Mesophyll conductance decreases in the wild type but not in an ABA‐deficient mutant (aba1) of Nicotiana plumbaginifolia under drought conditions

Under drought conditions, leaf photosynthesis is limited by the supply of CO₂. Drought induces production of abscisic acid (ABA), and ABA decreases stomatal conductance (g_s). Previous papers reported that the drought stress also causes the decrease in mesophyll conductance (g_m). However, the relationships between ABA content and g_m are unclear. We investigated the responses of g_m to the leaf ABA content [(ABA)_L] using an ABA‐deficient mutant, aba1, and the wild type (WT) of Nicotiana plumbaginifolia. We also measured leaf water potential (Ψ_L) because leaf hydraulics may be related to g_m. Under drought conditions, g_m decreased with the increase in (ABA)_L in WT, whereas both (ABA)_L and g_m were unchanged by the drought treatment in aba1. Exogenously applied ABA decreased g_m in both WT and aba1 in a dose‐dependent manner. Ψ_L in WT was decreased by the drought treatment to ?0.7 MPa, whereas Ψ_L in aba1 was around ?0.8 MPa even under the well‐watered conditions and unchanged by the drought treatment. From these results, we conclude that the increase in (ABA)_L is crucial for the decrease in g_m under drought conditions. We discuss possible relationships between the decrease in g_m and changes in the leaf hydraulics.     

Development of compound microsatellite markers in the harmful dinoflagellate Cochlodinium polykrikoides (Dinophyceae)

We isolated 15 polymorphic microsatellites from Cochlodinium polykrikoides. These loci provide a class of highly variable genetic markers, as the number of alleles ranged from two to 15, and the estimate of gene diversity was from 0.083 to 0.880 across the 15 microsatellites. We consider that these loci have a potential to reveal the genetic structure and gene flow among C. polykrikoides populations.     

Pathway of mannitol formation during photosynthesis in brown algae

Eisenia bicyclis, Arame, was allowed to photosynthesize in seawatercontaining H¹⁴CO₃^–, and ¹⁴C-mannitol was isolated fromits fronds. The ratio of ¹⁴C-total/¹⁴C₁ + ¹⁴C₆ in the ¹⁴C-mannitolwas found to be about 8.0 at 1 min-illumination, but graduallydecreased with time to 3.0, showing uniform radioactivity distribution.Mannitol therefore seems to be formed in brown algae throughthree carbon compounds. Enzymes which may be involved in the possible biosynthetic pathwayof mannitol, i.e. aldolase, hexose diphosphatase, mannitol-1-phosphataseand glucosephosphate isomerase were present in extracts fromseveral brown algae. Some of their properties are discussed. ¹Contribution from the Shimoda Marine Biological Station ofTokyo Kyoiku University, No. 187. ²Present address: Reseach Institute, Seikagaku Kogyo Co., Ltd.,Yamato-machi, Kitatama-gun, Tokyo, Japan. (Received December 13, 1968; )     

THIS ARTICLE HAS BEEN RETRACTEDDevelopment of microsatellite markers in the noxious red tide‐causing dinoflagellate Heterocapsa circularisquama (Dinophyceae)

We isolated 15 polymorphic microsatellites from one of the most noxious red tide‐causing dinoflagellate species, Heterocapsa circularisquama. These loci provide one class of highly variable genetic markers, as the number of alleles ranged from two to six, and the estimate of gene diversity was from 0.205 to 0.684 across the 15 microsatellites. These loci have the potential to reveal genetic structure and gene flow among H. circularisquama populations.     

Development of microsatellite markers for the Manila clam Ruditapes philippinarum

We isolated nine polymorphic microsatellites from the Manila clam Ruditapes philippinarum. These loci provide one class of highly variable genetic marker as the number of alleles ranged from six to 22, and the observed and expected heterozygosity ranged from 0.136 to 0.909 and from 0.553 to 0.954, respectively. We consider that these loci are potentially useful for detailing the genetic structure and gene flow among R. philippinarum populations.     

中国秋海棠属植物的传统利用

秋海棠属植物除了具有较高的观赏价值外,在中国还作为药用、食用、饮料和饲料等被利用。本文应用民族植物学研究方法,通过野外调查、文献和标本收集整理和研究,共记载了中国产26种秋海棠属植物被作为药用、食用、饮料和饲料加以利用。在所记载的26种国产秋海棠属植物中,有24种作药用,8种作食用(蔬菜)或饮料,5种作饲料。3种作饮料的种类在其自然分布地被广泛利用。9种秋海棠作为多种用途加以利用,其中8种既被作为药用、食用和饮料,也被作为饲料加以利用。本研究还表明,国产秋海棠属植物中,有些种类由于过度采集利用或其它因素已变得稀有或濒危。由此提出,合理开发利用和有效保护应成为今后中国秋海棠属植物研究的重要内容。     

The Effect of Hydrocortisone on the Epidermal Proliferation in an Organ Culture of Chick Embryonic Skin

Hydrocortisone is regarded as an initiator of keratinization in embryonic skin. The present investigation dealt with the effect of hydrocortisone on the proliferation of epidermal cells during early development: Cell kinetic analyses using ³H-thymidine autoradiography were applied to a skin organ culture prepared from a 13-day chick embryo.
Hydrocortisone at a concentration between 0.01 and 1.0 μg/ml was effective in initiating a morphological change leading to the epidermal keratinization in vitro and caused a marked decrease in the mitotic and labeling indices of epidermal basal cells, the decrease being maximum at 2 days of culture previous to the morphological change.
During continuous labeling with ³H-thymidine, the number of labeled basal cells reached 100% within 2 days in the control and 4 days in the culture treated with hydrocortisone. This confirmed that the growth fraction of epidermal basal cells was 1.0 even after the administration of hydrocortisone.
The duration of each cell cycle phase at 2 days of culture was determined by percent labeled mitoses and double-labeling analyses. It was concluded that hydrocortisone extended the generation time of epidermal basal cells at this time point about three fold over the control. This extension was mainly due to the elongation of the G ₁ phase.     

EFFECTS OF THYROXINE AND PROLACTIN ON THE RATES OF PROTEIN SYNTHESIS IN THE THIGH BONES OF THE TADPOLE OF RANA CATESBEIANA

In thigh bones isolated from a Rana catesbeiana tadpole which has been kept in a 5 × 10⁻⁸ M thyroxine solution for several days, the rate of ¹⁴C-leucine incorporation into protein becomes higher than that in the thigh bones of control animals. Intraperitoneal injection of prolactin also results in an increase in the rate of ¹⁴C-leucine incorporation into protein in the thigh bones at a rate very similar to that in thyroxine-treated animals. In the thigh bones of the thyroxine-treated tadpoles, the rate of ¹⁴C-proline incorporation into protein is markedly higher than that of control animals. Prolactin treatment of the tadpoles also causes an increase in the rate of ¹⁴C-proline incorporation, but the rate is lower than that found in thyroxine-treated animals. The injection of prolactin into thyroxine-treated tadpoles fails to cause further increase in the rates of incorporation of these amino acids into protein. In the thigh bones of tadpoles at the climax of metamorphosis, prolactin injection does not cause any increase in the rates of ¹⁴C-labeled proline and leucine incorporation, whereas both rates become slightly higher in the thigh bones of thyroxine-treated tadpoles at this stage. The thigh bones probably become insensitive to prolactin when they are exposed to thyroxine.     

Transverse Vein Differentiation Associated with Gas Space Formation--Fate of the Middle Cell Layer in Leaf Sheath Development of Rice

In monocotyledons, the leaf vascular network consists of a hierarchicalsequence of vertical vascular bundles and numerous transverseveins that interconnect adjacent vertical veins. In the leafsheath of these species, especially grasses, lysigenous gascavities (gas spaces) are developed into intervascular spacesand provide a gas conducting system to non-aerial parts underflooded conditions. The spatial relationship between gas spaceformation and transverse vein differentiation was investigatedusing the leaf sheath of rice (Oryza sativa L.). Histochemicalobservation showed that patterns of differentiation of the transversevein are distinct from those of vertical vascular bundles. Onthe other hand, gas spaces are formed through the processesof cell death (collapse). Both events are initiated at a specificcell position in the middle layers of the leaf sheath, fromwhich the vascular system of the leaf is derived; this indicatesthat differentiation of transverse veins is associated withgas space formation. The cell-to-cell movement of fluoresceinisothiocyanate-conjugated dextran injected into middle layercells coincided with the area where cell collapse occurred,indicating a close relationship between the middle and adaxialcell layers, but not abaxial cell layers. A uniform cell numberbetween each transverse vein in the leaf sheath suggested theinvolvement of spatial regulation in transverse vein formationregardless of clonal history at the later stage of leaf veincanalization. Copyright 2000 Annals of Botany Company Cell collapse, leaf development, middle cell layer, microinjection, Oryza sativa L., rice, programmed cell death.