The application of various anatomical techniques for studying the hydraulic network in tomato fruit pedicels

Abstract

The abscission zone in fruit pedicels plays an important role in affecting not only water uptake in the developing fruit, but also in the transport of chemical signals from root to shoot. In order to characterize the hydraulic network of tomato fruit pedicels, we applied various techniques, including light, fluorescence microscopy, electron microscopy, maceration, tissue clearing, and X-ray computed tomography. Because of significant changes in xylem anatomy, the abscission zone in tomato fruit pedicels is illustrated to show a clear reduction in hydraulic conductance. Based on anatomical measurements, the theoretical axial xylem conductance was calculated via the Hagen-Poiseuille law, suggesting that the hydraulic resistance of the abscission zone increases at least two orders of magnitude compared to the pedicel zone near the stem. The advantages and shortcomings of the microscope techniques applied are discussed.

Abscission of flowers and floral organs is closely associated with alkalization of the cytosol in abscission zone cells

“…The tomato FAZ is typically composed of 5–10 rows of small cells, which traverse the pedicel at the site of an indentation of the epidermis. The FAZ cells, however, are not lined up, and there are regions that can contain >20 rows of cells ( Rančić et al , 2010 ; Iwai et al , 2013 ). Nonetheless, the pattern of fluorescence changes during tomato flower pedicel abscission, as seen in cross- and longitudinal sections of the FAZ ( Figs 6 , 7 ), were similar to the pattern of GUS staining of the Tomato Abscission PG4 ( TAPG4 ) gene in cross- and longitudinal sections of the tomato FAZ following ethylene-induced abscission ( Hong et al , 2000 ).…”

How to quantify conduits in wood?

“…Samples can be injected in an acropetal or basipetal direction without differences in vessel length distribution. However, it is known that spatial distribution patterns of vessels near nodes, side branches, and petioles of leaves and flowers can be significantly different from an otherwise random vessel distribution (Salleo et al, 1984; André et al, 1999; Rancić et al, 2010). In general, we recommend injecting basipetally, selecting an injection point that avoids side branches, nodes, and leaves as much as possible.…”

“…Traditionally, rather limited attention has been paid to the spatial distribution of vessels and their possible role in the hydraulic system of plants. Earlier work based on the connectivity between vessels has illustrated that vessels are usually randomly arranged (Zimmermann and Tomlinson, 1966; Braun, 1970) except near nodes and in leaf and flower abscission zones (Salleo et al, 1984; André et al, 1999; Rancić et al, 2010). Furthermore, vessels nearly always start and end in connection to another vessel, which means that vessels do not end or start blindly (Zimmermann and Tomlinson, 1966; Braun, 1970).…”

TheSEPALLATA MADS‐box proteinSLMBP21 forms protein complexes withJOINTLESSandMACROCALYXas a transcription activator for development of the tomato flower abscission zone

“…Abscission is a dynamically regulated process by which plants shed their organs. Organ abscission is an essential step in the plant life cycle, whether for the removal of aging leaves to mitigate damage from snow load or drought stress, or for the shedding of seeds to guarantee their dispersal (Sexton and Roberts, ; Reid, ; Roberts et al ., , ; Rančić et al ., ). For most plants, abscission occurs at a specific region, named the abscission zone (AZ).…”