Development of Ascorbate Oxidase Activity and Its Iso-enzyme Pattern in the Roots of Pea Seedlings

Early in the germination of peas, ascorbate Oxidase activity increased markedly in the root and epicotyl, but not in the cotyledons. The activity in the root was suppressed by the administration of 6-methylpurine, thiouracil, cyclohexi-mide, thioproline, and phenylthiourea. Although enzyme development was inhibited by phenylthiourea and thioproline, root elongation was not affected by these reagents. As germination progressed, the ascorbate oxidase activity in the extract of the seedling's root could be separated into at least 3 to 7 isoenzymes.     

Increased Reproductive Allocation of Rumex japonicus Caused by Leaf Clipping

Abstract To elucidate the effects of herbivory by chrysomelid beetles on Rumex japonicus, rosette leaves were clipped and the subsequent fruit production and root growth were observed. The increase of leaf biomass of some clipped plants was greater than that of control plants, although this varied among individual plants. The root growth of clipped plants was less than that of control plants. Fruit production increased with plant size, and there was no difference in fruit production between clipped and control plants. Reproductive allocation (fruit biomass, relative to fruit biomass plus root growth) increased with plant size; it was greater in clipped plants than in control ones. Based on these results, reproductive allocation strategy against herbivory was discussed.     

Pollinator Restriction in the Narrow-tube Flower Type of Mertensia ciliata (James) G. Don (Boraginaceae)

Abstract Mertensia ciliata (Boraginaceae) includes two flower types with different corolla tube widths, wide and narrow. The former is pollinated by both queens and worker bumblebees, while the latter type is pollinated exclusively by bumblebee workers. Morphological comparisons between the flowers and the bumblebees showed that the relationship between the width of the corolla tube mouth and the head width of the bumblebee is a primary factor restricting pollinators to workers in the narrow-tube type. Length of the proboscides and corolla tube are of secondary importance for this restriction, since some queens are not able to reach the bottom of a narrow corolla tube even if their proboscis is extended fully.     

Phosphorylation of Deoxyribonucleosides and DNA Synthesis during Embryogenesis of the Sea Urchin

The phosphorylation of thymidine, deoxycytidine, deoxyadenosine and deoxyguanosine was studied during the embryogenesis of the sea urchin Hemicentrotus pulcherrimus. [³H]Thymidine was taken up, phosphorylated and accumulated mostly as [³H]thymidine triphosphate in the early cleavage stage embryos. As the embryos developed, the formation of [³H]thymidine triphosphate decreased and most of the [³H]thymidine taken up by the blastulae remained be phosphorylated. When [³H]deoxycytidine was added to the cleaving embryos, the resultant labeled pool consisted of almost equal amounts of [³H]deoxycytidine monophosphate and [³H]deoxycytidine triphosphate. The formation of [³H]deoxycytidine monophosphate increased up to 10 hr following fertilization and then decreased, while the formation of [³H]deoxycytidine triphosphate decreased for 10 hr following fertilization and then gradually increased. [³H]Deoxyadenosine was rapidly phosphorylated to monophosphate derivative in the cleavage stage embryos. The formation of [³H]deoxyadenosine triphosphate increased rapidly after cleavage stage with a concomitant decrease of [³H]deoxyadenosine monophosphate. The activity of phosphorylation in [³H]deoxyguanosine to triphosphate derivative increased rapidly reaching a plateau 10 hr after fertilization. At this point, 80 % of the [³H]deoxyguanosine was recovered as [³H]deoxyguanosine triphosphate. Based on the above results, it was concluded that the profile of production of each deoxyribonucleoside triphosphate changed during the embryogenesis of the sea urchin, and the in vivo rate-limiting step of phosphorylation of the individual deoxyribonucleoside was assumed to be different.     

Changes in the Nitrogen Compounds of Xylem Sap of Mulberry (Morus alba L.) during Regrowth after Pruning

Changes in fresh and dry weights and total nitrogen in stemsections of mulberry (Morus alba L.) and seasonal fluctuationin the amounts of exudate, pH and nitrogen compounds in xylemsap from cut stems of the plant after pruning have been studied.The amount and concentrations of nitrogen compounds in the sapchanged during the experimental period, but nitrate-nitrogenand ammonia-nitrogen were constant constituents, and asparaginewas quantitatively the major organic nitrogen compound. Smalleramounts of glutamine, aspartic acid and glutamic acid were alsofound, but no ureides or alkaloids were detected. Relationshipsbetween growth and nitrogen in xylem sap of mulberry and therole and importance of asparagine in nitrogen metabolism arediscussed. Morus alba L., mulberry, asparagine, exudates, nitrogen, amino-acids, xylem sap, stem growth, aspartic acid, glutamic acid, ureides     

Neural Induction by Treatment with Ca2+-free Saline Solution in the Gastrula Ectoderm of Cynops pyrrhogaster and Inhibition of Neural Induction with Fetal Calf Serum

The relation between the inducing activity and the cell-dissociation effect of Ca²⁺-free (or Ca²⁺, Mg²⁺-free) saline solution (CF or CMF) on the early gastrula ectoderm was examined. In the culture medium containing no fetal calf serum (FCS), most ectoderm cells treated with CF or CMF died within a few days and only a few differentiated into epidermal cells. However, when the culture medium contained 2% FCS, ectoderm cells treated with CF or CMF differentiated into neural crest derivatives (NCDs), such as mesenchyme cells, pigment cells, and nerve cells. The frequency of the induction depended only on the duration of CF- or CMF-treatment. FCS alone had no inducing activity on ectoderm cells. On the contrary a high concentration of FCS gave an inhibitory effect on the induction. These results indicate that CF is a neuralizing factor and that CF-treated cells require FCS, not for induction, but for survival and differentiation. With CF, the maximum induction of NCDs required a longer duration than that necessary for complete cell-dissociation. This result suggests that the induction depends on some effects of CF other than cell-dissociation.     

Red and far-red reversible photoreactions on seed germination of Cucumis sativa

The effects of red and far-red light in seed germination ofCucumis sativa differs markedly with the degree of seed ripeningand the variety of seed; reciprocal hybrids are clearly maternal. (Received December 26, 1968; )