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1.
Effects of Cl and other anions on the rate of HILL reactionin Euglena chloroplasts were investigated. Cl acceleratedthe reaction rate with ferricyanide as HILL oxidant; Br,F and I were also effective; NO3, PO42–and SO42– were less effective. Divalent cations, Ca2+and Mg2+, were also highly effective. The promoting effectsof these ions were highly dependent on pH and the nature andconcentration of the HILL oxidant used. Accelerating effectsof the ion increased with decreasing concentrations of ferricyanide.Generally, the stimulating effect of Cl was much moremarked at pH 7–7.5, with little effect at pH 5. Thus,the pH-activity relationship in the HILL reaction is more orless markedly modified by addition of ions. Cl, and other anions, accelerated the reaction by affectingonly the dark rate-limiting portion of the HILL reaction; thelight reaction constant remained uninfluenced. We inferred thatsome reaction step, at which ferricyanide receives electronfrom photosystem 2, is accelerated by Cl and other ions.Cl effects were rather small, or undetectable, with DPIPor p-benzoquinone as oxidants. (Received January 8, 1970; )  相似文献   
2.
Decrease of dry material, water, potassium and divalent cationsin the cotyledon (catabolic organ and accumulation of thesesubstances in the seedling (anabolic organ) were traced duringthe germination stage of Vigna sesquipedalis, cultured at 15°,25° and 30° in the dark on the sand with the supplyof tap water. One half of the divalent cations finally accumulatedin the seedling came from the root, whereas most of the potassiumfrom the cotyledon. Practically all the calcium in the cotyledonremained untransported, while 90% of K stored in the cotyledonwas transported into seedling. As for divalent cations otherthan Ca, 50–60% of the total divalent cations was transportable.The concentration of K, transportable dry material and transportabledivalent cations decreased linearly with the culture age. Fromthe temperature dependency of the rate of this decrease, itwas inferred that the transport of cations from cotyledon toseedling involved at least two component processes having activationenergies of approximately 5 and 16 Kcal, respectively. The rateof transport at 30° was found to be 10–20 times greaterthan that calculated from the simple diffusion model in water.Fractionation of cell inclusions in the cotyledon by the useof a centrifuge (1,500 and 16,000 rpm) suggested that the amountsof ions in the precipitable fractions, being bound to certaincell components, precisely corresponded to the untransportablefraction. 1Main part of this work was reported at the Annual Meeting ofthe Botanical Society of Japan held at Fukuoka on Oct. 25. 1958. (Received October 16, 1961; )  相似文献   
3.
A new method in growth-electrophysiology: Pressurized intra-organ perfusion   总被引:7,自引:7,他引:0  
Abstract A new experimental system was devised for the simultaneous measurement of elongation rate and the activity of the spatially separate electrogenic ion pumps of a hypocotyl segment excised from a seedling of Vigna unguiculata L. Walp. under enforced intra-organ perfusion by artificial solutions. The pathway of the perfusion medium was apoplastic space, including xylem vessels as main routes. The elongation rate of the segment was highly dependent on the perfusion pressure applied. It was possible to increase the growth rate under pressurized perfusion by 10-30 times as much as that without perfusion. Elongation rate was also dependent on respiration under perfusion, being retarded reversibly by anoxia a few minutes after the activities of the electrogenic ion pumps were stopped. Perfusion pressure had a little influence on the membrane potential (Vpx) below a breakdown level (c. 130 kPa). Perfusion of mannitol or sorbitol solution of appropriate concentration reduced the elongation rate reversibly.  相似文献   
4.
'METACHRONOUS' CLEAVAGE AND INITIATION OF GASTRULATION IN AMPHIBIAN EMBRYOS   总被引:1,自引:1,他引:0  
The cleavage pattern in the egg of Xenopus laevis has been investigated with the aid of time-lapse cinematography. From the 5th cleavage onward, divisions of the surface blastomeres are not synchronous but metachronous. A few blastomeres in a very restricted region which is situated in most cases in the dorsal side of the animal hemisphere, slightly distant from the median line and near the equatorial junction of the animal and vegetal hemispheres, divide before the other blastomeres, and a wave-like propagation of the divisions travels along the surface from that region toward the animal and vegetal poles. The wave-like propagation ends in the vegetal pole region. In the animal hemisphere, this pattern of cleavage is continued until the 13th cleavage and thereafter the divisions of surface blastomeres become asynchronous. In the vegetal pole region, however, the 14th metachronous division of blastomeres is clearly observed in the film. Gastrulation begins after 14 cleavages.  相似文献   
5.
Protein Synthesis in Dormant and Non-Dormant Cocklebur Seed Segments   总被引:1,自引:0,他引:1  
Using the axial and cotyledonary segments of lower cocklebur (Xanthium pensylvanicum Wallr.) seeds, protein synthesis as shown by incorporation of radioactive leucine was examined in relation to their dormant status. During the first 9 h of water imbibition, the protein synthesis was higher in the dormant axes than in the non-dormant, after- ripened ones. When imbibed for more than 12 h non-dormant axes had a higher activity than dormant ones. This was also the case with the cotyledonary segments. Cyctoheximide, an inhibitor of protein synthesis, blocked protein synthesis in the axial tissue regardless of its dormant status, and thereby inhibited germination of the non-dormant seeds. In the dormant seeds, however, cycloheximide at 3 mM slightly stimulated germination without stimulating the C2H4 production. Based on these results, it is suggested that in cocklebur seeds there may be some proteinaceous system which is involved in the maintenance of dormancy.  相似文献   
6.
Physiological responses to decapitation, in combination with bud removal or bud retention, were followed for 45 days in mature leaves of potted mulberry trees (single shoot with 24 to 28 leaves) held in a greenhouse. Mature leaves, whose photosynthetic activity had already attained a maximum, initially increased and subsequently maintained their rates of gas exchange after decapitation. Equivalent leaves on intact trees showed a gradual decline in photosynthesis together with other changes generally associated with early senescence viz. loss of chlorophyll, increased starch, and accumulation of one category of cytokinin-like material presumed to be a glucose ester. Maintenance of physiological activity following decapitation, especially when combined with bud removal, was associated with greater chlorophyll content, mesophyll cell enlargement (palisade cells appeared more elongate), lower starch, and alteration in foliar levels of cytokinin-like substances. Internal constraints on CO2 assimilation, i.e. residual resistance (rr), rather than stomatal factors, appeared to be the major influence on gas exchange. The higher photosynthetic activity of leaves on decapitated trees relative to control trees of the same age was attributed to lower r, but was also associated with higher chlorophyll content (leaf area basis) so that CO2 assimilated per unit chlorophyll was not substantially altered by treatment.  相似文献   
7.
The role of the oxidative pentose phosphate (PP) pathway in the dormancy-breaking of cocklebur (Xanthium pennsylvanicum Wallr.) seeds was investigated. D-[1-14C]-glucose or D-[6-14C]-glucose was fed to dormant and non-dormant lower seeds or to their axial or cotyledonary segments which were imbibed for different durations, and C6/C1 ratios of respired 14CO2 as an index of the PP pathway activity were calculated. Contrary to expectation, there was no significant difference in the C6/C1 ratios between the dormant and non-dormant seeds or segments during a water imbition period of 24 h, although the PP pathway actually operated already in an early stage of water imbibition. Also concerning the activities of G6PDH and 6PGDH, the key enzymes of this pathway, no difference between the dormant and non-dormant seeds was found. It was thus concluded that, unlike other seeds, there is no contribution of the PP pathway to the regulation of dormancy of the cocklebur seed.  相似文献   
8.
SYNOPSIS Interacellular membrane potential and spontaneous changes associated with motile responses in the zooid of Vorticella convallaria Linnaeus were recorded by conventional electrophysiological technics. an all-or-none large transient depolarization (large pulse) occurs in association with a spontaneous contraction of the zooid. A small transient potential change (small pulse) was observed in association with periodic contraction of the contractile vacuole.  相似文献   
9.
10.
Overall concentration of free inorganic ions distributes inthe hypocotyl of a bean seedling {Vigna sesquipedalis) at aconstant level (H+) or decreases monotonously from the cotyledonarynode towards the base (K+, Na+, Ca++ and Mg++, phosphate, NO3).According to our theory, this is inconsistent with the distributionof electric potential having a definite minimum in the elongatingregion. The discrepancy can not be explained by regional variancein radial potential difference or histological differentiationin passive ionic permeability of the cell membrane. Short circuitcurrent observed through a hypocotyl segment corresponded toa net flux in ions of 10–24 pEq/cm2.sec. It is questionable,however, whether this is due to active ion transport, whichcan be the source of electric potential difference, or is apassive flow due to histological heterogeneity in ion concentration. In order to investigate the latter possibility, pH of sap exudingfrom stumps made at various intervals along the hypocotyl axiswas measured, since H+ is the ion electro-osmotically most effective.pH Values of acropetal exudates distributed along the axis closelycorresponding to the distribution of electric potential. Thissuggests that potential distribution is determined by a passiveflow of H+ through a specific channel in the vascular system.The fact that H+ production and the uptake of ions and waterare most active at the elongating zone of hypocotyl is discussedfrom a physiological point of view. (Received December 3, 1969; )  相似文献   
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