Seasonal changes in the effects of elevated CO2 on rice at three levels of nitrogen supply: a free air CO2 enrichment (FACE) experiment

Over time, the stimulative effect of elevated CO₂ on the photosynthesis of rice crops is likely to be reduced with increasing duration of CO₂ exposure, but the resultant effects on crop productivity remain unclear. To investigate seasonal changes in the effect of elevated CO₂ on the growth of rice (Oryza sativa L.) crops, a free air CO₂ enrichment (FACE) experiment was conducted at Shizukuishi, Iwate, Japan in 1998–2000. The target CO₂ concentration of the FACE plots was 200 µmol mol^?1 above that of ambient. Three levels of nitrogen (N) were supplied: low (LN, 4 g N m^?2), medium [MN, 8 (1998) and 9 (1999, 2000) g N m^?2] and high N (HN, 12 and 15 g N m^?2). For MN and HN but not for LN, elevated CO₂ increased tiller number at panicle initiation (PI) but this positive response decreased with crop development. As a result, the response of green leaf area index (GLAI) to elevated CO₂ greatly varied with development, showing positive responses during vegetative stages and negative responses after PI. Elevated CO₂ decreased leaf N concentration over the season, except during early stage of development. For MN crops, total biomass increased with elevated CO₂, but the response declined linearly with development, with average increases of 32, 28, 21, 15 and 12% at tillering, PI, anthesis, mid‐ripening and grain maturity, respectively. This decline is likely to be due to decreases in the positive effects of elevated CO₂ on canopy photosynthesis because of reductions in both GLAI and leaf N. Up to PI, LN‐crops tended to have a lower response to elevated CO₂ than MN‐ and HN‐crops, though by final harvest the total biomass response was similar for all N levels. For MN‐ and HN‐crops, the positive response of grain yield (ca. 15%) to elevated CO₂ was slightly greater than the response of final total biomass while for LN‐crops it was less. We conclude that most of the seasonal changes in crop response to elevated CO₂ are directly or indirectly associated with N uptake.     

Larval morphology and phylogenetic position of Horelophopsis hanseni Satô et Yoshitomi (Coleoptera,Hydrophilidae, Horelophopsinae)

The subfamily Horelophopsinae was originally proposed as one of the earliest diverging clades of Hydrophilidae (s.s.), but its phylogenetic placement has never been tested. We describe the larva of Horelophopsis hanseni Satô et Yoshitomi, 2004 of the Horelophopsinae. Larval data are based on larval specimens collected together with adults, and unambiguously associated with them by means of DNA barcoding. We perform an analysis testing the phylogenetic position of H. hanseni based on larval and adult morphological characters. Horelophopsis hanseni is unambiguously placed within the hydrophilid subfamily Hydrophilinae and its close relationships to the genus Agraphydrus Régimbart, 1903 (Hydrophilinae, Acidocerini) is recognized. The results suggest that the subfamily Horelophopsinae is unlikely to be a basal taxon of Hydrophilidae, as originally suggested.     

CELL-BINDING SUBSTANCES IN SEA URCHIN EMBRYOS*

Properties of ovacquenin, a reaggregation-promoting substance from sea urchin embryos, were further studied and compared with those of hyalin, a calcium-insoluble protein of the hyaline layer surrounding the sea urchin embryo. Properties of hyalin were basically in agreement with previous reports, but differed in some aspects. Hyalin and ovacquenin were very similar in various aspects and were hard to distiguish generally, but they were separated by ammonium sulfate fractionation. Hyalin was precipitated at a low salt concentration, while ovacquenin remained soluble until the salt concentration exceeded half saturation. Therefore it was concluded that hyalin and ovacquenin are very much alike but distinct from each other. Probable relation of ovacquenin to hyalin was discussed.     

STUDIES ON MUSCLE DIFFERENTIATION. V. ANTIGENICITIES OF MYOSIN AND OF ACTIN FROM FROG SKELETAL MUSCLES1

Both intact and denatured preparations of myosin and actin from frog skeletal muscles produced in rabbits antisera containing antibodies against authentic myosin and actin, respectively, though being contaminated with antibodies against other proteins. Antigenicity of our frog myosin as revealed in agar diffusion tests was indistinguishable from that of cardiac muscle myosin from the same species. Similarly, skeletal muscle myosins from other amphibians shared to a certain extent immunological characteristics with our frog myosin, but those from avian and mammalian materials did not. Similarity in antigenicity was also demonstrated among our skeletal muscle actin, cardiac muscle actin from the same species and skeletal muscle actin from the other anurans studied. However, skeletal muscle actin from an urodele could not clearly be correlated in its immunological properties with our frog actin, and those from avian and mammalian materials were antigenically different from our frog actin. Thus, the degree of antigenic similarity of these muscle proteins seemed to be correlated with the phylogenic relationship of the animals so far studied. The results also indicated that our antisera could only be applied to immuno-cytological and immuno-embryological studies of myosin and actin when the antisera absorbed with the corresponding antigen preparations were used as negative controls.     

DEMONSTRATION AND PRELIMINARY CHARACTERIZATION OF REAGGREGATION-PROMOTING SUBSTANCES FROM EMBRYONIC SEA URCHIN CELLS

Morulae or early blastulae of sea urchins dissociate readily on treatment with isotonic urea containing EDTA. During dissociation a certain substance was extracted. This substance was found to accelerate reaggregation of dissociated cells. The manifestation of the reaggregation-accelerating activity of the substance requires rather complicated handling of divalent cations. On the basis of these findings, a working hypothesis on the mode of function of the substance is presented.
Some properties of the substance were investigated and were found to be very similar to those of hyalin, the calcium-insoluble protein of the hyaline layer surrounding the fertilized egg.     

The growth promoting effect of phytic acid on callus tissues of rice seed

The effects of phytic acid, myo-inositol hexaphosphoric acid,in the induction and growth of rice seed callus were studied.Phytic acid was substituted for myo-inositol in the inductionof the callus and preferable effects were shown on the growthof the callus. ¹Present address: Hyogo Agricultural Experiment Station, Akashi,Hyogo, Japan (Received June 30, 1970; )     

Thinning of the basement Membrane and Localized Cell Proliferation during Gland Formation of the Chick Proventriculus

The early processes of proventricular gland formation in the chick embryo were investigated. The glands appeared as intra-epithelial invaginations of the proventricular endoderm on day 6 of incubation. By day 6.5 they began to protrude into the mesenchyme and elongated without branching until day 9. Before elongation of the glands, the immunofluorescence of laminin and the ultrastructure of the basal lamina were consistently observed in the intra-epithelial invaginations as well as in other regions, and the mitotic activity in the gland rudiments was not different from that in other regions. However, at the tips of the elongating glands, little laminin was detected and the basal lamina were thin and discontinuous. The mitotic activity at the tip of the glands was higher than that in non-glandular epithelium or in the stalk of the glands. These results suggest causal relationships between thinning of the basement membrane and localized epithelial cell proliferation at the tip of the elongating glands.     

Density dependent shifts in attachment site by the ectosymbiotic chironomid Nanocladius asiaticus on its megalopteran host Protohermes grandis

Intraspecific interactions among ectosymbionts may occur when suitable attachment sites are limited to specific parts of their hosts. In this study, we examined attachment site selection by the ectosymbiotic chironomid Nanocladius (Plecopteracoluthus) asiaticus. Larvae and pupae of this chironomid attach to larvae of the megalopteran Protohermes grandis: they feed on algae and detrital materials caught on the chironomid's silken nets and on the body surface of the host. Sampling at approximately monthly intervals in central Japan revealed that the proportion of hosts with chironomids was relatively high and stable during the 2 year study period. When attached singly, larvae were usually found on the ventral side of the host's mesothorax. However, when two or more larvae were attached to a host, the mesothorax was occupied by only one larva (usually a large individual) and the other(s) were attached to the ventral side of the abdomen. Density dependent shifts in attachment sites were confirmed by a reattachment experiment in which a larva was removed from its host and released onto a new host with or without symbiosis by another individual. All of the larvae released singly on a host devoid of symbionts attached to the thoracic region and survived, whereas those released in pairs and not occupying this site were frequently lost. Thus, the thorax (particularly the mesothorax) is the most suitable attachment site, and there is a possibility that chironomid larvae compete for this site.