Atsushi Takimoto

Comparative studies on the absorption of cadmium and copper in Lemna paucicostata

Abstract The absorption of copper or cadmium in Lemna paucicostata 6746 was suppressed by the addition of EDTA to the medium. Only 30 μm of EDTA was sufficient to prevent the absorption of copper at a concentration of 5–10 μ m whereas 400 μ m of EDTA was necessary to prevent the absorption of cadmium at the same concentration as copper. Ammonium ion added to the medium also greatly suppressed copper absorption. Cadmium absorption was, however, only slightly suppressed by this means. The growth of Lemna under these experimental conditions was inhibited in proportion to the amount of copper or cadmium absorbed. The absorption of cadmium was higher, the higher the initial pH of the medium, but that of copper was not significantly affected by the initial pH between 3·6 and 5·1. Nonetheless, both cadmium and copper inhibited plant growth more strongly at pH 5·1 than at pH 4·1. The absorption mechanism and the mode of action of cadmium seem to differ from those of copper in Lemna paucicostata 6746.

Effects of cadmium and copper co-existing in the medium on the growth and flowering of Lemna paucicostata in relation to their absorption

Abstract Copper ion added to M-sucrose medium suppressed both frond multiplication and frond growth (wet weight increase of each frond) of Lemna paucicostata 6746, but cadmium ion suppressed only frond multiplication not affecting frond growth. Such ion specific actions of copper and cadmium were evident even in the medium containing both metal ions, the degree of their effects depending on the concentration of each metal ion absorbed. The absorption of copper was not influenced by the presence of cadmium but that of cadmium was reduced considerably with increasing concentrations of copper in the medium. The flower-inducing activity of copper ion in this plant was nullified by simultaneous application of cadmium which does not suppress either copper absorption or short-day induced flowering.

LEMNA AS AN INDICATOR OF WATER POLLUTION AND THE ABSORPTION OF HEAVY METALS BY LEMNA

ABSTRACT To determine the potential for use of Lemna paucicostata 6746 as an indicator of water pollution, and for its utilization as a purifier of waste water, and to study the biokinetics of heavy metals, the sensitivity of Lemna to heavy metals and the mode of metal absorption by Lemna were studied. The concentration factor of cadmium for Lemna was from approximately 100 to 500 at the 24th hour after the start of culture on Bonner-Devirian medium containing cadmium (pH6.1). Seven days after the start of culture, 70% of cadmium in 25ml of medium was absorbed by Lemna on 0.01ppm cadmium-containing medium, 50% on 0.1ppm, and 2% on 1ppm cadmium-containing medium. Those factors which make Lemna more sensitive to cadmium–the high pH value of the medium, dilution of the medium, and high temperature– were also effective in causing the rapid absorption of cadmium by Lemna. The frond multiplication of Lemna for 7 days was inhibited 50% by 0.1ppm of cadmium or copper, and by 1ppm of zinc, manganese or arsenic. Arsenic and copper inhibited the growth of each frond more effectively than frond multiplication, whereas zinc, manganese and cadmium primarily inhibited frond multiplication.

Action spectra for photogene expression in etiolated pea seedlings

Action spectra (responsivity spectra) for the transcript accumulation of four photogenes, rbcS, rbcL, Cab and psaB, had a major peak in the red region (660 nm). Violet (400 nm) and green (510 nm) light also induced these transcripts, but their effects differed with the gene. The effect of red light was reversed by later exposure to far‐red light, but the effects of violet and green light were not. Non‐reversible photoreactions in addition to the phytochrome‐mediated photoreversible reaction seemed to be involved in the expression of these photogenes.

Flowering response oflemna paucicostata in japan

Twenty-two strains ofLemna paucicostata collected from various districts in Japan are classified into 4 types having different morphological features and photoperiodic behaviors. (I) The “N-1” type, widely distributed in north and middle Japan, consists of many short-day strains with similar morphological characteristics. The strain of northern origin, however, has a shorter critical dark period than that of southern origin, and most of the strains flower in response to a single short day though some from middle Japan require 2 short days. (2) The “N-2” type, found in a limited area of northern Japan, is also a short-day type, but has very long critical dark periods and requires 3–5 short-day cycles for flowering. (3) The “S” type, distributed in southern Japan, never flowered in any photoperiod or culture conditions tested. (4) The “K” type, strain 351, collected at the experimental farm of Kyoto University, is a day-neutral type and flowers independently of photoperiod.Application of some SH inhibitors, tungstate or EDTA, or exposure to blue, far-red or low-intensity light caused daylength-independent flowering in short-day strain 6746 (California origin), but none of these treatments caused flowering in any short-day strain collected in Japan.

ATP‐GTP‐BINDING PROTEINS AND ENDOGENOUS ADP‐RIBOSYL TRANSFERASE IN Lemna paucicostata 441

Abstract— A crude extract containing membrane components of Lemna paucicostata was treated with 1% Lubrol PX and fractionated by gel nitration. Binding activities to non‐hydrolyzable analogues of ATP, [35S]ATPγS (adenosine 5′[;γ‐thio]triphosphate) and that of GTP, [35S]GTPγS (guanosine 5′[γ‐thiojtriphosphate) were detected in some fractions, and these activities were prevented in the presence of 0.1 mM ATP or GTP. ATP and GTP were 2 to 3 orders of magnitude more effective than CTP or UTP in preventing this binding activity. These fractions showed ATPase and GTPase activities with 1 nM [γ‐32P]ATP or [γ–32P]GTP substrate. Analyses by sodium dodecyl sulfate polyacrylamide gel electrophoresis of these fractions after binding with [35S]ATPγS or [35S]GTP‐γ S revealed that these fractions contained [35S]ATPγS and [35S]GTPγS binding proteins with molecular weights of 53 000 and 60 000, respectively. Both of these proteins were [32P]ADP‐ribosylated by endogenous ADP‐ribosyl transferase. Three proteins with molecular weights of 11 000, 12 000 and 13 000 which could bind [35S]ATP7S or [‐35S]GTP‐γ S were ADP‐ribosylated by endogenous ADP‐ribosyl transferase. Pertussis toxin stimulated ADP‐ribosylation of these proteins. Four proteins with molecular weight of 37 000, 50 000, 80 000 and 115 000 with PSS]ATP7S and [,3S]GTP7S binding activities were also detected. The signal transduction of light to underlying clock mechanism in Lemna may be controlled by ATP‐GTP‐binding proteins and by the ADP‐ribosylation of these proteins.

FLUENCE‐RESPONSE RELATIONSHIP FOR PHOTOGENE EXPRESSION IN ETIOLATED PEA SEEDLINGS†

Fluence‐response relationships in transcript accumulation were investigated at various wavelengths for the following photogenes: the nuclear‐encoded small subunit gene of ribulose bisphosphate carboxylase/oxygenase (rbcS), the nuclear‐encoded chlorophyll alb‐binding protein gene (Cab), the chloroplast‐encoded large subunit gene of ribulose bisphosphate carboxylase/oxygenase (rbch) and the chloroplast‐encoded photosystem I A2 subunit gene (psaB). The fluence‐response curves for all genes obtained at all wavelengths showed a biphasic character suggesting the involvement of both very low fluence response and low fluence response mediated by phytochrome. The proportion responding in the very low fluence range differed with the gene, and was largest for rbcL followed by psaB, Cab and rbcS in this order.

Further studies on the flowering ofLemna paucicostata in Japan

Flowering behavior of 22 strains ofLemna paucicostata collected in Japan by Yukawa and Takimoto (1976) was re-examined. The critical dark periods of the short-day strains (N-1 and N-2 types) were shorter than those determined by Yukawa and Takimoto except for that of one strain. Particularly in strains 391, 381 and 321, the differences were as large as 2.25, 1.75 and 1.5 hr, respectively. Such differences were found to be due at least partly to the difference in night temperature; 25 C for the light and 23 C for the dark periods in the present experiment, and 25 C throughout the light and dark periods in the previous experiment. The S type strains did not flower under our experimental conditions (fluorescent light of 6,000 lux at 25 C) at any photoperiod tested, but flowered as a quantitative long-day plant under natural daylight or high-intensity light (12,000 lux). Addition of sucrose or ammonium ion to the medium suppressed the flowering of these strains under high-intensity light.Addition of benzoic acid (1–5 μM) to 0.5 strength NH4+-free Hutners medium caused daylength-independent flowering in some N-1 type strains and in all N-2 type strains tested. S type strains cultured under fluorescent light of 6,000 lux also flowered rapidly in response to benzoic acid.

Geographical distribution and cytological variation ofLemna paucicostata Hegelm. in Japan

More than 100 strains ofLemna paucicostata Hegelm. collected from various localities in Japan were classified into 4 types according to the criterion of Yukawa and Takimoto (1976). N-1 type strains are widely distributed in Hokkaido, Honshu, Shikoku and Kyushu, N-2 type strains only in the area on the Japan Sea side of north Japan, K type strain only at the campus of Kyoto University, and S type strains in southern Japan.Numbers of chromosomes in somatic cells of N-1, N-2, K and S type strains were 2n=66–84, 40, 50 and 40, respectively. In N-2 and S type strains, all chromosomes (20 bivalent chromosomes) were lined up on the equatorial plate at metaphase of the first meiotic division (MI). However, in N-1 type strains, several chromosomes, and in the K type strain, more chromosomes were away from the equatorial plate at MI. Pollen fertility was 60–70%, higher than 90%, 0% and higher than 90%, in N-1, N-2, K and S type strains, respectively.

Growth of various ecotypes ofLemna paucicostata in Japan under various temperature conditions, and their wintering forms

Lemna paucicostata in Japan is classified into 4 types, N-1, N-2, K and S types. S type strains which are distributed in southern Japan grew more rapidly than other strains at the temperatures of both 27 and 17C. With the extension of the culture period at 17 C to which the plants had been transferred from 25C, the growth rate increased greatly in S type strains, while it decreased in N-1 type strains which are distributed widely from Hokkaido to Kyushu, and particularly in those distributed in the northern area. S type strains survived winter mostly in the form of normal fronds under natural conditions at Kyoto (minimum temperature is lower than OC), while most of the fronds of N-1 type strains died after producing seed before winter. Thus S type strains are considered to have adapted to the climate of southern Japan so as to survive winter in the form of fronds, while N-1 type strains overwinter in the form of seed. N-2 type strains which are distributed in the northern part of the area adjacent to the Japan Sea produced turion-like fronds during winter under natural conditions, while none of the other strains did. The K type strain which was found only at the campus of Kyoto University overwintered only in the form of fronds which produce no seed.