摘要:

RosaPaul's Scarlet’cell suspension cultures were used as a test system for working out a method of viability and drug‐sensitivity determination based on plating efficiency. High plating efficiencies (80–95%) were obtained on a simple synthetic medium when aggregates of a mean size ofc. 100 cells/unit from exponential phase cultures were plated at a density of 1500 units/plate in the middle layer (5 ml) of three layers of the agar‐solidified medium (total = 30 ml). This 3‐layer plating technique produces homogeneous colony growth and simplifies the microscopical evaluation of plating efficiencies. The reduction of plating efficiencies seen when the smaller aggregates of stationary phase cultures were plated was mainly due to low cell density and could be overcome by enriching the medium with various supplements. Reconstitution experiments using mixtures of inactivated and non‐inactivated aggregates demonstrated that plating efficiency can be taken as a goodmeasure of viability. The described plating technique was found to be more sensitive and reliable compared to two other methods for determiningp‐fluorophenylalanine‐sensitiv

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00889.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

A simple tissue culture protocol was used to examine phloem differentiation. Sieve tube elements differentiated fromColeus blumeiBenth. pith parenchyma when pith blocks were explanted on to an agar medium containing sucrose and indole acetic acid. Growth regulator concentration had surprisingly little influence on the production of phloem cells. Increasing the availability of sucrose, however, resulted in an enhancement of phloem differentiation. Evidently phloem and xylem differentiation began at the same time in this system, and the concentration of sucrose determined the relative production of phloem cells.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00890.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Deterioration of soybean [Glycine max(L.) Merr. cv. Essex] seeds during accelerated aging at 41°C and 100% relative humidity predisposes the embryonic axis to injury during the initial period of imbibition. This injury was prevented or greatly reduced in severity when excised axes were imbibed on blotters containing 30% polyethylene glycol which slowed the rate of water uptake and when axes were pre‐equilibrated to a high moisture level. Rates of water uptake by “high”(no treatment) and “low vigor”(accelerated aged) excised axes were identical. However, high vigor axes tolerated rapid water uptake during early imbition, whereas low vigor axes did not. Leakage of electrolytes during early imbibition was nearly six times greater in low than in high vigor axes. Polyethylene glycol significantly reduced the leakage of electrolytes from both low and high vigor axes. The data are in agreement with the hypothesis that seed deterioration in soybeans involves membrane changes which may predispose embryonic tissues to injury during imbibition. Reduction of the rate of water uptake during the initial period of imbibition would allow extra time for membrane repair or rearrangement, thus permitting the tissues to develop in a more orderly manner. The data indicate that deterioration in soybean seeds involves, at least in part, a decrease in ability of seed axes to tolerate rapid water uptake at the start of imbibition and that this weakness may be compensated by osmotic control of wa

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00891.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The effects of foliar application of potassium 3,4‐dichloroisothiazole‐5‐carboxylate (TD‐1123) and S,S,S‐tributyl phosphorotrithioate (DEF) on some physiological events that occur in cotton (Gossypium hirsutumL.) leaves are reported. Transport of14C from cotton leaves was significantly reduced as soon as 1 day after treatment with DEF. In addition the DEF‐treated leaves exhibited reductions in water potential recovery values (predawn measurements), stomatal conductance, specific weights, soluble N content, and an alteration in free amino acid distribution. Little change in any of these parameters was noted in leaves treated with TD‐1123 alone. A sequential treatment of TD‐1123 followed in 10 days with DEF had an apparent synergistic effect in that the effect on most parameters measured was more pronounced and occurred earlier in such leaves than in those treated with either

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00892.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Nitrogen deficiency in cotton plants (Gossypium hirsutumL.) increased the threshold water potentials for both stomatal closure and leaf senescence (defined as loss of chlorophyll and protein) during drought. These studies attempted to answer two questions: (1) What is the basis for the N/water interaction on senescence? (2) Is there a direct relationship between stomatal closure and senescence?Young and old leaves from N‐deficient and N‐sufficient plants maintained their relative sensitivities to water stress when excised leaf discs were floated on solutions of polyethylene glycol in dim light. In this leaf disc system, both leaf aging and N deficiency increased the threshold water potential for senescence. Leaf aging and N deficiency also decreased the concentration of exogenous abscisic acid necessary to initiate senescence in discs. A role for cytokinins in controlling senescence could not be clearly shown.In young leaves of both N‐deficient and N‐sufficient plants, stomata closed at water potentials much higher than those causing senescence. During leaf aging, the water potentials causing senescence increased more than those causing stomatal closure. The two processes thus occurred at about the same potentials in the oldest leaves. These data argue against a general cause‐and‐effect relationship between stomatal closure and senescence. Rather, each process apparently responded independently to absicsic acid accumulated dur

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00893.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

During the growth of maize (Zea maysL.cv. INRA F7× F2) under constant climatic conditions, the effects of reductions in irradiance simulating a cloudy day were studied. Hourly and daily measurements made in an assimilation chamber (C23A) showed important and lasting effects in root activity. After reduction of photosynthesis, it took approximately 2 hours to start a lowering of the uptake of NO3−and NH4+, three hours for K+and four hours for phosphate. Root respiration started to fall after 3 hours. The level to which these activities were reduced also varied. Phosphate uptake was reduced by a mean of 27%, nitrate uptake by 47%, and K+uptake by 55% while the root respiration was reduced by 55%. After return to the initial irradiance, root activities took 3 days to recover their initial rates. Shoot respiration was re‐established after one day, while the effects on photosynthesis and transpiration were immediate. The delay of the effect of a change of photosynthesis on the activities of the root, indicates the existence of considerable metabolic reserves. Over longer periods, root metabolism depends on photosynthetic assimilates, but in the short term it is much more dependent on the level of metabolic reserves than on the direct flow of photosynthetic transloc

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00894.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00895.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY