摘要:

Using a macrophotographic technique, kinetic studies were performed on growth and gravireaction, both measured on maize (cv. LG 11) roots. When using intact roots, it was found that the growth rate decreased two hours after the beginning of the gravistimulus, the rate of root curvature being optimal at that time. These two processes are greater in light than in the dark. Subsequently, the curvature rate decreased rapidly to zero in the dark but, in light, it continued for at least a further three hours. There was then a recovery of elongation in darkness whereas in light growth rate remained low. A comparative analysis between root segments and intact roots suggests that the correlation between the growth and the gravireaction rates differs according to the system studied and that light has a greater effect on growth rate when the roots are subject to gravitational stimuli. Present data are discussed in terms of hormone balance between several endogenous regulators.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1982.tb00568.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Net photosynthesis of current and one‐year‐old shoots in Scots pine (Pinus sylvestrisL.) was measured during a two‐year period (1977–1978). The measurements were carried out in Central Sweden using a system that allowed in situ measurements throughout the year. The photosynthetically active period, defined as months with a positive carbon dioxide balance, was nine months per year for one‐year‐old shoots and six months for current shoots. The daily rates of net photosynthesis were low in spring and late autumn and 95% of the annual photosynthetic production occurred from May to October. In spring net photosynthesis was limited by a low photosynthetic capacity and a restricted access to water caused by the frozen ground. It took more than three months in spring and early summer to restore full photosynthetic capacity in the one‐year‐old shoots, but the rate of recovery varied considerably between the two years. In late autumn the rates of photosynthesis were mainly limited by low photon flux densities.The seasonal patterns of photosynthesis were similar between the two years, and even though there were pronounced differences for individual months, the total annual photosynthetic production of the two years only differed by 1.4% for the one‐year‐old shoots. The differences in photosynthetic production for current shoots were much higher as an effect of different rates of needle development and differences in photosynthetic capacity during the two years. An estimate of the carbon balance of the current shoots showed that the shoots had not photosynthesized their own weight in terms of carbon until late August (1978) or early September (1977), which means that their photosynthetic production was of minor importance for the for

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1982.tb00569.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The rates of net photosynthesis and transpiration of one‐year‐old shoots were measured in situ in five different positions within the crown of a young Scots pine (Pinus sylvestrisL.). Measurements were carried out on south‐ and north‐facing shoots on the third and sixth whorls, respectively, and on an east‐facing shoot on the ninth whorl. In another investigation the rates of gas exchange of one‐year‐old shoots on the third whorl of eight different trees were studied. The measurements were made during June and July, 1977, under non‐limiting conditions of soil water. The daily rates of net photosynthesis in whorls three and six followed the light conditions closely, with higher rates for the south side of each whorl and higher for whorl three than six. On whorl nine the shoot had a higher light compensation point and a low rate of photosynthesis at light saturation compared to the other shoot positions. The quantum yield for the shoot on the lowest whorl, as estimated from the linear part of the light response curve, was 50% lower than for shoots on whorl three and six.The variation in transpiration rates was pronounced within the crown as an effect of differences in the absolute value and diurnal course of stomatal conductance. The variation in net photosynthesis was small between different trees while the variation in transpiration was much higher. Thus the variation in water use efficiency was great. It is concluded that it is possible to extrapolate measurements of net photosynthesis from individual trees up to a stand level without introducing large errors in the estimate. More caution must be paid before extrapolating tree transpiration up to stand transpiration. However, before an extrapolation of gas exchange is made from tree to stand level the variation in net photosynthesis and transpiration rate within the crow

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1982.tb00570.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Anthers of different species of the generaAnemone, Clematis, PapaverandNicotianawere cultured by floating on a liquid medium which overlay an agarified charcoalmedium. This technique proved to be superior to conventional methods i.e. culture on either solid or liquid media. Cold treatment ofAnemoneanthers for 7 days after inoculation on the double layer medium gave about the same frequency of embryos per anther as corresponding cultures cold treated before inoculation. An elevation of the CO2concentration to 2% stimulated embryogenesis in anther cultures ofAnemone canadensis, Anemone vitifolia, Papaver setigerumandPapaver radicatum. Cold treatment of cultures ofAnemone canadensisinhibited embryogenesis if the ensuing culture was performed in 2% CO2.On the other hand, cold treatment was stimulating, with an optimum of about 20 days, if the cultures were maintained in normal air. Chemical analysis of untreated anthers ofAnemone canadensisshowed the presence of abscisic acid (2.2 × 10−6g/g anthers). Cold treatment reduced the concentration of abscisic acid to 0.6 × 10−6g/g anthers. By use of assays withLemna gibbaas test organism, activated charcoal was shown to adsorb abscisic acid that was added to the medium. Medium treated with charcoal before inoculation of anthers ofAnemone canadensisprovided to inhibit embryo produ

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1982.tb00571.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The influence of prolonged dark periods on the concentration of pinitol in white clover (Trifolium repensL. ev. Regal Ladino) and soybean [Glycine max(L.) Merr.] tissue was investigated. Clover and soybean plants were harvested periodically throughout continuous dark periods of 40 and 44 h, respectively, followed by 24 h of continuous light. The foliage and root tissue of clover and foliage tissue of soybeans were analyzed for the concentration of glucose, fructose, sucrose and pinitol. Pinitol concentration (mg/g dry weight tissue) was unchanged by the prolonged dark period followed by 24 h of continuous light compared to tissue of plants harvested at 0‐h and plants receiving normal photoperiods. Concentrations of the carbohydrates, in the tissue were depleted by the prolonged dark period. However after 6 h of light, the concentration of these sugars increased to concentrations equal to 0‐h harvested plant tissue and tissue of plants receiving normal photoperiods. These results indicate that pinitol probably does not function as a source of reserve energy comparable to sucrose, glucose, and fruct

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1982.tb00572.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The absorption and translocation of diclofop‐methyl (methyl 2‐[4(2′,4′‐dichlorophenoxy)phenoxy]propanoate) was examined by using a specially designed treatment apparatus that separated excised roots or roots of seedlings into four zones. [14C]‐Diclofop‐methyl was absorbed along the entire root length of both wheat (Triticum aestivumL.) and oat (Avena sativaL.). In both species, absorption was greatest in the apical region of the root. Absorption by the apical region of wheat roots was more than three times greater than the basal portions, and more than twice as great as the apical region of oat roots. Less than 5% of the absorbed diclofop‐methyl was translocated in both wheat and oat roots. Diclofop‐methyl and diclofop(2‐[4(2′,4′‐dichlorophenoxy)phenoxy]propanoic acid) were the predominant translocated forms. The absorption and translocation of amitrole (3‐amino‐1,2,4‐triazole) were also examined. Amitrole was absorbed along the entire length of wheat roots and translocated primatily in the basipetal direction. The usefulness of the specially designed apparatus for biochemical and phy

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1982.tb00573.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The chromatin was isolated from embryos or young seedlings of wheat,Triticum aestivumL. cv. Mukakomugi, and the template activity, the endogenous RNA polymerase activity, the susceptibility to DNase 11 and polylysine binding capacity were assayed. Both transcriptional activities of chromatin were very low for the first 12 h of germination, increased from 12 to 24 h, and then increased markedly during the next 48 h of post‐germination. During the 72 h of germination, the template activity and the endogenous RNA polymerase activity increased 10‐fold and 40‐fold, respectively, while they decreased from 72 h to 96 h of seedling growth. Seventy‐two h seedling chromatin was more susceptible to endonuclease and was bound with more polylysine than the germ chromatin. These results suggest that the structure of the chromatin available for transcription changes during seed germination and seedling

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1982.tb00574.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

In the unicellular algaCyanidium caldariumnitrate utilization is strongly inhibited by ammonium and it is resumed when ammonium has been depleted. In the presence of L‐methionine‐DL‐sulphoximine (MSX), which prevents ammonium assimilation through a specific irreversible inhibition of glutamine synthetase, nitrate reduction is no longer inhibited by ammonium, and most of the ammonium derived from nitrate reduction is excreted into the external medium. However, in the presence of MSX, nitrate reduction to ammonium proceeds at a reduced rate (45 to 70% of the control); this is particularly marked at low nitrate concentration. It is hypothesized that either MSX or accumulating ammonium bring about decrease in the rate of nitrate entry into the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1982.tb00575.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

During the first 96 h of culture, germinating spores of the fernSphaeropteris cooperi(F. v. Muell.) Tryon showed a gradual rise in respiratory activity to a maximum of about 6.5 μl 02h−1mg−1dry wt. This was followed by a transitory decline in rate, concluded by a second respiratory rise preceding the emergence of the rhizoid after 192 h of culture. Oxygen uptake during the first 120 h of germination was insensitive to 1 mMpotassium cyanide (KCN) but was inhibited by 1 mMsalicylhydroxamic acid (SHAM); however, beyond this time cyanide showed increasing inhibitory effectiveness whereas SHAM became less effective. Regardless of time of application, KCN had no effect on germination. Maximum inhibition of germination by SHAM was achieved if applied up to 120 h after culture initiation, after which spores became insensitive to SHAM. Heat treatment (50°C for 90 min) during the cyanide‐resistant phase of respiration (0 h–120 h) induced cyanide‐sensitive respiration and completely inhibited spore germination. Elevated temperatures had little effect if applied during the cyanide‐sensitive phase (beyond 120 h). Temperature inhibited spores regained their ability to germinate if maintained in culture until the cyanide‐resistant pathway was restored and then subjected to a second photoinductive light treatment. These results suggest the presence and possible involvement of the cyanide‐resistant, alternative respiratory pathway during germination ofSphaeropte

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1982.tb00576.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The spores of the fernAnemia phyllitidiscontain abundant quantities of lipid as reserve material. Germination of these spores can be induced either by red light or, even in the dark, by gibberellic acid. The effects of both these factors on lipid degradation, lipase and isocitrate lyase activities, and on the fatty acid composition have been studied in the course of the germination process. During germination in darkness with gibberellic acid, the fatty acid composition remained similar to that in the ungerminated spore. In contrast, when spores were germinated in red light, α‐linolenic acid was synthesized. Little activity of lipase and isocitrate lyase could be detected in the dry spore. Red light or gibberellic acid affected a dramatic increase of the activities of these enzymes. Lipid breakdown and lipase activity were more active in red light, however. Permanent stimuli were necessary for growth and complete lipid degradation. Induction of germination simultaneously with both factors revealed an additivity of the effects of red light and gibberellic ac

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1982.tb00577.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY