Compartmentation of Solutes and Water in Developing Sugarcane Stalk Tissue

Abstract

Previous studies have suggested that the apoplast solution of sugarcane stalk tissue contains high concentrations of sucrose, but the accuracy of these reports has been questioned because sucrose leakage from damaged cells may have influenced the results. In this study, the solute potential of the apoplast and symplast of the second (immature), tenth, twentieth, thirtieth, and fortieth internodes of field-grown sugarcane ( determine the extent of solute accumulation in the apoplast as well as the symplast. Two independent methods were used to quantify the water relations of both the symplast and apoplast in terms of i'', ',, and i&p. Specific objectives were to measure 'I, /,, and ,6p for both mature and immature tissue, to determine how the partitioning of solutes and water between the apoplast and symplast changes with development, to identify the solutes present in each compartment, and to determine the relative volume of the apoplast solution in order to assess its importance as a storage compartment for sucrose. MATERIALS AND METHODS Plant Material.Sugarcane (Saccharum spp. hybrid, cv H65-7052) plants were field-grown in a silty-clay loam (Typic Torrox) soil near Waipahu, Oahu, HI. Well-watered 1.5-to 2-year-old plants were excised prior to sunrise when guttation water was present on leaf margins, indicating that the plants were fully hydrated. After excision, plants were immediately sealed in plastic bags and transported to the laboratory. Tissue samples were collected and analyzed on the basis of internode number. The reference point for determining internode number was the TVD leaf (12); the youngest leaf whose blade is fully exposed and not enclosed in the sheaths of older leaves. The first internode was the node below the TVD leaf sheath attachment, and additional internodes were numbered consecutively down the stalk. A 2-year-old sugarcane stalk grown under the conditions described above typically contained approximately 50 internodes. In this study, internodes 2, 10, 20, 30, and 40 were analyzed.Internode tissue sections were prepared for analysis inside a humidified chamber to reduce water loss. The stalk was cut in half at least 1 cm from the node and the epidermis and any pith tissue was removed with a knife, because the fiber content is higher and sucrose concentrations lower in these tissues (3,6

Gradients of Turgor, Osmotic Pressure, and Water Potential in the Cortex of the Hypocotyl of Growing Ricinus Seedlings

“…On the other hand, the centrifugation of segments of pea stems gave values of 70 mm (6). Results from internodes of sugarcane and from long-term equilibration of empty seed coat halves suggested some 300 mm or even more (10,30). For the Ricinus hypocotyl investigated and reported in this paper, it is remarkable to note that both low values and fairly high values can be found, depending on the rate of water supply to the tissue.…”

Developmental Changes in Cell and Tissue Water Relations Parameters in Storage Parenchyma of Sugarcane

“…We deem this unlikely because the quantity in the apoplast was greater than could be expected from cut surfaces and we rinsed the tissue blocks to remove cell debris before experimentation; a significant in situ 7CW is reported by others on intact growing tissue (3) and mature storage tissue of red beet (14) and sugar beet (25), sugarcane (22), and Kalanchoe leaves (16); and moisture release data (12) and compartmental analyses data (7,9) support the present finding of a high 7rcw in situ in sugarcane parenchyma tissue. The high rcw could have resulted from either phloem unloading into the apoplast (1,8,13,15) or from turgor-induced leakage from the storage cells (25), or both.…”

“…Turgor is apparently held low by buildup of solutes in the apoplast. High concentrations of apoplastic solutions have been reported in root (14, 25), stem (3,7,22), leaf (12), and seed coat (13) tissues of a variety of plant species. Despite this phenomenon, it is not clear whether turgor is actively controlled in cells of higher plants ( 18,20), as it is in some brackish water algae (2,19).…”

Genetic Control of Carbon Partitioning in Grasses: Roles of Sucrose Transporters and Tie-dyed Loci in Phloem Loading

“…Sugarcane internodes have the remarkable ability to store massive amounts of Suc, depositing it in both the vacuoles of stem storage parenchyma cells and the apoplast surrounding these cells (Welbaum and Meinzer, 1990). To prevent apoplastic backflow of Suc to the phloem, the stem veins are surrounded by sclerenchyma cells, which contain suberin and lignin in their cell walls (Walsh et al, 2005).…”