Takafumi Kubo

Relationships between cambial activity, cell differentiation and the localization of starch in storage tissues around the cambium in locally heated stems of Abies sachalinensis (Schmidt) Masters

A study was made, in a cool-temperate zone, of the extent of cell division in the cambium, the extent of differentiation of cambial derivatives, and the localization of storage starch around the cambium in locally heated (22–26°C) stems of the evergreen conifer Abies sachalinensis (Schmidt) Masters during cambial dormancy and immediately after natural reactivation of the cambium. In locally heated regions of stems during cambial dormancy, heating induced localized reactivation of the cambium. However, the cells in the heated and reactivated cambium stopped dividing soon after only a few cells had been generated. In addition, no differentiation of the xylem and the disappearance of starch from storage tissues around the cambium were observed. In regions of stem that had been locally heated after natural reactivation of the cambium, cell division continued in the cambium and earlywood tracheids with a large radial diameter and secondary walls were formed, with abundant starch in the storage tissues around the cambium. Our results suggest that the extent of both cell division in the cambium and cell differentiation depends on the amount of starch in storage tissues around the cambium in the locally heated stems of an evergreen conifer growing in a cool-temperate zone.

Cambial reactivation in locally heated stems of the evergreen conifer Abies sachalinensis (Schmidt) masters

Abstract. A study was made of cambial activity, the localization of storage starch around the cambium, and the localization and occurrence of microtubules in cambial cells from dormancy to reactivation in locally heated (22–26 °C) stems of the evergreen conifer Abies sachalinensis. Heating induced localized reactivation of the cambium in the heated portions of the stem. Erect ray cambial cells resumed cell division 1 d prior to the reactivation of fusiform cambial cells and procumbent ray cambial cells. The re-initiation of the division of fusiform cambial cells occurred first on the phloem side. During the heat treatment, the amount of storage starch decreased in procumbent ray cambial cells and in the phloem parenchyma adjacent to the cambium but increased in fusiform cambial cells. Preprophase bands of microtubules, spindle microtubules and phragmoplast microtubules were observed both in erect ray cambial cells and in procumbent ray cambial cells. By contrast, no evidence of the presence of such preprophase bands of microtubules was detected in fusiform cambial cells. The results suggest that the localized heating of stems of evergreen conifers might provide a useful experimental model system for studies of the dynamics of cambial reactivation in intact trees.

The positional distribution of cell death of ray parenchyma in a conifer, Abies sachalinensis

We monitored the distribution of death of secondary xylem cells in a conifer, Abies sachalinensis. The cell death of tracheids, which are tracheary elements, occurred successively and was related to the distance from cambium. Thus, it resembled programmed cell death. By contrast, the death of long-lived ray parenchyma cells had the following features: (1) ray parenchyma cells remained alive for several years or more; (2) in many cases, no successive cell death occurred even within a given radial cell line of a ray; and (3) the timing of cell death differed among upper and lower radial cell lines and other lines of cells within a ray. These results indicate that the death of long-lived ray parenchyma cells involves a different process from the death of tracheids. The initiation of secondary wall formation and the lignification of ray parenchyma cells in the current years annual ring were delayed in the upper and lower radial cell lines of a ray. In addition, the density of distribution and orientation of cortical microtubules in such cells were different from those in cells in other radial lines. Ray parenchyma cells in the previous years annual ring within the upper and lower radial cell lines of a ray contained many starch grains. Our results indicate that positional information is an important factor in the control of the pattern of differentiation and, thus, of the functions of ray parenchyma cells that are derived from the same cambial ray cells.

Differences in patterns of cell death between ray parenchyma cells and ray tracheids in the conifers Pinus densiflora and Pinus rigida

Differences in patterns of cell death between ray parenchyma cells and ray tracheids in the conifers Pinus densiflora and Pinus rigida were clarified. Differentiation and cell death of ray tracheids occurred successively and both were related to the distance from the cambium. In this respect, they resembled those of longitudinal tracheids. Thus, the cell death of short-lived ray tracheids could be characterized as time-dependent programmed cell death. In contrast, ray parenchyma cells survived for several years or more, and no successive cell death occurred, even within a single radial line of cells in a ray. Thus, the features of death of the ray parenchyma cells were different from those of ray tracheids. Cell death occurred early in ray parenchyma cells that were in contact with ray tracheids. The initiation of secondary wall thickening occurred earlier in ray parenchyma cells that were in contact with ray tracheids in Pinus densiflora than in others. In addition, localized thickening of secondary walls occurred only in ray parenchyma cells that were in contact with ray tracheids in Pinus rigida. Moreover, no polyphenols were evident in such cells in either species. Therefore, ray parenchyma cells that were in contact with ray tracheids appeared not to play a role in the formation of heartwood extractives. Our observations indicate that short-lived ray tracheids might affect the pattern of differentiation and, thus, the functions of neighboring long-lived ray parenchyma cells in conifers.

Changes in the localization and levels of starch and lipids in cambium and phloem during cambial reactivation by artificial heating of main stems of Cryptomeria japonica trees.

BACKGROUND AND AIMS Cambial reactivation in trees occurs from late winter to early spring when photosynthesis is minimal or almost non-existent. Reserve materials might be important for wood formation in trees. The localization and approximate levels of starch and lipids (as droplets) and number of starch granules in cambium and phloem were examined from cambial dormancy to the start of xylem differentiation in locally heated stems of Cryptomeria japonica trees in winter. METHODS Electric heating tape was wrapped on one side of the stem of Cryptomeria japonica trees at breast height in winter. The localization and approximate levels of starch and lipids (as droplets) and number of starch granules were determined by image analysis of optical digital images obtained by confocal laser scanning microscopy. KEY RESULTS Localized heating induced earlier cambial reactivation and xylem differentiation in stems of Cryptomeria japonica, as compared with non-heated stems. There were clear changes in the respective localizations and levels of starch and lipids (as droplets) determined in terms of relative areas on images, from cambial dormancy to the start of xylem differentiation in heated stems. In heated stems, the levels and number of starch granules fell from cambial reactivation to the start of xylem differentiation. There was a significant decrease in the relative area occupied by lipid droplets in the cambium from cambial reactivation to the start of xylem differentiation in heated stems. CONCLUSIONS The results showed clearly that the levels and number of storage starch granules in cambium and phloem cells and levels of lipids (as droplets) in the cambium decreased from cambial reactivation to the start of xylem differentiation in heated stems during the winter. The observations suggest that starch and lipid droplets might be needed as sources of energy for the initiation of cambial cell division and the differentiation of xylem in Cryptomeria japonica.

Changes in levels of endogenous plant hormones in cambial regions of stems of Larix kaempferi at the onset of cambial activity in springtime

The total amounts of endogenous indole-3-acetic acid (IAA), cytokinins, and abscisic acid (ABA) were quantified by gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) in cambial regions of the main stems ofLarix kaempferi during the spring season. During the sampling period, cambium in the dormant state entered the active meristematic state. The total amount of IAA did not change at the onset of cambial reactivation but increased when the active division of cambial cells became apparent. Four cytokinins —trans- andcis-ribosylzeatin (RZ),N6-isopentenyladenine (iP),N6-isopentenyladenosine (iPA) — were quantified, but no zeatin (Z) was detected. The total amount of the four cytokinins together and the total amount of isopentenyl-type cytokinins (iP and iPA) varied during the sampling period but did not appear to be specifically associated with cambial activity. The total amounts oftrans- andcis-RZ remained relatively constant during the sampling period, as did the total amount of ABA. The results suggest that there is little correlation between total amounts of endogenous plant hormones in the cambial region and reactivation of the cambium during the spring.

Distribution of indole-3-acetic acid and compression wood formation in the stems of inclined Cryptomeria japonica.

Many physiological investigations have been carried out to clarify the mechanism of compression wood formation, which generally occurs on the lower sides of branches and inclined stems in conifers (Tlmell 1986). The application of a high concentration of indole-3-acetic acid (IAA) to vertical stems induced compression wood formation at the application point (Balatinecz and Kennedy 1968; Blum 1970; Casperson and Hoyme 1965; Fr ser 1949; Hejnowicz and Tomaszewski 1969; Onaka 1940; Starbuck and Phelps 1986; Wardrop and Davies 1964; Wershing and Bailey 1942). The application of morphactin or 1-N-naphthylphthalamic acid (NPA), which are inhibitors of the basipetal transport of IAA, to vertical stems also induced compression wood formation just above the treatment point (Phelps et al. 1974,1977; Smolinski et al. 1972; Yamaguchi and Shimaji 1980). Furthermore, auxin activity s estimated by bioassay was higher on the lower sides of stems and branches where compression wood had formed than on the upper sides (Necesany 1958; Onaka 1942).These findings suggest that a high concentration of IAA is probably correlated with compression wood formation.

Somatic embryogenesis from immature and mature zygotic embryos of Cryptomeria japonica I: Embryogenic cell induction and its morphological characteristics

Embryogenic cells (ECs) of sugi (Cryptomeria japonica D. Don) were induced from immature and mature zygotic embryos cultured on different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D)-containing modified Campbell and Durzan medium. The rate of induction of ECs varied depending on the stage of embryos collected. The highest percentage of induction (35%) was obtained with immature zygotic embryos collected July 18 and July 30, 1997, when 1 μM of 2,4-D was added to the induction medium. The ECs easily proliferated when subcultured in a medium of the same composition as the induction medium within 3 weeks. Morphological characteristics of nonembryogenic cells and embryogenic cells of different developmental stages were studied under an inverted fluorescence microscope.

Radial variations in the anatomical characteristics and density of the wood of Acacia mangium of five different provenances in Indonesia

The anatomical characteristics and density of wood were examined in 23-year-old Acacia mangium trees that had been planted in Yogyakarta, Indonesia. The seeds had been collected from trees of five different provenances. The distance from the pith of the boundary between juvenile and mature wood was also examined to clarify the maturity of the wood. Lengths of wood fibers near the pith and the distance from the pith of the boundary between juvenile and mature wood differed significantly among provenances. By contrast, other anatomical characteristics of the wood such as fiber wall area, fiber wall thickness, fiber diameter, vessel lumen area, vessel diameter, vessel frequency and wood density did not differ significantly among provenances. Wood density was strongly correlated with the area of fiber walls. Our observations suggest that Sidei and Daintree might be more appropriate provenances among those examined for the Acacia mangium tree-breeding programs in Indonesia that are aimed at improving wood quality, because these provenances are associated with longer initial wood fibers and narrower juvenile areas than the other provenances studied.

Chiral discrimination with regioselectively substituted cellulose esters as chiral stationary phases

Four kinds of cellulose derivatives, including two regioselectively substituted cellulose esters (6-O-acetyl-2,3-di-O-benzoyl cellulose and 2,3-di-O-acetyl-6-O-benzoyl cellulose), were synthesized so that the effects of their functional group distribution on their chiral discrimination ability could be examined. The degree of substitution by functional groups appeared to have a critical effect on the separation in most cases, but the type of the functional group at the C-6 position also significantly influenced chiral discrimination when a series of neutral arylalcohol derivatives were used as racemates. Copyright 2000 Wiley-Liss, Inc.