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A large part of the production of tomato plants is grafted. Although it has recently been described that cell walls play an important role in tomato graft healing, the spatiotemporal dynamics of cell wall changes in this critical process remains largely unknown. The aim of this work was to immunolocalize changes in the major cell wall matrix components of autograft union tissues throughout the course of healing, from 1 to 20 days after grafting (DAG). Homogalacturonan was de novo synthetized and deposited in the cut edges, displaying the low methyl-esterified homogalacturonan a stronger labelling. Labelling of galactan side chains of rhamnogalacturonan increased until 8 DAG, although remarkably a set of cells at the graft union did not show labelling for this epitope. Changes in xylan immunolocalization were associated to the xylem vasculature development throughout, while those of xyloglucan revealed early synthesis at the cut edges. Arabinogalactan proteins increased up to 8 DAG and showed scion-rootstock asymmetry, with a higher extent in the scion. The combination of these changes appears to be related with the success of the autograft, specifically facilitating the adhesion phase between scion-rootstock tissues. This knowledge paves the way for improved grafting using methods that facilitate appropriate changes in the time and space dynamics of these cell wall compounds. Key message: Immunolocalization reveals that spatiotemporal changes of cell wall components of the graft union tissue, such as homogalacturonan, xyloglucan and arabinogalactan proteins, have an important role for successful graft healing in tomato. [ABSTRACT FROM AUTHOR]

Grafting involves a sequence of modifications that may vary according to genotypes, grafting techniques and growing conditions. This process is often monitored using destructive methods, precluding the possibility of monitoring the entire process in the same grafted plant. The aim of this study was to test the effectiveness of two non‐invasive methods—thermographic inference of transpiration and determination of chlorophyll quantum yields—for monitoring graft dynamics in tomato (Solanum lycopersicum L.) autografts and to compare the results with other reliable measures: mechanical resistance parameters and xylem water potential. The mechanical resistance of grafted plants steadily increased from 6 days after grafting (DAG), 4.90 ± 0.57 N/mm, to reach values similar to non‐grafted plants at 16 DAG, 8.40 ± 1.78 N/mm. Water potential showed an early decrease (from −0.34 ± 0.16 MPa in non‐grafted plants to −0.88 ± 0.07 MPa at 2 DAG), recovering at 4 DAG to reach pre‐grafting values at 12–16 DAG. Thermographic inference of transpiration dynamics displayed comparable changes. Monitoring maximum and effective quantum yield in functional grafts showed a comparable pattern: an initial decline, followed by recovery from 6 DAG onwards. Correlation analyses revealed a significant correlation between variation in temperature (thermographic monitoring of transpiration), water potential (r = 0.87; p = 0.02) and maximum tensile force (r = 0.75; p = 0.05). Additionally, we found a significant correlation between maximum quantum yield and some mechanical parameters. In conclusion, thermography monitoring, and to a lesser extent maximum quantum yield measurements, accurately depict changes in key parameters in grafted plants and serve as potential timing indicators of graft regeneration, rendering them valuable tools for monitoring graft functionality. [ABSTRACT FROM AUTHOR]

Inula viscosa (syn Dittrichia viscosa) (sticky fleabane) from the Asteraceae family, is well-known for its pharmacological activities. In this research, anatomical characterization of leaves and stems of Inula viscosa plants revealed a considerable heterogeneity in their cell walls. Cell walls were isolated separately from leaves and stems and subjected to sequential extractions with boiling water, oxalate ammonium, KOH and NaOH solutions. The four polysaccharide fractions obtained were comparatively analysed using gas chromatography-flame ionization detector (GC-FID) and Fourier Transform Infrared–Attenuated Total Reflectance (ATR-FTIR) spectroscopy. The findings showed that the polysaccharides were unevenly distributed in the two organs. ATR-FTIR data reflected a higher proportion of pectins in stems relative to leaves in both fractions. Pectic fractions (hot water soluble and oxalate soluble fractions) seemed to be mainly composed by homogalacturonan and rhamnogalacturonan, with a residual presence of inulin. Hemicellulose (KOH and NaOH) fractions, instead, were rich in xylans, and still contained a low proportion of pectic polysaccharides. ATR-FTIR data pointed to a higher proportion of xylans in stems than in leaves. Finally, attending the molecular mass of cell wall polysaccharides from leaves, pectin fractions showed the presence of populations of polysaccharides with lower molecular masses than those of hemicellulose fractions. [ABSTRACT FROM AUTHOR]

Saxifraga paniculata is a subalpine succulent perennial plant arranged in a rosette that is usually found in shallow soil among limestone rocks. Stereoscopic, light and scanning electron microscopy were used to describe the anatomical structure of S. paniculata leaves, paying special attention to structures related to CaCO3 (calcium carbonate) release. Anomocytic stomata are unevenly distributed on each leaf face, being absent in the lower third. The basal leaf margin presents translucent pluricellular trichomes of variable length and width. Towards the apical margin, trichomes become teeth. Both trichomes and teeth are completely covered with whitish CaCO3 crystals. Each tooth has a circular cavity connected to a single hydathode through pores. Clearing treatment revealed camptodromous leaf venation. Anatomical structure shows a bifacial cross-section with spongy mesophyll cells at basal part, becoming heterogeneous at the apex with palisade mesophyll on the adaxial face. Hydathodes are epithematic and connected to outer cavities via two kidney-shaped guard cells showing large substomatal cavity. The epithem is surrounded by a thickened sheath and is formed of highly packed elongated cells with interspersed tracheary elements. CaCO3 deposits consist of microscopic crystals with varying geometries, of which the rhombus is the basic unit. [ABSTRACT FROM AUTHOR]

Grafting is a technique applied to a considerable number of crops, with tomato standing out. However, this technique is limited by the obtaining of unfunctional grafts, which decrease the success rate and therefore the benefits achieved. The aim of this work was to analyze the failure in intraspecific grafting of tomato plants, focusing on tissue development, cell wall defense reactions, and the distribution of starch and soluble sugars at the graft junction. The success rate in autografts was higher than that of homografts and heterografts. Unfunctional homografts and heterografts showed similar responses: absence of vascular reconnections and lack of adhesion between scion and rootstock, even though callus cell clusters and differentiation of new vasculature were produced. The scions of unfunctional grafts accumulated more starch and soluble sugars than the rootstocks, showing a strong asymmetry in the response. In addition, three types of deposits were observed in the cell walls of unfunctional grafts: lignin, suberin, and callose, with the combined accumulation of more than one of them being frequent, particularly lignin and suberin. These deposits apparently prevent adhesion and seem to be a major cause of graft failure. [ABSTRACT FROM AUTHOR]

Despite the importance of grafting in horticultural crops such as tomato (Solanum lycopersicum L.), the structural changes that occur during the graft establishment are little understood. Using histological techniques, the present work examines the time course of changes on the anatomical structure of the graft junction in functional tomato homografts and compares it to that of heterografts and non-functional grafts. No apparent differences were detected between homo- and heterografts, showing similar tissue development. At 10 days after grafting, the cell walls of the scion and rootstock in the area of the graft junction were thicker than usual. Undifferentiated cells and new vascular tissue emerged from the pre-existing vasculature. Adventitious roots appeared mainly on the scion, arising from the pre-existing vasculature. At 20 days, more pronounced vascular tissue was visible, along with large areas showing vascular connection. At 210 days, vestiges of the changes undergone in graft development were still visible. Generally, non-functional grafts presented layers of necrotic remains and deposition of cell wall material in the cut edges, impeding the suitable scion-rootstock connection. Our results show that accurate changes in pre-existing vasculature and the cell walls of the adhesion line are crucial to the development of functional grafts. [ABSTRACT FROM AUTHOR]