Changes in Endogenous Growth Regulators in the Gladiolus Corm during Dormancy

Changes in endogenous growth regulators in gladiolus corms during dormancy were studied using paper and column chromatography followed by a bioassay with the test for straight growth of Avena coleoptile. Corms were grown in the field or in a glass room of a phytotron at 20°C in the light. Another lot was grown in a dark room at 20°C in the dark. Half of the daughter corms in each lot were cold-treated for about one month and the other half were stored at room temperature after harvest. The earliest sprouting was seen in dark grown corms with cold treatment, and the latest sprouting in light grown corms without cold. This pattern was similar in each cultivar over a period of three years. Corms from both lots contained considerable amounts of inhibiting substance just after harvest. However, dark grown corms treated with cold showed a rapid decrease in inhibitor activity and an increase in promoter activity. On the other hand, in light grown corms without cold treatment there was inhibitor activity found consistently even after two months. —There appear to be two inhibiting zones in the chromato-grams. One of these contains two inhibitory substances, one of which was assumed to be abscisic acid.     

Selective light transmittance of translucent bracts in the Himalayan giant glasshouse plant Rheum nobile Hook. f. & Thomson (Polygonaceae)

Translucent bract transmittance of ultraviolet (UV) to infrared (IR) radiation (between 320 and 800 nm) and leaf anatomy were examined in a glasshouse plant, Rheum nobile Hook. f. & Thomson (Polygonaceae) to assess the function of avoiding injury by UV radiation while keeping the inflorescence warm by photosynthetically active (PA) and IR radiation. Although the translucent bracts and rosulate leaves transmitted little UV radiation, the former always transmit more PA and IR radiation. Additionally, the bracts transmit much more scattered solar radiation than direct radiation. The bracts are also anatomically different from the rosulate leaves. They have two or three layers of mesophyll cells with neither palisade nor spongy parenchymatous cells; in addition, the uppermost layer of mesophyll and the epidermis stain easily, and both are thought to play a role in attenuating UV radiation. The leaf epidermis of many land plants has UV absorbing pigments such as flavonoids, which absorb almost all UV radiation. Thus the role of the bracts of R. nobile is to protect the reproductive organs by absorbing UV radiation and to keep them warm by transmitting PA and IR radiation. The bracts are believed to have adapted function and form to the environment, in particular, to the weather conditions of the eastern Himalaya.     

Maturation-Inducing Substances in Asteroid and Echinoid Oocytes

In starfish a hormonal peptide, gonad-stimulating substance(GSS), which is released from nervous tissue, acts on the gonadto produce a maturation-inducing substance (MIS), an inducerof oocyte maturation and spawning. MIS is 1-methyladenine (1-MA).This substance acts on the surface of the oocyte. Cytoplasmicmaturation as revealed by fertilizability is also induced by1-MA. The amount of 1-MA can be determined very accurately witha bioassay method using isolated oocytes. In 1-MA formation,GSS seems to enhance the methylation of some compound whichcontains a purine nucleus at its N1 site. The methyl donor isprobably S-adenosylmethionine. 1-Methylated precursor seemsto be transformed to 1-methyl AMP and then hydrolyzed into 1-methyladenosineand phosphate by phosphomonoesterase. 1-Methyladenosine is finallysplit into 1-MA and ribose by 1-methyladenosine ribohydrolase.So-called spontaneous maturation of oocytes isolated in seawater is due to the action of 1-MA produced in follicle cellseven in the absence of GSS. 1-MA is present in echinoid gonadsand seems to act as MIS also in these animals. Disulfidereducingagents such as dithiothreitol and 2,3-dimercapto-1-propanolinduce starfish oocyte maturation. On the other hand, sulfhydrylreagents such as p-chloromercuribenzoate, iodoacetamide, andN-ethylmaleimide suppressed 1-MA-induced oocyte maturation.Since Concanavalin A acts on the follicle cells to produce 1-MA,the action of this substance seems to be quite similar to thatof GSS.     

INDUCTION OF SPAWNING AND OOCYTE MATURATION IN STARFISH BY 1-METHYL-ADENOSINE MONOPHOSPHATE

l-Methyladenosine monophosphate (l-McAMP) induces ovulation and oocyte maturation when applied to isolated ovarian fragments of Asterina pectinifera . However, isolated oocytes fail to mature even in the presence of this substance. When ovarian or testis fragments are incubated with l-McAMP, the supernatant of the incubation mixture acquires the maturation-inducing activity. Also, superantants of gonadal homogenates incubated with l-McAMP have the capacity to convert it to a maturation-inducing substance, suggesting that l-McAMP is decomposed to l-methyladenine, which is believed to be a general inducer of oocyte maturation and ovulation in starfishes. Thus l-MeAMP seems to be an intermediate in l-methyladenine formation when the latter is produced under the influence of the gonad-stimulating hormonal peptide.     

Morphological difference and reproductive isolation: morphometries in the millipede Parafontaria tonominea and its allied forms

Thin-plate spline and other multivariate statistical methods were used to examine the variation in genital morphology and body size in 74 populations of the millipede Parafontaria tonominea and its allied forms in central Japan. Although the study populations included nine sympatric pairs of two reproductively isolated forms, the variations in genital morphology and body size observed were continuous across the study group. Analyses of the sympatric pairs using bootstrapping revealed that the degree of morphological difference between sympatric populations varied considerably from pair to pair. These results demonstrate that the degree of difference in genital morphology and body size may not correspond with the establishment of reproductive isolation. Significant correlation in the pattern of geographic variation was observed for many combinations of morphological components. However, it was not possible to detect a significant correlation between morphology and geographic distance in many of the morphological components studied. This study suggests that the incorporation of genital characters in classification should be done carefully, particularly for animal groups with low vagility, such as millipedes.     

DISTRIBUTION OF MATURATION-PROMOTING FACTOR IN STARFISH OOCYTE STRATIFIED BY CENTRIFUGATION

In starfish, cytoplasm taken from maturing oocytes is capable of inducing breakdown of the germinal vesicle and subsequent maturation when injected into immature oocytes. The cytoplasmic factor has been designated as "maturation-promoting factor" (MPF). Ooplasm was stratified by centrifugation of maturing oocytes in density-graded Ficoll-seawater, without disrupting the cell. Three strata were distinguished beginning with the centripetal side: oil cap, hyaline layer and yellow layer. MPF activity was shown to be localized in the hyaline layer. Electron microscopic observation revealed that the hyaline layer contains Golgi complexes, many lucent vesicles and multi-vesicular bodies as distinct organelles, but seldom contains such inclusions as the lipid droplets forming the oil cap, mitochondria, yolk and pigment granules contained in the yellow layer. Based on these observations, a possible cytoplasmic component with MPF activity is discussed.     

BINDING OF CONCANAVALIN A TO THE SURFACE OF STARFISH FOLLICLE CELLS AND PRODUCTION OF 1-METHYLADENINE

Starfish follicle cells, treated with concanavalin A (Con A), continued to produce 1-methyl-adenine (1-MeAde), an inducer of starfish oocyte maturation, after rinsing with artificial seawater (ASW). On the other hand, they ceased to produce the substance if treated with methyl α-Dmannoside (αMM). These cells produced again 1-MeAde when re-stimulated with Con A after removal of αMM. An optical study with fluorescein revealed that Con A bound to the cells was not dissociated by rinsing with ASW, but was removed if the cells were treated with αMM. These results suggest that continuous binding of Con A to the surface of the follicle cells is essential for the production of 1-MeAde.