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171.
172.
Nutrient-uptake and nutrient-use efficiency ofPinus thunbergii Parl. along a topographical gradient of soil nutrient availability 总被引:2,自引:0,他引:2
To examine responses of a plant species to nutrient availability, we investigated changes in soil nutrient availability, litterfall
production and nutrient content in litterfall along a topographic gradient in aPinus thunbergii Parl. plantation. Responses were evaluated in terms of three efficiency indices: (i) nutrient-uptake efficiency (the ratio
of nutrient return in litterfall to soil nutrient availability); (ii) nutrient-use efficiency (the ratio of litterfall mass
to nutrient return in litterfall); and (iii) nutrient-response efficiency (the ratio of litterfall mass to soil nutrient availability).
These indices can distinguish the ability of a species to acquire nutrients and its ability to use them in litterfall production.
Nitrogen and phosphorus availabilities in soil were lower in upper slope positions. The three efficiencies were higher in
upper slope positions and negatively correlated with soil nutrient availability for both nitrogen and phosphorus. An increase
in nutrient-response efficiency was achieved by both increases in nutrient-uptake and nutrient-use efficiencies. 相似文献
173.
The reproductive allocation (allocation of net production to acorns) of a tall tree speciesQuercus serrata was estimated by a method combining branch diameter distribution and the sampling of acorns per branch. Acorn production
per branch of 0.5-cm diameter significantly varied among individuals and years, but not significantly across tree size. Leaf
production per branch of 0.5-cm diameter had little annual fluctuation, while that of acorns fluctuated about 6 times between
the maximum and minimum. The reproductive allocation was regressed against vegetative allocation, following the general model
of klinkhameret al. (1992); the reproduction had a beginning threshold and reproductive allocation increased drastically at relatively young
stage after the tree began reproduction. With its small threshold production, coppicing traits and large maximum size,Q. serrata seemed adaptive to infrequent but large-scale disturbances like fires. 相似文献
174.
Etienne Jean Faye Kazuhiro Kogame Satoshi Shimada Shigeo Kawaguchi Michio Masuda 《Phycological Research》2007,55(2):150-158
Vegetative and reproductive structures of the little‐known red alga, Meristotheca coacta Okamura (Solieriaceae, Gigartinales) were described on the basis of specimens collected from three localities in southern Japan, including an island close to the lectotype locality. Meristotheca coacta was shown to be a strongly supported monophyletic clade in our rbcL analyses. The taxonomic features of this species were reassessed. This species is characterized as follows: (i) the thalli consist of relatively thick (300–1400 μm from the uppermost to basal regions), elastic and rose‐red blades; (ii) the blades are irregularly lobed and branched into variously shaped segments with undulate and crispate margins; (iii) tetrasporangial initials are laterally attached to their parental cells and the lateral pit‐connections remain in mature tetrasporangia; (iv) gametophytes are dioecious; (v) carpogonial branches are three‐celled (occasionally two‐ or four‐celled); (vi) a darkly staining auxiliary cell complex is present and recognizable prior to diploidization; and (vii) cystocarps are produced along (or near) the margins of the blades and on the marginal proliferations and lack spinous outgrowths. 相似文献
175.
The potentiometric titration curves of carboxymethylcellulose, which has a relatively stiff backbone, and also of poly(D -glutamic acid) in the helical region are compared with the theoretical curves calculated assuming that the polyions are rods and have smeared charges on their surfaces. For carboxymethylcellulose good agreement is observed when its charge density is high, whereas as the charge density decreases the calculated curves deviate from the observed ones. The main reason for the disagreement at low charge densities may be attributed to the flexibility of the polymer backbone. For helical poly(D -glutamic acid) satisfactory agreement between calculated and observed curves is found if a radius thicker than the realistic radius is employed. The reason for the excessively large radius may be attributed to the inapplicability of the smeared charge model. 相似文献
176.
It has been shown that the cultured cells of Digitalis purpruea are capable of transforming progesterone (I) to 5α-pregnane-3,20-dione (II), 5α-pregnan-3β-ol-20-one (III), its glucoside (IV), 5α-pregnane-3β,20α-diol (V), its glucoside (VI), 5α-pregnane-3β,20β-diol (VII), its glucoside (VIII), Δ4-pregnen-20α-ol-3-one (IX), its glucoside (X), Δ-pregnen-20β-ol-3-one (XI) and its glucoside (XII). 5α-Pregnan-3β-ol-20-one glucoside (IV), 5α-pregnane-3β,20α-diol glucoside (VI), 5α-pregnane-3β,20β-diol glucoside (VIII), Δ4-pregnen-20α-ol-3-one glucoside (X) and Δ4-pregnen-20β-ol-3-one glucoside (XII) have been found for the first time as new metabolises by plant tissue cultures. A scheme for the biotransformation of progesterone (I) has been proposed, and the reduction and glucosidation activities distinctly have been observed in these cultured cells. 相似文献
177.
The effect of photosynthetically active radiation and temperature on the photosynthesis of two Vietnamese species of Sargassum,S. mcclurei and S. oligocystum,based on the field and laboratory measurements
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Ryuta Terada Triet D. Vo Gregory N. Nishihara Kazuya Matsumoto Shogo Kokubu Yuki Watanabe Shigeo Kawaguchi 《Phycological Research》2016,64(4):230-240
SUMMARY The effects of photosynthetically active radiation (PAR) and temperature on the photosynthesis of two Vietnamese brown algae, Sargassum mcclurei and S. oligocystum (Fucales), were determined by field and laboratory measurements. Dissolved oxygen sensors and pulse‐amplitude modulated (PAM) fluorometry were used for the measurements of photosynthetic efficiency. A Diving‐PAM revealed that underwater measurements of the effective quantum yield (Φ PSII ) of both species declined with increasing incident PAR, with minimum Φ PSII occurring during noon to early afternoon. Φ PSII recovered in the evening, indicating photo‐adaptation to excessive PAR. In laboratory experiments, Φ PSII also decreased under continuous exposure to 1000 μmol photons m?2 s?1; and full recovery occurred after 12 h of dark acclimatization. The net photosynthesis – PAR experiments of S. mcclurei and S. oligocystum conducted at 28°C revealed that the net photosynthetic rate quickly increased at PAR below the saturation irradiance of 361 and 301 μmol photons m?2 s?1 and nearly saturated to maximum net photosynthetic rates of 385 and 292 μg O2 gww ? 1 min?1 without photoinhibition, respectively. Gross photosynthesis and dark respiration experiments determined over a range of temperatures (12–40°C), revealed that the maximum gross photosynthetic rates of 201 and 147 μg O2 gww ? 1 min?1 occurred at 32.9 and 30.7°C for S. mcclurei and S. oligocystum, respectively. The dark respiration rates increased exponentially over the temperature ranges examined. The estimated maximum value of the maximum quantum yield occurred at 19.3 and 20.0°C and was 0.76 and 0.74, respectively. Similar to the natural habitat of the study site, these two species tolerated the relatively high temperatures and broad range of PAR. The ability of these species to recover from exposure to high PAR is one of the mechanisms that allow them to flourish in the shallow water environment. 相似文献
178.
179.
K Yamada K Yamakawa Y Terada K Kawaguchi A Sugaya T Sugiyama N Toyoda 《Hormones et métabolisme》1999,31(9):508-513
Depletion of GLUT4, the primary glucose transporter protein in adipose tissue and skeletal muscle, is reported to contribute to insulin resistance in pregnancy or diabetes. To examine this phenomenon, the expression of GLUT4 protein was assessed by Western blotting in streptozotocin-induced diabetic pregnant rats. In adipose tissue, relative to control, it was decreased by 30% in the normal pregnant group (p<0.001), by 37% in the diabetic nonpregnant group (p<0.01) and by 65% in the diabetic pregnant group (p<0.001). On the other hand, no significant variation was evident among the groups in skeletal muscle. To assess the mechanisms responsible for depletion of GLUT4 protein in adipose tissue, we quantitated levels of GLUT4 mRNA with a RNase protection assay. It was decreased by 44% in the normal pregnant group (p<0.05) and by 55% in the diabetic pregnant group (p<0.05), but not altered in the diabetic nonpregnant group. These results suggest that the depletion of GLUT4 protein in adipose tissue is a factor contributing to insulin resistance in pregnancy or diabetes, especially when the two states exist in combination. 相似文献
180.
N Nakagawa H Yasuda K Yano S i Mochizuki N Kobayashi H Fujimoto N Shima T Morinaga D Chikazu H Kawaguchi K Higashio 《Biochemical and biophysical research communications》1999,265(1):158-163
Basic fibroblast growth factor (bFGF) induced osteoclast formation in co-cultures of mouse spleen cells and osteoblasts. Osteoclastogenesis inhibitory factor (OCIF) and a selective cyclooxygenase-2 (COX-2) inhibitor, NS-398, abolished bFGF-induced osteoclast formation. bFGF did not affect spleen cells, but it did affect osteoblasts, to stimulate osteoclast formation. Northern blot analysis revealed that bFGF up-regulated the expression of osteoclast differentiation factor (ODF) and COX-2 and down-regulated the expression of OCIF in primary osteoblastic cells. NS-398 abolished the increase of ODF mRNA, but it had no effect on the decrease of OCIF mRNA. NS-398 suppressed the binding of (125)I-labeled OCIF to osteoblastic cells treated with bFGF. Enzyme-linked immunosorbent assay showed that bFGF inhibited OCIF production by osteoblastic cells, and the inhibition was not affected by NS-398. We conclude that bFGF induces osteoclast formation by stimulating ODF production through COX-2-mediated prostaglandin synthesis and by suppressing OCIF production through a mechanism independent of prostaglandin synthesis. 相似文献