Effects of Different Photoperiods and Chilling Treatments on Growth and Reproduction of Cardamine flexuosa With. and Its Ecological Implications

Abstract Phenotypic variability of Cardamine flexuosa (Cruciferae) was examined in response to different lengths of exposure to low temperature (5°C) at the juvenile stage, and to two photoperiod regimes (8 and 16 hrs day-lengths) in the subsequent growth period. The results indicated that this species had a facultative chilling or long-day requirement for flowering. The long-day and chilling treatments both caused an earlier onset of stem internode elongation. Longer chilling treatments reduced the number of nodes and increased internode length under both long and short photoperiod regimes. Prolonged chilling treatments followed by long-day photoperiod remarkably induced more numerous basal branches and inflorescences, as a result producing more siliques. Remarkable rosette leaves Were formed at the base of the main stem when partial chilling and the short-day treatment suppressed stem internode elongation. The responses to chilling and long-day treatment closely resembled the synchronized flowering of this species in spring in the field. Delayed flowering under the short-day treatment resembled size- or age-dependent flowering in late summer to autumn in the field populations.     

Inhibitory Action of Blue and Far-Red Light in the Flowering of Lemna paucicostata

In a new strain of short-day duckweed (Lemna paucicostata T-101), blue and far-red light-induced inhibition of flowering was investigated. Flowering of this strain failed to be induced under a short-day photoperiod of blue and far-red light, although it responded as a typical short-day plant in red and white light. When the short-day photoperiod of blue or far-red light was terminated by a 15 min red light pulse, flowering recovered completely. This inducing effect of red light was reversed by subsequent exposure to far-red light. Furthermore, it could be demonstrated that 30 min of blue light completely reversed the flowering inductive effect of 5 min red light and vice versa. Evidence is presented suggesting that the inhibitory action of blue and far red light may be due to the lowering of phytochrome P_fr levels below those required to start the dark reactions which lead to flowering. These results are discussed in relation to the time measurement system of photoperiodism.     

Rhyncholites and conchorhynchs as calcified jaw elements in some late Cretaceous ammonites

Conspicuous calcareous coverings are present in the anterior region of 17 fossil jaws from late Cretaceous rocks of Hokkaido (Japan) and Sakhalin (U.S.S.R.). The jaws were preserved in calcareous nodules either in situ in body chambers of ammonites or in close association with identifiable ammonite conch remains. From the morphologic similarity between in situ and isolated jaws, they may be attributed to Tetragonites glabrus, Gaudryceras tenuiliratum, G. denseplicatum, G. sp., and Neophylloceras subramosum. The jaw apparatus of these species is composed of two three-dimensional black walls of carbonate apatite, which might be a diagenetic replacement of chitinous material. The calcareous coverings in both upper and lower jaws closely resemble those of upper (rhyncholite) and lower (conchorhynch) jaws of modern Nautilus as well as rhyncholite and conchorhynch fossils in their gross morphology, microstructure, and chemical composition. Calcified remains of cephalopod jaws known as rhyncholites and conchorhynchs have been reported from late Paleozoic to Recent. The present discovery of ammonoid rhyncholites and conchorhynchs suggests that at least some previously known late Paleozoic and Mesozoic counterparts belong to the Ammonoidea. The essential similarity of jaw elements of some Late Cretaceous ammonites and modern Nautilus gives reliable information on the feeding habits of the former. The sharp and thick ammonoid rhyncholites and conchorhynchs may have had a special function for cutting up food, similar to those of Nautilus.     

Auxin-induced growth of tuber tissue of Jerusalem artichoke IV. Significance of gibberellin biosynthesis and basic proteins in chromatin in aging process

The role of endogenous gibberellin in the aging process preparatoryto auxin action of expanding cells was studied, using tissueslices excised from cold-stored Jerusalem artichoke tuber. CCC inhibited the auxin-induced expansion growth when addedto slices during the aging period. This inhibition was alleviatedby the simultaneous addition of gibberellic acid. The amountof gibberellin-like substances increased during the aging periodand this increase was suppressed by CCC. During the aging period, acid-soluble basic proteins in thechromatin fraction decreased in amount, and exogenous gibberellicacid enhanced the decrease. (Received October 30, 1967; )     

RIBONUCLEIC ACID METABOLISM AND CELL EXPANSION IN OAT COLEOPTILE

RNA metabolism in oat coleoptiles was studied using physiologicalresponses to 5-FU and actinomycin D; autoradiographic detectionof RNA and protein synthesis; and estimation of ribosomal concentrationby analytical ultracentrifugation. 5-FU failed to inhibit growthof either intact coleoptiles or isolated coleoptile segmentsbut completely blocked cell division in roots. Actinomycin Dmarkedly inhibited auxin-induced expansion of coleoptile segments.When supplied to isolated segments from coleoptiles of variouslengths the RNA precursors cytidine, adenine and adenosine allshowed weak incorporation into RNA of nuclei and in some cases,to a lesser extent, RNA of cytoplasm. IAA did not affect thisRNA synthesis but it was considerably reduced by actinomycinD. A proportion of the label incorporated from RNA precursorswas not removable with either RNase, PCA or hot TCA but wasextracted by trypsin. The amount of this spurious incorporationincreased with coleoptile age, as did the ability to incorporatelabelled amino acids. The concentration of both free and boundribosomes does not increase in growing coleoptiles and may evendecline. Free ribosomes decline markedly in fully grown coleoptileswhile the proportion of bound ribosomes increases. It is concludedthat young coleoptiles contain a full complement of ribosomesnecessary for subsequent growth but normal growth is dependenton continued production of an actinomycin D-sensitive messenger-typeRNA. No evidence for auxin mediation of RNA synthesis was found. ¹Present address: Laboratory of Cell Biology, Faculty of Science,Osaka City University, Sugimoto-cho, Sumiyoshi-ku, Osaka, Japan.     

Further studies on the role of cell-wall-degrading enzymes in cell-wall loosening in oat coleoptiles

A fungal endo-ß-l,3-glucanase was compared with afungal exo-ß-1,3-glucanase with respect to their effectson elongation and cell-wall extensibility in oat coleoptilesegments. The exo-enzyme enhanced elongation and extensibilityof the cell wall. Its effect was not additive to the effectof indole-3-acetic acid when given together with the latter,at least during 3 hr of incubation. Endo-glucanase showed nosignificant effect on elongation and no interaction with theexo-enzyme. Auxin and exo-glucanase increased extensibilityof the cell wall. The exo-glucanase was separated by isoelectricfocusing. The two fractions which were separated and showedglucanase activity induced elongation and cell wall loosening. (Received March 16, 1970; )     

Diversification in flowering time due to tandem FT-like gene duplication, generating novel Mendelian factors in wild and cultivated rice

The complex structure of a single Mendelian factor widespread in the Asian cultivated rice ( Oryza sativa ) and its wild progenitor ( Oryza rufipogon ) that caused diverse phenotypes in the timing of flowering under natural field conditions was investigated in near isogenic lines. These near isogenic lines showed differences in flowering time despite all eight accessions collected from tropical regions possessing a recessive gene allelic to the se-pat gene. Fine mapping in two of these near-isogenic lines revealed that cultivated (Patpaku) and wild (W593) accessions had three and two linked quantitative trait loci (QTL) in the candidate regions, respectively, showing that Patpaku and W593 possessed linked QTLs with different effects in addition to the commonly-observed recessive gene ( se-pat ). Molecular dissection suggested that the tandemly duplicated FT-like genes ( Hd3a and RFT1 ) could be the candidate genes for these QTLs. Interestingly, the linked QTLs differed in their epistases, degree of dominance, and genotype × environment interactions. The nucleotide sequences showed that RFT1 has diverged more rapidly than Hd3a during rice evolution, suggesting phenotypic diversification of the two genes. Phylogenetic analysis implied that the se-pat ⁺ alleles might have emerged in different lineages within O. sativa . The present results strongly suggest that nucleotide divergence and shuffling of the linked QTLs by recombination might have created novel Mendelian factors that probably contribute to responding to local environments.     

Problems of Oocyte Maturation and the Control of Chromosome Cycles*

During oocyte maturation and zygote development chromosomes undergo cyclic changes, alternaing the condensed and decondensed states. In oocytes, zygotes and perhaps in other cells, the chromosome cycle appears to be controlled in same way by common cytoplasmic factors. Among them, maturation-promoting factor (MPF) plays a particularly important role, although the germinal vesicle substances and cytoplasmic membrane vesicles are indispensable for the chromosomal changes. MPF precursor is stored in fully grown oocytes of most species, but replenishing MPF after its fall during cell cycles requires protein synthesis. During oocyte maturation protein synthesis increases following the activation of MPF, and the synthesized proteins bind with chromosomes that have condensed to a metaphase state. The temporal correlation between the appearance of MPF with chromosome condensation activity and spindle formation observed in various cells suggest a major role played by MPF in the control of chromosome and microtubule assembly cycles. Thus, MPF is a regulator that coordinates the functions of various cell components to advance the chromosome cycle from interphase to metaphase. Therefore, a key to understanding the control of the chromosome cycle lies in knowing factors on which MPF activity is dependent. Although some physiological parameters of the cell are known to affect MPF activity, including Ca ion levels, intracellular pH, protein synthesis activity, cAMP levels, and protein phosphorylation, it seems difficult to assign the control of MPF cycles to any of these parameters. On the contrary, MPF cycles appear to regulate changes in these parameters. Rather, since MPF has the ability to amplify itself by activating its precursor, thus being involved in the MPF-generating system in the cell, the MPF cycle may be an autonomous process. This notion may be supported by the recent observation of the oscillatory activity of MPF in cytosols extracted from frog eggs. We propose theoretical models to explain the MPF oscillator in the cell.     

Effect of benzimidazole on the senescence of wheat chloroplasts and their boat shape transformation

Benzimidazole efficiently retards the senescence of detachedwheat leaves. Electron microscopic study has revealed that nodamage was visible on the fine structure of chloroplasts inleaves which retained their green color by benzimidazole treatment,whereas chloroplasts of water floated leaves showed strikingalterations in their color, shape and fine structure as senescenceproceeded. Moreover, the chloroplast lamellar system in benzimidazoletreated leaves even seemed to be organized over those in immediatelydetached leaves. The bending tendency for lamellar array within chloroplastswas more marked in benzimidazole treated leaves than in thecontrol. Chloroplasts showed, more frequently and intensely,transformation into the "boat shape" the extreme curvature ofthe granafretwork skeleton of the chloroplasts forming the keelof the boat. ¹This work was supported by Grants to Prof. E.R. WAYGOOD fromthe Canada Department of Agriculture (EMR-14) and the NationalResearch Council of Canada (PRBT-10) ²This work was undertaken during the author's stay at the Departmentof Botany, University of Manitoba, Winnipeg, Manitoba, Canada,with Fellowship granted to the author by the National ResearchCouncil of Canada, 1963–1965 (Received July 29, 1969; )