Tamizi Sugiyama

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.

Biological activities and structure-activity relationship of substitution compounds of N-[2-(3-indolyl)ethyl]succinamic acid and N-[2-(1-naphthyl)ethyl]succinamic acid, derived from a new category of root-promoting substances, N-(phenethyl)succinamic acid analogs

In a previous study, it was demonstrated that N-(phenethyl)succinamic acid (PESA) derivatives form a new category of root-promoting substances which do not exhibit auxin-like activities, such as stem elongation and leaf epinasty (Soejima et al., 2000 [Plant Cell Physiol. 41s: 197]). In this study, N-[2-(3-indolyl)ethyl]succinamic acid (IESA) and N-[2-(1-naphthyl)ethyl]succinamic acid (NESA) were synthesized, and their biological activities were evaluated. In an adzuki root-promoting assay, IESA and NESA exhibited root-promoting activity equivalent to PESA. In adzuki stem elongation assays, elongation activity was not observed in the stem segments soaked in either an IESA or NESA aqueous solution, whereas the stem segments immersed in Indole-3-acetic acid (IAA) or 1-naphthylacetic acid (NAA) aqueous solution were clearly elongated. In an epinastic bending study, IAA and NAA exhibited leaf epinasty, whereas IESA and NESA did not, suggesting that the IESA and NESA derivatives belong to the same category of root-promoting substances as PESA derivatives and are different from auxin-like substances. In addition, eleven kinds of IESA derivatives and nineteen kinds of NESA derivatives were synthesized, and their root-promoting activities were measured. The activities of methyl ester derivatives were approximately three times higher than that of the acid compounds, with exceptions for some compounds. The partition coefficient (P) between 1 -octanol and water for each IESA, NESA, and PESA derivative was measured in order to evaluate the hydrophobicity of their molecules and to determine their structure—activity relationship. The results indicate that the root-promoting activity of the acid compounds was significantly correlated with their hydrophobicity, whereas that of ester derivatives was not correlated.