摘要:

In vitrostudies of germinatingLilium longiflorumpollen showed that starch increased more rapidly during the first 30 minutes of incubation than during the next several hours. The period of rapid starch formation coincided with the first period of high respiration. An estimate was made of the extra ATP utilized to form extra starch during the first 30 minutes, and this estimate indicates that starch synthesis accounts for a significant portion of the initial high rate of respiration. This pattern of respiration and starch synthesis was not altered when pollen germinated in a pentaerythritol medium that could not be metabolized instead of the standard sucrose medium.Sucrose was the predominant sugar in mature lily pollen. This sugar decreased 50% during several hours incubation in pentaerythritol culture medium. Reducing sugars remained low during incubation which may indicate that sucrose breakdown is regulated by the rate of utilization of hexose units.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1968

数据来源: ASPB

摘要:

The application of gibberellin toAcer negundoeither during or after a short photoperiod strikingly lowered the amount of hardiness obtained after 4 weeks in darkness at 5°. Two growth retardants, B9 and Amo 1618, the latter of which interferes with gibberellin synthesis, brought about hardiness increases under long photoperiods. The naturally occurring inhibitor, dormin, also increased hardiness under the usual inhibiting influence of long photo-periods. Extracts from plants given long or short days had gibberellin-like compounds in largest quantities during LD and lowest quantities under SD, while the inverse was true for the inhibitor

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1968

数据来源: ASPB

摘要:

Absorption of selenate and selenite by excised roots ofAstragalus Crotalariae, a selenium accumulator, and ofA. lentiginosus, a non-accumulator, was favored by CaCl2and a pH of 4.0. The uptake of selenate and possibly selenite, is metabolically linked. Roots of a number ofAstragalusspecies were examined, and in all cases selenate entered the roots much faster than selenite. In these short-term experiments there was no relation between uptake of the 2 ions and classification of a species as selenium-accumulator or non-accumulator.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1968

数据来源: ASPB

摘要:

Helminthosporium victoriaetoxin, which affects only hosts of the toxin-producing fungus, causes loss of electrolytes from roots, leaves, and coleoptiles of treated plants. Root hair cells lost the ability to plasmolyze after 20 minutes exposure to toxin in solution; comparable resistant cells retained plasmolytic ability during 3 hours exposure. Toxin stopped uptake of exogenous amino acids and Pi by susceptible but not by resistant tissue. Incorporation of32P into organic-P and14C-amino acids into protein was blocked in susceptible but not in resistant tissue. Apparent free space increased in susceptible but not in resistant roots. The increase was evident within 30 minutes, and reached 80% free space after 2 hours exposure to toxin. When cell wall-free protoplasts were exposed to 0.16μg toxin/ml, protoplasmic streaming stopped and all plasma membranes of susceptible protoplasts broke within 1 hour. Resistant protoplasts were not affected significantly. Data support the hypothesis of a primary lesion of toxin in the plasma membrane. Effects on synthesis could result from lack of transport of exogenous solutes to sites of synthesis. It is possible that all other observed effects of toxin are secondary to membrane damage

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1968

数据来源: ASPB

摘要:

Gibberellic acid (GA3) induces invertase activity within 6 hours inAvenastem segments that are incubated in the dark at 23°. The maximum amount of promotion is about 5 times that of invertase activity in untreated segments. GA3causes significant promotion of invertase activity at concentrations as low as 3×10−5μmGA3. The increase in invertase activity elicited by GA3between 3×10−5μmand 300μmclosely parallels the growth promotion that is caused by GA3over this concentration range. In control segments, invertase activity rises steeply during the first 6 hours of incubation, then decays slowly between 12 and 48 hours. In GA3-treated segments, the invertase activity also rises during the first 6 hours, parallel to that in control segments and continues to rise during the next 42 hours. These changes in invertase activity during 48-hour incubation periods do not parallel the changes in growth that occur in control and GA3-treated segments. Cycloheximide at 10μg/ml abolishes all GA3-promoted growth and invertase activity in these segments. Actinomycin D at 40 and 80μg/ml decreases GA3-promoted growth by 20% and invertase activity by 38 and 44%, respectively. The data clearly support the idea that protein synthesis is necessary for GA3-promoted growth and invertase activity inAvenast

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1968

数据来源: ASPB

摘要:

The action of prolonged far-red on seed germination was studied inLactuca sativaL. var. Grand Rapids. Exposure of imbibed seeds to 6 hours far-red before the application of gibberellic acid (GA3) and thiourea completely prevented germination. Using GA3, this far-red was effective after the sixth hour of imbibition. At 6, 12, and 18 hours of imbibition equal durations of far-red had equal effects. The kinetics of far-red action was investigated: it was found that although far-red for several hours, irrespective of the energy level, was needed for maximum inhibition, shorter durations (15 and 30 mins) were also appreciably effective provided they were followed by several hours darkness before the supply of GA3. This is taken to indicate the existence of labile product(s) of the action of a far-red sensitive pigment. Evidence is provided for the existence of promotive dark processes controlled by this pigment, which are essential for germination whether triggered by GA3, thiourea or red-light. A model for the operation of the pigment system is proposed and its role in the germination mechanism of this seed is discussed.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1968

数据来源: ASPB

摘要:

A method is described for the extraction and measurement of soluble nucleotides from wheat grain. Nucleotides were separated (80-90% recovery) by paper chromatography followed by electrophoresis. The nucleotides extracted were ADP-glucose, ATP, ADP, AMP, and NAD; UDP-glucose, UTP, UDP, and UMP with smaller quantities of cytidine nucleotides.In grain sampled at 20 days after anthesis, 70% of the UDP-glucose was present in the endosperm and the remainder in the testa and pericarp; 90% of the ADP-glucose was found in the endosperm. Of the four uridine nucleotides UDP-glucose was the most plentiful and the level rose from about 330 mμmoles per g fresh weight on the third day after flowering to 430 mμmoles/g on day 12 and then fell steadily to about 140 mμmoles/g just before complete ripening. Levels of 250 mμmoles and 200 mμmoles per g fresh weight were recorded for UTP and UDP on day 12. Thereafter the content of UTP fell relatively more rapidly than either UDP or UDP-glucose.ATP was the most abundant adenine nucleotide and from 7 days after anthesis to day 40 the quantity per g fresh weight fell from about 350 mμmoles to 100 mμmoles. The level of ADP-glucose rose to a maximum of 140 mμmoles/g between days 15 and 21 and then fell slightly towards maturity while ADP varied between 50 and 80 mμmoles/g. On day 20, coinciding with the maximum rate of starch synthesis in the endosperm, the concentration of ADP-glucose in this tissue was about 0.3 mm, and that of UDP-glucose 0.7 mm.The relationship of these results to the mechanism of transfer of hexose units from sucrose to starch is d

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1968

数据来源: ASPB

摘要:

The present study reports on chemical changes which occur in the cell wall ofZea maysduring early phases of growth. Roots of seedling corn plants were divided into a meristematic zone, the zone of elongation, and the maturation zone, and the cell wall isolated from each of these zones. The wall preparations were then extracted sequentially to obtain pectin, hemicellulose, cellulose, and lignin fractions. Each of these, except for the lignin fraction, was hydrolyzed and the resultant sugars isolated, identified, and estimated quantitatively. Quantitative analysis of the products of hydrolysis of these fractions demonstrated that the classical scheme of fractionation is a valuable indicator of the changes in solubility properties which the various polysaccharide components for the wall undergo. It does not however yield definite chemical entities. For example, the“pectin”fraction contains only about 3% galacturonic acid; the bulk of it being composed of glucose, xylose, and galactose. By summation of analysis of these various fractions, it was found that substances yielding glucose and xylose upon hydrolysis increase with advancing age of the tissue. Galactose- and arabinose-yielding compounds decrease and mannose appears during maturation. Anhydrouronic acids first decrease, then increase. Most interestingly, of the total dry weight of the cell wall, only 24, 45, and 50% of the meristematic, elongation, and maturation zones respectively are accounted for as simple sugars in the acid hydrolysates. Oligosaccharides were not encountered in large amounts so that the 50 to 75% of the wall weight unaccounted for would consist of polysaccharides or oligosaccharides not precipitated by ethanol from the extracting solutions employed and by polysaccharides in the hemicellulose fraction which are resistant to acid hydroly

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1968

数据来源: ASPB

摘要:

Sugar cane, an intermediate day plant, clearly received a stronger stimulus to flower during lengthening nights than during shortening nights. Flowering was vigorous under warm, lengthening nights (21°) but less so under cool, lengthening nights (16-17°). Warm or cool shortening nights either failed to induce flowering altogether or reduced it substantially. Under the warmer nights the inductive dark period was 10 hours 57 minutes to 11 hours 26 minutes whether the nights were lengthening or shortening. Under cooler conditions, it was longer by from 20 minutes to nearly 2 hour

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1968

数据来源: ASPB

摘要:

Crested wheatgrass seeds [Agropyron desertorum(Fisch. ex Link) Schult.] were tested for their ability to carry on phosphorylation reactions at low water potentials. Seeds were treated with32P labeled sodium phosphate and incubated in air having different controlled relative humidities. Ion exchange chromatography and radioassay of phosphate esters indicated that some phosphorylation occurred at a water potential of−880 atmospheres. Seeds did not incorporate32P in nicotinamide adenine dinucleotide, adenosine triphosphate, and uridine diphosphate hexose until they were moistened to a water potential of−130 atmosphe

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1968

数据来源: ASPB