. We also report one novel species (<jats:italic>T</jats:italic>. <jats:italic>lancea</jats:italic>), one novel variety (<jats:italic>T</jats:italic>. <jats:italic>obliquus</jats:italic> var. <jats:italic>spiraformis</jats:italic>), and two novel formae (<jats:italic>T</jats:italic>. <jats:italic>dissociatus</jats:italic> f. <jats:italic>oviformis</jats:italic>, <jats:italic>T</jats:italic>. <jats:italic>obliquus</jats:italic> f. <jats:italic>rectilineare</jats:italic>) within the genus <jats:italic>Tetradesmus</jats:italic> based on morphological characteristics (e.g., cellular arrangements and coenobial types) and genomic features (e.g., different exon–intron structures in chloroplast genomes). Moreover, we taxonomically reinvestigated the genus <jats:italic>Tetradesmus</jats:italic> based on these results. Altogether, our study can provide a comprehensive understanding of the taxonomic approaches for investigating this genus.</jats:p>

<jats:sec><jats:title>Introduction</jats:title><jats:p>Global climate change exerts a significant impact on the nitrogen supply and photosynthesis ability in land-based plants. The photosynthetic capacity of dominant grassland species is important if we are to understand carbon cycling under climate change. Drought stress is one of the major factors limiting plant photosynthesis, and nitrogen (N) is an essential nutrient involved in the photosynthetic activity of leaves. The regulatory mechanisms responsible for the effects of ammonium (NH<jats:sub>4</jats:sub><jats:sup>+</jats:sup>) and nitrate (NO<jats:sub>3</jats:sub><jats:sup>-</jats:sup>) on the drought-induced photoinhibition of photosystem II (PSII) in plants have yet to be fully elucidated. Therefore, there is a significant need to gain a better understanding of the role of electron transport in the photoinhibition of PSII.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>In the present study, we conducted experiments with normal watering (LD), severe drought (MD), and extreme drought (HD) treatments, along with no nitrogen (N0), ammonium (NH<jats:sub>4</jats:sub>), nitrate (NO<jats:sub>3</jats:sub>), and mixed nitrogen (NH<jats:sub>4</jats:sub>NO<jats:sub>3</jats:sub>) treatments. We analyzed pigment accumulation, reactive oxygen species (ROS) accumulation, photosynthetic enzyme activity, photosystem activity, electron transport, and O-J-I-P kinetics.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Analysis showed that increased nitrate application significantly increased the leaf chlorophyll content per unit area (Chl<jats:sub>area</jats:sub>) and nitrogen content per unit area (N<jats:sub>area</jats:sub>) (p&amp;lt; 0.05). Under HD treatment, ROS levels were lower in NO<jats:sub>3</jats:sub>-treated plants than in N0 plants, and there was no significant difference in photosynthetic enzyme activity between plants treated with NO<jats:sub>3</jats:sub> and NH<jats:sub>4</jats:sub>NO<jats:sub>3</jats:sub>. Under drought stress, the maximum photochemical efficiency of PSII (Fv/Fm), PSII electron transport rate (ETR), and effective quantum yield of PSII (φPSII) were significant higher in NO<jats:sub>3</jats:sub>-treated plants (p&amp;lt; 0.05). Importantly, the K-band and G-band were higher in NO<jats:sub>3</jats:sub>-treated plants.</jats:p></jats:sec><jats:sec><jats:title>Discussion</jats:title><jats:p>These results suggest that drought stress hindered the formation of NADPH and ATP in N0 and NH<jats:sub>4</jats:sub>-treated <jats:italic>L. chinensis</jats:italic> plants, thus damaging the donor side of the PSII oxygen-evolving complex (OEC). After applying nitrate, higher photosynthetic enzyme and antioxidant enzyme activity not only protected PSII from photodamage under drought stress but also reduced the rate of damage in PSII during the growth of <jats:italic>L. chinensis</jats:italic> growth under drought stress.</jats:p></jats:sec>