摘要:

AbstractThe turions ofPotamogeton crispusL. develop in early summer and function in propagation and dispersal. Under natural conditions during longday periods, an average minimum air temperature of more than 12°C was found to be important for turion formation. Experiments with controlled environments indicate that both temperature and photoperiod regulate turion formation. Turions can be induced at 13°C or above but not at 8 or 10°C. At a temperature range of 13–24°C turions form in both 12‐ and 16‐h days, but not in 8‐h days. By increasing temperature from 24 to 30 or 35°C turions can be induced under 8‐h days. Light intensity was found to be important in the format

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb02660.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThe formation of lysigenous cavities (aerenchyma) in the root cortex of maize,Zea maysL. cv. Capella, under well‐aerated conditions has been studied in relation to the composition of the nutrient solutions. Nitrogen, either supplied as nitrate or as ammonium, reduced the cavity formation by the roots. This reduction was most apparent at nitrate concentrations above 2 mM. Cavities were increasingly formed when the nitrate concentration was decreased and they reached their largest dimensions in roots growing in water. Thus, inadequate availability of nitrogen leads, under acrated conditions, to deterioration of cortex cells and cavity formation in the maize roots. It is suggested that cavity formation in these roots is connected with reduced nitrogen assimilatio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb02661.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractSugarcane (Saccharumspp. hybrids) plants were exogenously supplied with, 0, 1.0, 1.5, and 2.0 mg gibberellic acid (GA3) per stalk in single and multiple applications. Increases in stalk fresh weight, total stalk length, and lengths of individual internodes were primarily a function of the interval between applications. Applications produced additive growth responses at 15‐ and 30‐day intervals but not at 0‐ and 45‐day in

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb02662.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractLettuce seeds (Lactuca sativaL. cv. Grand Rapids) imbibed in darkness at supra‐optimal temperatures (23 ± 1°C) develop a secondary dormancy, termed skotodormancy. The seeds first lose their ability to be promoted to germinate by gibberellic acid, and then lose their ability to be promoted by red light. A combination of red light and gibberellic acid will break skotodormancy for longer than either alone, but red light and benzyladenine together are much more effective. Desiccation of skotodormant seeds does not diminish their dormancy. Embryos dissected from skotodormant seeds will germinate, and are as capable of radicle expansion in the osmoticum polyethylene glycol as are newly‐imbibed seeds. Hence skotodormancy is a whole seed dormancy and does not reside within the embryo as an inherent block to germination processes, but as an inability to respond to the stimulation of red light or to ho

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb02663.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThe effect of morphactin (methyl‐2‐chloro‐9‐hydroxyfluorene‐9‐carboxylate) on the content of several plant growth substances in bean roots was determined. Beans (Phaseolus vulgarisL. cv. Spartan) were soaked in aqueous solutions of morphactin, 1 x 10‐4, 1 x 10‐5, and 1 x 10‐6Mand grown in moist vermiculite. As controls were used beans grown in water‐moistened vermiculite either intact or having the root tips removed (decapped). The roots, morphactin‐treated, controls, and the decapped ones were analyzed for indol‐3‐yl acetic acid (IAA), indol‐3‐yl acrylic acid (IAcA), indol‐3‐yl pyruvic acid (IPyA), indol‐3‐yl lactic acid (1LA), abscisic acid (ABA), gibberellins GA1, GA3, GA4, and GA9using gas‐liquid chromatographic methods. Morphactin, while affecting the geotropical responses, changed also the growth substance content of roots. IAA, ABA, GA1, and GA9contents decreased, IPyA, IAeA, GA3, and GA4contents were not affected and ILA content increased slightly with increasing dosages of morphactin. Growth substance pattern of decapped roots resembled that of the roots treated with the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb02664.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractCultures ofEuglena gracilis(strain Z from French CNRS collection) can be made cadmium resistant if grown in a medium with 5x10‐4Mcadmium chloride. This resistance is reflected by the appearance of a second exponential growth phase. The development of this resistance was studied at the cellular level by determining the relative content of DNA at different stages of the cell cycle in an asynchronously grown culture. The culture was followed until the second, cadmium resistant, growth phase had reached its stationary state.During the first exponential growth phase, cells were mostly in the late period of DNA synthesis (stage S of the cell cycle), or in the gap preceding mitosis (stage G2of the cell cycle). In addition, some cells contained high multiples of the normal amount of DNA. In the beginning of the second exponential growth phase, a few cells were again in G1(the post mitotic stage of the cell cycle preceding DNA synthesis). These G1cells were predominant at the end of the second growth period. During the second stationary phase the DNA content of the cadmium treated cells was similar to the stationary phase of the control culture. Cells had stopped growing in G1with an unreplicated genome. The implications of these data are discusse

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb02665.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThe influx of Rb+into the roots of two barley varieties (Hordeum vulgareL. cv. Salve and cv. Ingrid) from a K+‐free86Rb‐labelled nutrient solution with 2.0 mMRb+, was checked at intervals from day 6 to day 18. The control plants were continuously grown in complete nutrient solution containing 5.0 mMK+, while two other groups of plants were grown in K+‐free nutrient solution starting on day 6 and between day 6 and day 9, respectively. The pattern of Rb+influx was similar for both varieties, although their efficiencies in absorbing Rb+were different. The relationship between Rb+influx and K+concentration of the root could be interpreted in terms of negative feedback through allosteric control of uptake across the plasmalemma of the root cells. Hill plots were bimodal, but in the opposite direction. The Hill coefficients, reflecting the minimum number of interacting allosteric binding sites for K+(Rb+), were low (≤–3.0). It is discussed whether the threshold value, that is the breaking point in the Hill plot, is indicative of a changed efficiency of transporting units for K+(Rb+) transport to the xylem. Moreover, feedback regulation might be involved in transport of K+between root and shoot. The variation in K+concentrations in the roots and shoots of control plants were cyclic but in phase opposition despite an exponential growth. The average K+concentration varied only slightly

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb02666.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractIn recent years liquid medium has been shown to be better than agar‐gelled medium for production of haploids by anther culture. However, on addition of charcoal to agar medium the anther response inDatura innoxiaMill, increases dramatically and is better than in liquid medium. For anthers with pollen at the premitotic stage, the best result was observed with 1% charcoal in Difco agar and 1.5% in Normal agar. The effect is possibly due to adsorption of substances inhibitory to androgenesis and emanating from anthers, as well as to substances present in the nutrient medium and aga

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb02667.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractPhenylalanine ammonia‐lyase (PAL) activity increased 8‐ to 12‐fold in pine (Pinus elliotiiEngelm.) callus tissue within 2 days after subculturing on fresh medium. Factors such as increasing the sucrose content of the media, imposing additional tissue in jury or subculturing more frequently did not cause additional stimulation of PAL activity. The rapid increase in PAL activity appeared to be due to enzyme activation, since cycloheximide did not appreciably reduce the stimulation of PAL activity. The subsequent loss of increased PAL activity with age was reduced by cycloheximide and a cool growth enviro

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb02668.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThe decapitated primary root of 3‐day‐old Alaska pea seedlings has been used as a test system to determine the activities on lateral root formation of six auxins, six cytokinins and several other naturally‐occurring compounds. Their effects were assessed on (1) the initiation of lateral root primordia, (2) the emergence of visible lateral roots, and (3) the elongation of these laterals.All the auxins, at the optimum concentration of 10‐4M, promoted the initiation of lateral root primordia, and all except 3‐indolylpropionic acid inhibited the elongation of the resulting lateral roots. Their effects on the emergence of laterals were small and varied. All the cytokinins, at 10‐6Mand above, inhibited both the initiation and the emergence of lateral roots, zeatin being the most powerful inhibitor. The emergence process was about twice as sensitive as the initiation of primordia to the presence of cytokinins. The cytokinin ribosides were generally less active than the free bases. Abscisic acid and xanthoxin inhibited both emergence and elongation, the concentration for 50% decrease of emergence being about 10‐4M. Gibberellic acid had little clear effect on any of the three criteria. Nicotinic acid and thiamine at 10‐3Mpromoted both the initiation of primordia and their emergence: pyridoxal phosphate stimulated both emergence and elongation but did not influence the initiation of primordia. Adenine and guanine had little effect but decreased root elongation some 25%.The strong inhibiting effect of the cytokinins may well be the basis for the marked inhibition exerted by the root‐tip on lateral root formation, while the promoting effects of auxins may explain the previously observed promotion of lateral root formation by the young sho

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb02669.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY