Non-Structural Carbohydrates and Catalytic Activities of Sucrose Metabolizing Enzymes in Trunks of Two Juglans Species and their Role in Heartwood Formation

Abstract

Summary In trunks of Juglans nigra and the hybrid J. major × J. regia, the presence of non-structural carbohydrates, sucrose synthesizing and degrading enzymes, and their correlation with heartwood formation was investigated. Contents of starch and sucrose were highest in the youngest sapwood, decreased with increasing age of the tissue, and were absent in the heartwood. Pools of the monosaccharides glucose and fructose were low in the sapwood, and fructose was absent from the heartwood. Glucose transiently increased at the sapwood heartwood boundary in trunks of the hybrid. In black walnut stems, however, glucose started to accumulate within the transition zone and reached considerable amounts in the heartwood. Cold-adaptation in walnut wood was characterized by accumulation of soluble sugars. Sucrose formation was enabled by enhanced rates of sucrose-phosphate synthase (SPS, EC 2.4.1.14). Mid-winter starch-sugar interconversion was accompanied by increases in the activity of sucrose synthase (SuSy, EC 2.4.1.13; black walnut), or acid invertases (EC 3.2.1.26; hybrid). In the tissues undergoing heartwood formation, sucrose breakdown was enhanced from late summer until early winter. Sucrolysis was dominated by acid invertases with minor contribution of sucrose synthase. The catalytic activity of UDP-glucose pyrophosphorylase (EC 2.7.7.9), involved in the metabolization of the sucrose cleavage products, followed this seasonal trend and showed elevated activities from late summer until early winter. These data are further proof for the earlier made hypothesis (Hauch and Magel 1998) that the in situ synthesis of heartwood flavonoids relies on an interaction between primary (sucrose) and secondary metabolism. Flavonoids, however, constitute only a minor fraction in the heartwood of walnut and the bulk of heartwood phenolics seem to derive from transformation of phenolic precursors. Therefore, these recent findings together with earlier data are taken as evidence that more than one type of heartwood formation exists.

Histochemical and Anatomical Studies of Phloem and Xylem Cells of Jackfruit (<i>Artocarpus heterophyllus</i> Lam.) Tree

“…A number of studies have provided information on distribution of protein in both deciduous and coniferous trees. The information of protein heterophyllus supported the previous investigations [5][6][7] . Abundant presence of protein droplets within xylem ray parenchyma cells indicated that the ray tissue in the secondary xylem of woody plants plays an important role in the translocation, storage, and mobilization of nutrients [17] .…”

“…Such types of accumulation and localization of reserve materials (e.g. starch, lipid and protein) between phloem and xylem cells is well known from extended studies on different trees [5,6,12,18] , rather than jackfruit. The results showed clearly the information of localization of reserve materials of A. heterophyllus but their intracellular localization and specific function, are still obscure.…”

“…There have been several reports of variations in levels and partitioning of storage starch, lipid droplets, proteins in trees such as in Betula pendula [4] , Pinus sylvestris [5] ; Juglans nigra and hybrid Juglans major × J. regia [6] , Pinus cembra [7] , Quercus petraea and Fagus sylvatica [8][9] . The data in the cited studies indicate that levels of different reserve materials from phloem to xylem provides one of the key to a full understanding of growth and development of trees.…”

Distribution of starch, lipid and nuclei in xylem and phloem of Tectona grandis Linn.

“…There have been several reports of variations in levels and partitioning of storage starch granules, lipid droplets in trees, e.g. Betula pendula (Harms and Sauter 1992), Pinus sylvestris (Fischer and Höll 1992); Juglans nigra and hybrid Juglans major × J. regia (Magel et al 2001), Pinus cembra (Hoch et al 2002), Quercus petraea and Fagus sylvatica Breda 2002, Barbarous et al 2003). The data in the cited studies indicate that levels of different reserve materials from phloem to xylem provides one of the key to a full understanding of growth and development of trees.…”

Effects of the Temperature Lowered in the Daytime and Night-time on Sugar Accumulation in Sugarcane

“…A low temperature increases sucrose production in Arabidopsis by promoting fructose-1,6-bisphosphatase and sucrose phosphate synthase (SPS), the two key regulated enzymes in sucrose synthesis that leads to a shift in carbon partitioning to sucrose (Strand et al, 1999;Stitt and Hurry, 2002). The activity of enzymes in the sucrose synthesis pathway increases during cold acclimatization in the leaves of spinach (Martindale and Leegood, 1997), winter wheat, rye and rape (Hurry et al, 1994(Hurry et al, , 1995, and in walnut wood (Margel et al, 2001). Post-transcriptional activation of SPS occurs in potato tubers (Hill et al, 1996;Deiting et al, 1998;Krause et al, 1998), apple fruits (Duque et al, 1999) and cabbage seedlings (Sasaki et al, 2001) exposed to low temperatures.…”