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An efficient and simple procedure was systematically developed for inducing direct somatic embryogenesis and plantlet regeneration from leaf sheath explants of Curcuma amada Roxb. A two-step culture system was used to induce somatic embryogenesis. The optimized procedure resulted in direct somatic embryogenesis from 93.3% explants after 3-wk culture. Leaf sheath explants were incubated for 2 wk on medium containing 2.24 μM 2,4-dichlorophenoxyacetic acid and 1.11 μM 6-benzyladenine to initiate direct somatic embryogenesis. Thereafter, these explants were transferred to a medium containing 9.10 μM thidiazuron and 1.33 μM α-naphthaleneacetic acid. Elongated somatic embryos obtained from these cultures germinated readily, and the optimal frequency of plantlet development (86.7%) was achieved when embryos were cultured in darkness on 1/2 strength Murashige and Skoog medium containing 1.44 μM gibberellic acid. Histological and scanning electron microscopic studies showed that the initial cell divisions that led to embryo formation occurred in epidermal and subepidermal cells, followed by the development of globular and elongated structures that appeared to be somatic embryos. The presence of a clear protoderm in the globular structures and procambial strands in the elongated structures confirmed that these structures were true somatic embryos. Plantlets derived from somatic embryos were acclimatized successfully to ex vitro conditions at a survival rate of 87.43% and developed with normal phenotypes.

Paspalum dilatatum occupies different topographic positions in the Flooding Pampa, Argentina. Populations from different positions are subjected to various regimes of flooding and drought, both of which may occur in the same growing season. We investigated the constitutive and plastic anatomical traits of P. dilatatum populations from habitats with contrasting regimes of flooding and drought. Both events affected root and sheath anatomy, and these effects were similar for clones from different topographic positions. Flooding increased the aerenchymatous tissue in the root cortex and the leaf sheaths and decreased the number of root hairs per unit of root length. Drought decreased the diameter of root metaxylem vessels, thus lowering the risk of embolisms and increasing water-flow resistance, and increased the number of root hairs, thereby increasing water uptake ability. In addition to these plastic responses, all clones showed constitutive characteristics that may confer an ability to withstand sudden events of flooding or drought: a high proportion of aerenchyma, which may maintain aeration before plastic responses take place; sclerenchyma, which may prevent root and leaf sheath collapse by soil compaction; and a conspicuous endodermis, which may protect stelar tissues from desiccation. Both constitutive and plastic anatomical characteristics are likely to contribute to the ability of this species to occupy widely different topographic positions and to resist temporal variations in water and oxygen availability.

Brassinosteroid (BR) and gibberellin (GA) are two predominant hormones regulating plant cell elongation. A defect in either of these leads to reduced plant growth and dwarfism. However, their relationship remains unknown in rice (Oryza sativa). Here, we demonstrated that BR regulates cell elongation by modulating GA metabolism in rice. Under physiological conditions, BR promotes GA accumulation by regulating the expression of GA metabolic genes to stimulate cell elongation. BR greatly induces the expression of D18/GA3ox-2, one of the GA biosynthetic genes, leading to increased GA₁ levels, the bioactive GA in rice seedlings. Consequently, both d18 and loss-of-function GA-signaling mutants have decreased BR sensitivity. When excessive active BR is applied, the hormone mostly induces GA inactivation through upregulation of the GA inactivation gene GA2ox-3 and also represses BR biosynthesis, resulting in decreased hormone levels and growth inhibition. As a feedback mechanism, GA extensively inhibits BR biosynthesis and the BR response. GA treatment decreases the enlarged leaf angles in plants with enhanced BR biosynthesis or signaling. Our results revealed a previously unknown mechanism underlying BR and GA crosstalk depending on tissues and hormone levels, which greatly advances our understanding of hormone actions in crop plants and appears much different from that in Arabidopsis thaliana.

Leaf sheaths of rattans are long, tubular and persistent and unlike many self-supporting palms, extend far from the apex of the plant. The mechanical role of the leaf sheath was investigated in eight rattan species of the subfamily Calamoideae. The main objective was to analyse its influence on the mechanical architecture and contribution to the climbing habit. Bending mechanical properties were measured along climbing axes before and after removal of leaf sheaths. Results were related to stem and leaf sheath geometry and mechanical properties. Contribution of the leaf sheath to axial flexural rigidity was high (c. 90%) in the early stages of growth and towards the apex of older climbing axes for all climbing palms tested. Senescence and loss of the leaf sheath strongly influenced axial stiffness. A nonclimbing species, Calamus erectus, showed a different mechanical architecture. Although lacking secondary growth, palms have been able to develop successful climbers with a mechanical architecture broadly analogous to, although developmentally different from, dicotyledonous lianas. The role of the leaf sheath in modulating mechanical properties during ontogeny ought not to be neglected in studies on monocotyledons, as it possibly contributed significantly to the ways in which different growth forms have evolved in the group.

This study investigates the enhancement of mechanical characteristics of hybrid polymer composites reinforced with palmyra palm leaflet (PPL) and coconut sheath leaf (CSL) fibers by integrating tamarind shell powder as a filler material. The composites were fabricated with varying ratios of PPL and CSL fibers, and their tensile strength, flexural strength, interlaminar shear strength (ILSS), impact strength, hardness, and water absorption were evaluated. The composite with 20% PPL and 10% CSL exhibited superior mechanical performance, achieving the highest tensile strength of 42 MPa, flexural strength of 94 MPa, ILSS of 7.52 MPa, and impact strength of 5.98 J. Hardness values peaked at 84 SD for the same composition. Moreover, the integration of tamarind shell powder significantly improved the mechanical properties compared to composites without filler, which showed lower values across all parameters. Water absorption tests revealed an increase in water uptake with filler incorporation, though within acceptable limits for practical applications. Scanning electron microscopy supported these results by revealing enhanced fiber-matrix bonding and better dispersion of the filler, resulting in fewer voids and defects. This research highlights the potential of bio-based fillers in optimizing the mechanical performance of hybrid composites for sustainable engineering applications.

OsWRKY76 encodes a group IIa WRKY transcription factor of rice. The expression of OsWRKY76 was induced within 48h after inoculation with rice blast fungus (Magnaporthe oryzae), and by wounding, low temperature, benzothiadiazole, and abscisic acid. Green fluorescent protein-fused OsWRKY76 localized to the nuclei in rice epidermal cells. OsWRKY76 showed sequence-specific DNA binding to the W-box element in vitro and exhibited W-box-mediated transcriptional repressor activity in cultured rice cells. Overexpression of OsWRKY76 in rice plants resulted in drastically increased susceptibility to M. oryzae, but improved tolerance to cold stress. Microarray analysis revealed that overexpression of OsWRKY76 suppresses the induction of a specific set of PR genes and of genes involved in phytoalexin synthesis after inoculation with blast fungus, consistent with the observation that the levels of phytoalexins in the transgenic rice plants remained significantly lower than those in non-transformed control plants. Furthermore, overexpression of OsWRKY76 led to the increased expression of abiotic stress-associated genes such as peroxidase and lipid metabolism genes. These results strongly suggest that OsWRKY76 plays dual and opposing roles in blast disease resistance and cold tolerance.

The AP2/ERF family is a large group of plant-specific transcription factors that play an important role in many biological processes, such as growth, development, and abiotic stress responses. OsDREB2B, a dehydration responsive factor (DRE/CRT) in the DREB subgroup of the AP2/ERF family, is associated with abiotic stress responses, such as cold, drought, salt, and heat stress, in Arabidopsis or rice. However, its role in regulating plant growth and development in rice is unclear. In this study, we reported a new function of OsDREB2B, which negatively regulates plant height in rice. Compared with wild type (WT), OsDREB2B- overexpressing (OE) rice exhibited dwarf phenotypes, such as reduction in plant height, internode length, and seed length, as well as grain yield, while the knockout mutants developed by CRISPR/Cas9 technology exhibited similar phenotypes. Spatial expression analysis revealed that OsDREB2B was highly expressed in the leaf sheaths. Under exogenous GA 3 application, OsDREB2B expression was induced, and the length of the second leaf sheath of the OsDREB2B- OE lines recovered to that of the WT. OsDREB2B localized to the nucleus of the rice protoplast acted as a transcription activator and upregulated OsAP2-39 by directly binding to its promoter. OsDREB2B- OE lines reduced endogenous bioactive GA levels by downregulating seven GA biosynthesis genes and upregulating eight GA deactivation genes but not GA signaling genes. The yeast two-hybrid assay and bimolecular fluorescence complementation assay showed that OsDREB2B interacted with OsWRKY21. In summary, our study suggests that OsDREB2B plays a negative role in rice growth and development by regulating GA metabolic gene expression, which is mediated by OsAP2-39 and OsWRKY21, thereby reducing GA content and rice plant height.

Seagrass is constantly challenged with transporting sufficient O₂from above‐ to belowground tissue via aerenchyma in order to maintain aerobic metabolism and provide protection against phytotoxins. Electrochemical microsensors were used in combination with a custom‐made experimental chamber to analyse the belowground biogeochemical microenvironment of Zostera muelleri under changing environmental conditions. Measurements revealed high radial O₂release of up to 500 nmol O₂ cm⁻² h⁻¹from the base of the leaf sheath, maintaining a c. 300‐μm‐wide plant‐mediated oxic microzone and thus protecting the vital meristematic regions of the rhizome from reduced phytotoxic metabolites such as hydrogen sulphide (H₂S). H₂S intrusion was prevented through passive diffusion of O₂to belowground tissue from leaf photosynthesis in light, as well as from the surrounding water column into the flow‐exposed plant parts during darkness. Under water column hypoxia, high belowground H₂S concentrations at the tissue surface correlated with the inability to sustain the protecting oxic microshield around the meristematic regions of the rhizome. We also found increased pH levels in the immediate rhizosphere of Z. muelleri, which may contribute to further detoxification of H₂S through shifts in the chemical speciation of sulphide. Zostera muelleri can modify the geochemical conditions in its immediate rhizosphere, thereby reducing its exposure to H₂S.

The present study deals with the fabrication of epoxy composites reinforced with 50 wt% of date palm leaf sheath (G), palm tree trunk (L), fruit bunch stalk (AA), and leaf stalk (A) as filler by the hand lay-up technique. The developed composites were characterized and compared in terms of mechanical, physical and morphological properties. Mechanical tests revealed that the addition of AA improves tensile (20.60–40.12 MPa), impact strength (45.71–99.45 J/m), flexural strength (32.11–110.16 MPa) and density (1.13–1.90 g/cm3). The water absorption and thickness swelling values observed in this study were higher for AA/epoxy composite, revealing its higher cellulosic content, compared to the other composite materials. The examination of fiber pull-out, matrix cracks, and fiber dislocations in the microstructure and fractured surface morphology of the developed materials confirmed the trends for mechanical properties. Overall, from results analysis it can be concluded that reinforcing epoxy matrix with AA filler effectively improves the properties of the developed composite materials. Thus, date palm fruit bunch stalk filler might be considered as a sustainable and green promising reinforcing material similarly to other natural fibers and can be used for diverse commercial, structural, and nonstructural applications requiring high mechanical resistance.

Panicle blast 1 (Pb1) is a panicle blast resistance gene derived from the indica rice cultivar “Modan.” Pb1 encodes a coiled-coil–nucleotide-binding site–leucine-rich repeat (CC-NB-LRR) protein and confers durable, broad-spectrum resistance to Magnaporthe oryzae races. Here, we investigated the molecular mechanisms underlying Pb1 -mediated blast resistance. The Pb1 protein interacted with WRKY45, a transcription factor involved in induced resistance via the salicylic acid signaling pathway that is regulated by the ubiquitin proteasome system. Pb1 -mediated panicle blast resistance was largely compromised when WRKY45 was knocked down in a Pb1 -containing rice cultivar. Leaf-blast resistance by Pb1 overexpression (Pb1 -ox) was also compromised in WRKY45 knockdown /Pb1 -ox rice. Blast infection induced higher accumulation of WRKY45 in Pb1 -ox than in control Nipponbare rice. Overexpression of Pb1-Quad , a coiled-coil domain mutant that had weak interaction with WRKY45, resulted in significantly weaker blast resistance than that of wild-type Pb1 . Overexpression of Pb1 with a nuclear export sequence failed to confer blast resistance to rice. These results suggest that the blast resistance of Pb1 depends on its interaction with WRKY45 in the nucleus. In a transient system using rice protoplasts, coexpression of Pb1 enhanced WRKY45 accumulation and increased WRKY45-dependent transactivation activity, suggesting that protection of WRKY45 from ubiquitin proteasome system degradation is possibly involved in Pb1-dependent blast resistance.