ROLE OF CALCIUM IN POTASSIUM UPTAKE BY PLANT ROOTS

The effects of EDTA·Mg or GEDTA·Mg on the uptakeof nutrient ions, the release of Ca⁺⁺ and nucleotides into themedium and the nucleic acid contents in rice and red bean rootswere investigated.

1. Both EDTA and EDTA·Mg induced similarly the release ofCa from roots.
2. EDTA·Mg as well as EDTA brought abouta significant repressionin K uptake, but had an insignificantor no effect on P, NH₄and NO₃ uptakes. EDTA·Ca did notrepress K, P, NH₄ andNO₃ uptakes.
3. EDTA or GEDTA acceleratedthe degradation of nucleic acid andthe release of nucleotides,while EDTA·Mg or GEDTA·Mghad no such effect.

These results indicate that the indispensable role of intracellularCa in K uptake does not appear to be directly associated withRNA metabolism. (Received July 29, 1965; )     

Respiratory Utilization of 13C-Labelled Photosynthate in Nodulated Root Systems of Soybean Plants

Kouchi, H., Akao, S. and Yoneyama, T. 1986. Respiratory utilizationof ¹³C-labelled photosynthate in nodulated root systems of soybeanplants.—J. exp. Bot. 37: 985–993. An improved method for the measurement of respiratory utilizationof current photosynthate in the nodulated root system of water-culturedsoybean (Glycine max L.) plants was developed using a steady-state¹³CO₂ labelling technique. Well-nodulated plants at the latevegetative stage were allowed to assimilate ¹³CO₂ for 10 h incontinuous light at a constant CO₂ concentration with a constant¹³C abundance. The respiratory evolution of ¹³CO₂ from rootsand nodules was measured continuously throughout the periodof ¹³CO₂ assimilation and during a subsequent 36 h chase periodby using a differential infrared ¹³CO₂ analyser. The plantswere grown with nitrogen-free or (15 mmol dm^–3)-containing culture solution for 3 d before¹³CO₂ assimilation. In plants grown without , nodule respiration averaged 69% of the total respiration of the undergroundparts over the full experimental period and the CO₂ respiredreached an apparent isotopic equilibrium at 80–85% labellingafter initiating ¹³CO₂ assimilation. By contrast, the CO₂ respiredfrom the roots did not reach an isotopic equilibrium and labellingwas only 56% at the end of exposure to ¹³CO₂ These findingsdemonstrated that nodule respiration is strongly dependent onrecently assimilated carbon compared with root respiration. Plants supplied with in the culture solution showed a decreased rate of nodule respirationand a slightly increased rate of root respiration. The extentsand time courses of labelling of respired CO₂ from both theroots and nodules were similar in the presence and absence of except that the maximum level of labelling of CO₂ derived from nodule respiration in plantswith was significantly higher (about 91%) than for plants growing without . Key words: Soybean (Glycine max L.), nodule respiration, ¹³CO₂, assimilation, carbon partitioning     

Distribution of the Germinal Vesicle Material during Progesterone-Induced Oocyte Maturation in Xenopus and in Cynops

The distribution of the germinal vesicle material in the oocyte during progesterone-induced maturation was studied in Xenopus and in Cynops. In both species, two distinctive masses of yolkfree cytoplasm appear in specific areas of the oocyte and at definite stages of maturation. One, the primary cytoplasmic mass, is formed at the basal side of the germinal vesicle during early maturation and is very RNA-rich. In Xenopus , a large part of the primary cytoplasmic mass persists as a mass during maturation and ends up as a thin disk at the boundary between the animal and the vegetal hemisphere in the mature oocyte. In Cynops , a rod-like primary cytoplasmic mass extends near to the equatorial zone and becomes indistinct in the mature oocyte. The other, the secondary cytoplasmic mass, is formed at or prior to germinal vesicle breakdown in areas around the germinal vesicle and is also RNA-rich. The secondary cytoplasmic mass is dispersed and constitutes the RNA-rich animal hemisphere cytoplasm in the mature oocyte. Observed results suggest that the primary and the secondary cytoplasmic mass contain different germinal vesicle materials.     

THE EFFECTS OF TEMPERATURE ON THE GERMINATION AND RADICLE GROWTH OF PHOTOSENSITIVE LETTUCE SEED

1. The time course of germination of Grand Rapids lettuce seedshas heen followed with different combinations of temperature(3°–35°) and irradiation (red or far-red light).For each set of conditions the following three parameters weredetermined: (i) the time required for half maximum germination,(ii) the rate of germination during the actively germinatingphase, and (iii) the maximum germination attained. In general,as the temperature was lowered, with dark-imbibed seeds, (i)became longer, (ii) became lower, but (iii) became progressivelyhigher. The effect of red light at any temperature was to shorten(i) and increase (ii) and (iii) over the values dark controls.Far-red light exerted an effect opposite to that of red light.Temperatures higher than 25° inhibited (ii) and (iii) underany light conditions. The optimum temperature to the actionof red and far-red light is 25°, at which the stimulatoryeffect of red light and the inhibition of this effect by far-redlight are both maximal. 2. The growth of the radicles of de-coated seeds of Grand Rapidslettuce shows two phases at all temperatures studied. PhaseI is characterized by slow but linear growth which continuesuntil shortly after visible differentiation of the radicle intothe hypocotyl and the root. Phase II is a phase of active growthin which the total length reflects mainly the length of theroot. The optimum temperature for Phase I is 25°-35°,and that, for Phase II is 25°. In neither phase, and atnone of the temperatures studied, is there any effect of redor far-red radiation on the growth of the radicle. The firstvisible sign of radicle elongation in red light induced seeds,however, takes place at exactly the same time as that of germination. 3. Similarities and dissimilarities between the germinationand the growth are pointed out, and it is concluded that thetwo phenomena are different, but proceed at sites closely associatedin the embryo. ¹Present address: Johnson Foundation for Medical Physics, Universityof Pennsylvania, Philadelphia, Pa., U.S.A.     

CONASSIMINEA, A NEW GENUS OF THE ASSIMINEIDAE (CAENOGASTROPODA: RISSOOIDEA) FROM SOUTHEASTERN AUSTRALIA

A new genus of Assimineidae, Conassiminea, is described fromestuarine habitats in southeastern Australia (New South Wales,Tasmania and Victoria). Two new species, C. studderti and C.zheni, are included in the genus, the former being the typespecies. Conassiminea is distinct from all other assimineidgenera in two autapomorphies in the female reproductive system:the seminal receptacle has two ducts and the bursal duct isextremely wide. The phylogenetic relationships of the new genuswere examined using a morphological dataset. (Received 26 February 2005; accepted 22 April 2005)     

Comparison of genetic variation and differentiation using microsatellite markers among three rare threatened and one widespread toad lily species of Tricyrtis section Flavae (Convallariaceae) in Japan

Genetic diversities were examined using six microsatellite markers amplifiable in three rare and one widespread species of Tricyrtis section Flavae, which are endemic to Japan. Contrary to a general expectation, the three rare species, Tricyrtis flava, Tricyrtis ohsumiensis and Tricyrtis perfoliata, have comparable genetic variation at the species level to that of the widespread Tricyrtis nana. This is probably because T. nana has not sufficiently recovered genetic diversity from the bottleneck at speciation or because recent range contractions have occurred in the three rare species. Genetic diversity at the population level was smaller in the putative selfing species T. nana than in the other three outcrossing species. Compared with a preceding study using allozyme markers, the genetic diversity in microsatellite loci was considerably larger, probably resulting from higher mutation rates at the microsatellite loci. Owing to the high genetic diversity of the microsatellite markers, genetic differentiation among populations could be estimated even in T. nana with little allozyme polymorphism.     

Diverse diet compositions among harpaline ground beetle species revealed by mixing model analyses of stable isotope ratios

1. Species diversities of some insect lineages have been attributed to differentiation of feeding habits among species. Our objective was to determine variation in diet composition among harpaline ground beetle species occurring in a riverside grassland. 2. We examined the diet compositions of 14 species from six genera in the spring and 10 species from two genera in the autumn. We performed measurements of nitrogen and carbon stable isotope ratios in consumers and in their potential food items, and estimated relative contributions of different food items with two mixing models, IsoSource and MixSIR. 3. IsoSource and MixSIR software gave similar results, but IsoSource tended to calculate higher contributions of principal food items and smaller percentile ranges than MixSIR. Among harparine beetle species, there were diverse food utilisation patterns among four food categories (detritivorous invertebrates, herbivorous invertebrates, C3 plants, and C4 plants). Detritivores comprised the main diets of abundant harpaline species in the spring, whereas abundant harpaline species in the autumn were primarily herbivores feeding on C4 plants, or omnivores feeding on herbivorous invertebrates and C3 plants. Seasonal changes in food use were related to seasonal changes in the abundance of each food resource. 4. Mixing model analysis of stable isotope ratios is a convenient and effective method for roughly estimating diets of many species with diverse food habits (such as ground beetles). This method can contribute to determining the trophic relationships of related insects in one ecosystem.