Explore the vast range of titles available.

In rice, internode elongation is a critical aspect of plant development and agricultural productivity. Previous morphological and histochemical studies using [ 3 H]thymidine have visualized the cell division zone (intercalary meristem) in internodes. However, it has remained unclear how the intercalary meristem forms during stem development. In addition, while a pith cavity forms in the central part of the rice stem, the spatiotemporal relationship between pith cavity formation and intercalary meristem development is not well understood. Therefore, we performed histological analysis of intercalary meristem and pith cavity development using C9285, a deepwater rice variety that shows internode elongation from the vegetative growth stage. We classified the developmental stages of the stem into four stages based on the analysis of pith cavity formation using Trypan blue, Calcein-AM, and MitoRed staining, and visualized dividing cells using the Click-iT EdU imaging assay. In Stage 1, no pith cavity was formed. Vertical cell rows were observed between above the axillary bud attachment and the upper node, suggesting anticlinal divisions that lead to internode formation in the early stage of stem development. In Stage 2, the first pith cavity formed in the pith of the foot, which is the region of axillary bud attachment. Compared to cell division in the internode, that in the foot was significantly activated resulting in slight elongation from Stage 1 to Stage 2. In Stage 3, cell division in the foot ceased, while active cell division at the base of the internode led to significant vertical elongation. The second pith cavity formed due to cell death in the pith of the internode. In Stage 4, the two pith cavities connected to form a single large pith cavity. Although the intercalary meristem maintained cell division activity, the number of cell divisions decreased. Based on these results, we propose a model for stem development that involves two phases of elongation regulation: primary elongation involving slight elongation in the foot, and secondary elongation involving significant internode elongation due to the activation of cell division and cell elongation in the intercalary meristem. This is the first study to anatomically elucidate the spatiotemporal relationship between intercalary meristem development and pith cavity formation in rice stem development. It provides new insights for future research on rice stem development and studies of other grass species.

Summary Pith cavity formation is critical for bamboo to overcome the bending force during its fast growth; however, the underlying molecular mechanisms remain largely unknown. Multiple approaches, including anatomical dissection, mathematical modelling and transcriptome profiling, were employed in this study to investigate the biology of pith cavity formation in bamboo Pseudosasa japonica. We found that the corruption of pith tissue occurred sequentially and asymmetrically from the top‐centre of the internode down to the bottom, which might be caused by the combined effects of asymmetrical radial and axial tensile forces during shoot‐wall cell elongation and spiral growth of bamboo internodes. Programmed cell death (PCD) in pitch manifested by TUNEL positive nuclei, DNA cleavage and degraded organelles, and potentially regulated by ethylene and calcium signalling pathway, ROS burst, cell wall modification, proteolysis and nutrient recycle genes, might be responsible for pith tissue corruption of Ps. japonica. Although similar physiological changes and transcriptome profiles were found in different bamboo species, different formation rates of pith cavity were observed, which might be caused by different pith cells across the internode that were negatively correlated with the culm diameter. These findings provided a systematical view on the formation of bamboo pith cavity and revealed that PCD plays an important role in the bamboo pith cavity formation.

Submergence, a major abiotic stress in hydrologically dynamic ecosystems, poses severe challenges to plant survival and growth. Existing studies have demonstrated that plants employ a suite of adaptive strategies to tolerate submergence. These divergent adaptive responses are endogenously regulated by phytohormones; yet, the underlying mechanisms that connect hormonal regulation, anatomical plasticity, and growth adaptation in the context of submergence remain insufficiently elucidated. Alternanthera philoxeroides (Mart.) Griseb. is widely distributed in disturbed, flood-prone habitats and exhibits exceptional adaptability to hydrological fluctuations, making it a suitable species for exploring submergence stress responses. This study investigated A. philoxeroides’ responses to three hydrological conditions (non-submergence, partial submergence, complete submergence), focusing on stem growth and its anatomical and hormonal regulatory drivers. Results revealed an unexpected growth pattern: complete submergence induced significantly faster stem elongation than partial submergence, with this growth-promoting effect most pronounced in immature stems—particularly the basal parts of immature internodes. This elongation correlated positively with enlarged pith cavities and elevated gibberellin (GA 4 ), while it was significantly negatively correlated with abscisic acid (ABA). GA 4 content and pith cavity area were also highly positively correlated. These findings unravel a critical adaptation mechanism in A. philoxeroides : coordinated hormonal adjustments (GA 4 up, ABA down, higher GA 4 /ABA) and morphological remodeling (pith cavity enlargement) that synergistically support enhanced growth under severe submergence. This work advances understanding of plant adaptive strategies under climate-driven hydrological stress, enriches insights into abiotic stress response mechanisms, and provides valuable references for wetland ecosystem conservation and the improvement of crop submergence tolerance.

Due to the cutting mechanism of the existing grafting machine, it cannot adjust the cutting angle in real time, resulting in low fitting precision on the cutting surfaces between the rootstocks and scion seedlings and, thus, seriously affecting the survival rate and quality of the grafting seedlings. In this paper, a kind of splice grafting method based on visual image is proposed, aiming at maximizing the joint rate between cutting surfaces of rootstocks and scion seedlings and realizing precise cutting and grafting of grafting machine. After analysis, we determined that melon rootstock seedlings have a structure of pith cavity inside, and the solid structure from the top of the pith cavity to the left and right base points of a growing point forms the important area of a cutting surface. In order to obtain the geometric model of the cutting surfaces of the seedlings, a visual image analysis system was established to identify, analyze, and model the pith cavity structure inside the rootstock seedling, as well as the external morphological characteristics, and the ultimate cutting angle of the rootstock seedling and cutting surface parameters were determined. By measuring the length of minor axis of scion seedlings in order to achieve the maximum joint rate, the optimal cutting angle of the rootstocks and scion seedlings was determined. Then grafting and seedling cultivation tests were carried out. The test results showed that the range of ultimate cutting angle on rootstock seedlings (Cucurbita moschata) was 18.21 ± 1.92°; the cutting angles of the rootstock (Cucurbita moschata) and scion seedlings (watermelon) were 22° and 19.68°, respectively; the cutting surface length of the two was 4.96 mm; and the cutting surface thickness of the rootstock was 0.13 mm, all of which could satisfy the technological requirements of the matched splice grafting of melons. The research results can serve as a reference for the design in vision-guided precision cutting and real-time grafting operation on grafting robots.

BACKGROUND AND AIMS: Oil pollution of wetlands is a world-wide problem but, to date, research has concentrated on its influences on salt marsh rather than freshwater plant communities. The effects of water-borne light oils (liquid paraffin and diesel) were investigated on the fresh/brackish wetland species Phragmites australis in terms of routes of oil infiltration, internal gas transport, radial O₂ loss (ROL), underwater gas films and bud growth. METHODS: Pressure flow resistances of pith cavities of nodes and aerenchyma of leaf sheaths, with or without previous exposure to oil, were recorded from flow rates under applied pressure. Convective flows were measured from living excised culms with oiled and non-oiled nodes and leaf sheaths. The effect of oil around culm basal nodes on ROL from rhizome and root apices was measured polarographically. Surface gas films on submerged shoots with and without oil treatment were recorded photographically. Growth and emergence of buds through water with and without an oil film were measured. KEY RESULTS: Internodes are virtually impermeable, but nodes of senesced and living culms are permeable to oils which can block pith cavity diaphragms, preventing flows at applied pressures of 1 kPa, natural convective transport to the rhizome, and greatly decreasing ROL to phyllospheres and rhizospheres. Oil infiltrating or covering living leaf sheaths prevents humidity-induced convection. Oil displaces surface gas films from laminae and leaf sheaths. Buds emerge only a few centimetres through oil and die. CONCLUSIONS: Oil infiltrates the gas space system via nodal and leaf sheath stomata, reducing O₂ diffusion and convective flows into the rhizome system and decreasing oxygenation of phyllospheres and rhizospheres; underwater gas exchange via gas films will be impeded. Plants can be weakened by oil-induced failure of emerging buds. Plants will be most at risk during the growing season.

The paleotropical tree genus Macaranga (Euphorbiaceae) comprises all stages of interaction with ants, from facultative associations to obligate myrmecophytes. In SE.-Asia food availability does not seem to be the limiting factor for the development of a close relationship since all species provide food for ants in form of extrafloral nectar and/or food bodies. Only myrmecophytic Macaranga species offer nesting space for ants (domatia) inside internodes which become hollow due to degeneration of the pith. Non-myrmecophytic species have a solid stem with a compact and wet pith and many resin ducts. The stem interior of some transitional species remains solid, but the soft pith can be excavated. The role of different ant-attracting attributes for the development of obligate ant-plant interactions is discussed. In the genus Macaranga, the provision of nesting space seems to be the most important factor for the evolution of obligate myrmecophytism.