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<jats:sec><jats:title>Introduction</jats:title><jats:p>In natural systems, diverse plant communities tend to prevent a single species from dominating. Similarly, management of invasive alien plants may be achieved through various combinations of competing species.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We used a de Wit replacement series to compare different combinations of sweet potato (<jats:italic>Ipomoea batatas</jats:italic> (L.) Lam), hyacinth bean (<jats:italic>Lablab purpureus</jats:italic> (L.) Sweet) and mile-a-minute (<jats:italic>Mikania micrantha</jats:italic> Kunth) through measures of photosynthesis, plant growth, nutrient levels in plant tissue and soil, and competitive ability.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Cultured alone sweet potato and hyacinth beans exhibited higher total biomass, leafstalk length, and leaf area than mile-a-minute. In mixed culture, either sweet potato or hyacinth bean or both together significantly suppressed the mile-a-minute parameters, i.e., plant height, branch, leaf, adventitious root, and biomass (P&amp;lt;0.05). Based on a significantly lower than 1.0 relative yield of the three plant species in mixed culture, we showed intraspecific competition to be less than interspecific competition. Calculated indices (relative yield, relative yield total, competitive balance index, and change in contribution) demonstrated a higher competitive ability and higher influence of either crop compared to mile-a-minute. The presence of sweet potato and hyacinth bean, especially with both species in combination, significantly reduced (P&amp;lt;0.05) mile-a-minute’s net photosynthetic rate (Pn), antioxidant enzyme activities (superoxide dismutase, peroxidase, catalase, and malondialdehyde), chlorophyll content, and nutrient content (N, P, and K). In soil with mile-a-minute in monoculture soil organic matter, total and available N, total and available K, and available P were significantly greater (P&amp;lt;0.05) than in soil with sweet potato grown in monoculture, but less than in soil with hyacinth bean grown in monoculture soil. Nutrient soil content was comparatively reduced for plant mixtures. Plant height, leaf, biomass, Pn, antioxidant enzyme activities, and plant and soil nutrient contents of sweet potato and hyacinth bean tended to be much greater when grown with two crops compared to in mixture with just sweet potato or hyacinth bean.</jats:p></jats:sec><jats:sec><jats:title>Discussion</jats:title><jats:p>Our results suggest that the competitive abilities of both sweet potato and hyacinth bean were greater than that of mile-a-minute, and also that mile-a-minute suppression was significantly improved via a combination of the two crops compared to either sweet potato or hyacinth bean alone.</jats:p></jats:sec>

<jats:p>The <jats:italic>Brassica napus</jats:italic> (<jats:italic>B. napus</jats:italic>) <jats:italic>LOR</jats:italic> (<jats:italic>Lurp-One-Related</jats:italic>) gene family is a little-known gene family characterized by a conserved LOR domain in the proteins. Limited research in <jats:italic>Arabidopsis</jats:italic> showed that <jats:italic>LOR</jats:italic> family members played important roles in <jats:italic>Hyaloperonospora parasitica</jats:italic> (<jats:italic>Hpa</jats:italic>) defense. Nevertheless, there is a paucity of research investigating the role of the <jats:italic>LOR</jats:italic> gene family towards their responses to abiotic stresses and hormone treatments. This study encompassed a comprehensive survey of 56 <jats:italic>LOR</jats:italic> genes in <jats:italic>B. napus</jats:italic>, which is a prominent oilseed crop that holds substantial economic significance in China, Europe, and North America. Additionally, the study evaluated the expression profiles of these genes in response to salinity and ABA stress. Phylogenetic analysis showed that 56 <jats:italic>BnLORs</jats:italic> could be divided into 3 subgroups (8 clades) with uneven distribution on 19 chromosomes. 37 out of 56 <jats:italic>BnLOR</jats:italic> members have experienced segmental duplication and 5 of them have undergone tandem repeats events with strong evidence of purifying selection. Cis-regulatory elements (CREs) analysis indicated that <jats:italic>BnLORs</jats:italic> involved in process such as light response, hormone response, low temperature response, heat stress response, and dehydration response. The expression pattern of <jats:italic>BnLOR</jats:italic> family members revealed tissue specificity. RNA-Seq and qRT-PCR were used to validate <jats:italic>BnLOR</jats:italic> gene expression under temperature, salinity and ABA stress, revealing that most <jats:italic>BnLORs</jats:italic> showed inducibility. This study enhanced our comprehension of the <jats:italic>B. napus LOR</jats:italic> gene family and could provide valuable information for identifying and selecting genes for stress resistant breeding.</jats:p>

<jats:p><jats:italic>Mentha canadensis</jats:italic> L. is an important spice crop and medicinal herb with high economic value. The plant is covered with peltate glandular trichomes, which are responsible for the biosynthesis and secretion of volatile oils. Plant non-specific lipid transfer proteins (nsLTPs) belong to a complex multigenic family involved in various plant physiological processes. Here, we cloned and identified a non-specific lipid transfer protein gene (<jats:italic>McLTPII.9</jats:italic>) from <jats:italic>M. canadensis</jats:italic>, which may positively regulate peltate glandular trichome density and monoterpene metabolism. <jats:italic>McLTPII.9</jats:italic> was expressed in most <jats:italic>M. canadensis</jats:italic> tissues. The GUS signal driven by the <jats:italic>McLTPII.9</jats:italic> promoter in transgenic <jats:italic>Nicotiana tabacum</jats:italic> was observed in stems, leaves, and roots; it was also expressed in trichomes. <jats:italic>McLTPII.9</jats:italic> was associated with the plasma membrane. Overexpression of <jats:italic>McLTPII.9</jats:italic> in peppermint (<jats:italic>Mentha piperita.</jats:italic> L) significantly increased the peltate glandular trichome density and total volatile compound content compared with wild-type peppermint; it also altered the volatile oil composition. In <jats:italic>McLTPII.9</jats:italic>-overexpressing (OE) peppermint, the expression levels of several monoterpenoid synthase genes and glandular trichome development-related transcription factors—such as limonene synthase (<jats:italic>LS</jats:italic>), limonene-3-hydroxylase (<jats:italic>L3OH</jats:italic>), geranyl diphosphate synthase (<jats:italic>GPPS</jats:italic>), <jats:italic>HD-ZIP3</jats:italic>, and <jats:italic>MIXTA</jats:italic>—exhibited varying degrees of alteration. <jats:italic>McLTPII.9</jats:italic> overexpression resulted in both a change in expression of genes for terpenoid biosynthetic pathways which corresponded with an altered terpenoid profile in OE plants. In addition, peltate glandular trichome density was altered in the OE plants as well as the expression of genes for transcription factors that were shown to be involved in trichome development in plants.</jats:p>

<jats:sec><jats:title>Introduction</jats:title><jats:p>The case of combined drought and salinity stress is increasingly becoming a constraint to rice production, especially in coastal areas and river deltas where low rainfall not only reduces soil moisture levels but also reduces the flow of river water, resulting in intrusion of saline sea-water. A standardized screening method is needed in order to systematically evaluate rice cultivars under combined drought+salinity at the same time because sequential stress of salinity followed by drought or vice-versa is not similar to simultaneous stress effects. Therefore, we aimed to develop a screening protocol for combined drought+salinity stress applied to soil-grown plants at seedling stage.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>The study system used 30-L soil-filled boxes, which allowed a comparison of plant growth under control conditions, individual drought and salinity stress, as well as combined drought+salinity. A set of salinity tolerant and drought tolerant cultivars were tested, together with several popular but salinity and drought-susceptible varieties that are grown in regions prone to combined drought+salinity. A range of treatments were tested including different timings of the drought and salinity application, and different severities of stress, in order to determine the most effective that resulted in visible distinction among cultivars. The challenges related to determining a protocol with repeatable seedling stage stress treatment effects while achieving a uniform plant stand are described here.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The optimized protocol simultaneously applied both stresses by planting into saline soil at 75% of field capacity which was then allowed to undergo progressive drydown. Meanwhile, physiological characterization revealed that chlorophyll fluorescence at seedling stage correlated well with grain yield when drought stress was applied to vegetative stage only.</jats:p></jats:sec><jats:sec><jats:title>Discussion</jats:title><jats:p>The drought+salinity protocol developed here can be used for screening rice breeding populations as part of a pipeline to develop new rice varieties with improved adaptation to combined stresses.</jats:p></jats:sec>

<jats:p>Flowers are critical for successful reproduction and have been a major axis of diversification among angiosperms. As the frequency and severity of droughts are increasing globally, maintaining water balance of flowers is crucial for food security and other ecosystem services that rely on flowering. Yet remarkably little is known about the hydraulic strategies of flowers. We characterized hydraulic strategies of leaves and flowers of ten species by combining anatomical observations using light and scanning electron microscopy with measurements of hydraulic physiology (minimum diffusive conductance (<jats:italic>g</jats:italic><jats:sub>min</jats:sub>) and pressure-volume (PV) curves parameters). We predicted that flowers would exhibit higher <jats:italic>g</jats:italic><jats:sub>min</jats:sub> and higher hydraulic capacitance than leaves, which would be associated with differences in intervessel pit traits because of their different hydraulic strategies. We found that, compared to leaves, flowers exhibited: 1) higher <jats:italic>g</jats:italic><jats:sub>min</jats:sub>, which was associated with higher hydraulic capacitance (<jats:italic>C</jats:italic><jats:sub>T</jats:sub>); 2) lower variation in intervessel pit traits and differences in pit membrane area and pit aperture shape; and 3) independent coordination between intervessel pit traits and other anatomical and physiological traits; 4) independent evolution of most traits in flowers and leaves, resulting in 5) large differences in the regions of multivariate trait space occupied by flowers and leaves. Furthermore, across organs intervessel pit trait variation was orthogonal to variation in other anatomical and physiological traits, suggesting that pit traits represent an independent axis of variation that have as yet been unquantified in flowers. These results suggest that flowers, employ a drought-avoidant strategy of maintaining high capacitance that compensates for their higher <jats:italic>g</jats:italic><jats:sub>min</jats:sub> to prevent excessive declines in water potentials. This drought-avoidant strategy may have relaxed selection on intervessel pit traits and allowed them to vary independently from other anatomical and physiological traits. Furthermore, the independent evolution of floral and foliar anatomical and physiological traits highlights their modular development despite being borne from the same apical meristem.</jats:p>

<jats:p>Citrus plants are sensitive to waterlogging, which can cause yield reduction. Their production heavily depends on the rootstock being used for grafting of scion cultivars, and the rootstock is the first organ to be affected by waterlogging stress. However, the underlying molecular mechanisms of waterlogging stress tolerance remain elusive. In this study we investigated the stress response of two waterlogging-tolerant citrus varieties (<jats:italic>Citrus junos</jats:italic> Sieb ex Tanaka cv. Pujiang Xiangcheng and Ziyang Xiangcheng), and one waterlogging-sensitive variety (red tangerine) at the morphological, physiological, and genetic levels in leaf and root tissues of partially submerged plants. The results showed that waterlogging stress significantly decreased the SPAD value and root length but did not obviously affect the stem length and new root numbers. The malondialdehyde (MDA) content and the enzyme activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), and catalase (CAT) were enhanced in the roots. The RNA-seq analysis revealed that the differentially expressed genes (DEGs) were mainly linked to ‘cutin, suberine, and wax biosynthesis’, ‘diterpenoid biosynthesis’, and ‘glycerophospholipid metabolism’ in the leaves, whereas were linked to ‘flavonoid biosynthesis’, ‘biosynthesis of secondary metabolites and metabolic pathways’ in the roots. Finally, we developed a working model based on our results to elucidate the molecular basis of waterlogging-responsive in citrus. Therefore, our data obtained in this study provided valuable genetic resources that will facilitate the breeding of citrus varieties with improved waterlogging tolerance.</jats:p>