An Analysis of the Effect of Alternating Temperatures on Germination of Lycopus europaeus L.

The germination of Lycopus europaeus seeds depends absolutelyon exposure to light and fluctuating temperatures. Studies oftemperature responses were made to establish the minimum fluctuationrequired for a response, the interaction of temperature andexposure time in different parts of the alternating temperaturecycle, and the effects of successive transfers between cyclingtemperature conditions. There was a complex interaction betweenthese three. The minimum fluctuation never fell below 6.5 °Cbut varied up to c. 15 °C according to other test conditions.High temperatures favoured rapid responses, and exposure totemperatures above 20 °C in one or other phase of the temperaturecycle was essential for a full response. No response occurredeither at any temperature under constant conditions, or if onlyone temperature change was given. Under some conditions a singlecycle of alternating temperatures, including two changes oftemperature, promoted high germination rates.     

Temperature and Seed Storage Longevity

Seed survival data for eight diverse species, namely the cerealbarley (Hordeum vulgare L.), the grain legumes chickpea (Cicerarietinum L.), cowpea [Vigna unguiculata (L.) Walp.] and soyabean [Glycine max (L.) Merr.], the timber trees elm (Ulmus carpinifoliaGleditsch.), mahogany (Swietenia humilis Zucc.), and terb (Terminaliabrassii Exell.), and the leaf vegetable lettuce (Lactuca sativaL.) were compared over a wide range of storage environments(temperatures from –13 °C to 90 °C, seed moisturecontents from 1.8 to 25% f. wt) using a viability equation developedpreviously. In accordance with that equation, the effect oftemperature on seed longevity was dependent upon the temperaturerange. The temperature coefficients of the viability equationdid not differ significantly (P > 0.05) among the eight speciesdespite their contrasting taxonomy. Thus the quantitative relationbetween seed longevity and temperature does not vary among diversespecies. The same conclusion was obtained for the coefficientsof a proposed alternative model of the relation between seedlongevity and temperature. The implications of the two temperaturemodels in the viability equation for extrapolations to low andvery low temperatures are discussed. Seed storage, seed longevity, seed moisture, temperature, viability equation, genetic resources conservation, Cicer arietinum L., Glycine max (L.) Merr., Hordeum vulgare L., Lactuca sativa L., Swietenia humilis Zucc., Terminalia brassii Exell., Ulmus carpinifolia Gleditsch., Vigna unguiculata (L.) Walp     

Effects of Decapitation and Benzyladenine on Growth and Yield of Cowpea [Vigna unguiculata (L.) Walp.]

A study was undertaken to define more clearly the role of theearly loss of apical dominance on yield of cowpea [Vigna unguiculata(L.) Walp. cv. Vita-5]. Decapitation at the fifth leaf stageresulted in an increase in branching components, yields andharvest indices, while vegetative d. wt accumulation was reduced.Foliar-applied sprays of 6-benzyladenine had no effect on branchingunless combined with decapitation and no significant effectson yield over that of controls were observed. However, harvestindices were increased by 50 per cent. Vigna unguiculata (L.) Walp., cowpea, apical dominance, decapitation, 6-benzyladenine     

Germination Strategy of a Woodland Grass: Milium effusum L.

Caryopses of Millum effusum L. were collected from wild plantsin south-east England Laboratory tests established that germination immediately followingharvest occurred relatively slowly at a narrow range of temperatures;optima occurred at 16 °C in the first weeks of experimentsand subsequently at 21 °C, at which the highest proportionof germination occurred Levels of germination increased aftercaryopses had been stored at 25 °C over anhydrous calciumchloride, when tests were done at fluctuating temperatures;or after chilling treatments at 2 °C, or high temperature(26 and 31 °C) conditioning treatments of imbibed seed Freshlyharvested caryopses displayed an inverse relationship betweentemperature and time taken to germinate resulting from variationsin the speed at which after-ripening processes were completedat different temperatures These responses were used to construct a model representativeof all populations of M effusum throughout its natural range.The results suggested that a coherent and plausible interpretationof the responses could be arrived at by suggesting that adaptationto local conditions depends largely on phenotypic plasticityarising from interactions between the germination characterand a variety of differing climatic conditions Millum effusum L wood millet, germination, temperature response     

The Influence of Temperature on Seed Germination Rate in Grain Legumes: I. A COMPARISON OF CHICKPEA, LENTIL, SOYABEAN AND COWPEA AT CONSTANT TEMPERATURES

For a single seed population of each of four species of grainlegume positive linear relationships were shown between temperatureand rate of germination for different fractions (G) of eachpopulation, from a base temperature, T_b(G), at which germinationrate is zero, to an optimum temperature, T_o(G) at which germinationrate is maximal. At constant temperatures warmer than T_o(G)there were negative relations (probably linear) between temperatureand rate of germination to the maximum temperature for germination,T_m(G), Within each population T_b(G) did not differ, but it didvary between species, viz.0.0?C, 0.25?C, 4.and 8.5?C for chickpea(Cicer arietinum L.), lentil (Lens culinaris Medic.), soyabean(Glycine max [ Merr.) and cowpea (Vigna unguiculata [L.] Walp.),respectively. In contrast, T_o(G) varied both within each populationand also between the four species: 80% of seeds in each populationhad T_o(G) values within the range 31.8?C to 33.8 ?C, 24.0?Cto 24.4?C, 34.0?C to 34.5?C and 33.2?C to >40?C, respectively.Values of T_m(G) were much more vanable: the 80% population rangewas 48 .0?C to 60.8?C for chickpea, 31.8?C to 34.4?C for lentiland 46.8?C to 55.2?C for soyabean; reliable estimates couldnot be made for cowpea, but the results suggest higher and morevariable values of T_m(G) than in the other three species. Atsub-optimal temperatures the distribution of thermal time forthe different fractions of each population was normal, exceptfor lentil where it was log-normal. A single equation is proposedto describe the influence of sub-optimal temperatures on ratesof germination for whole seed populations. At supra-optimaltemperatures, variation in thermal time for the different fractionsof each population was only slight. The implications of thesefindings for the adaptation of grain legume crops to differentenvironments, and for the screening of germplasm, are discussed. Key words: Seed germination rate, temperature, grain legumes     

Effects of Temperature and Water Potential on Germination, Radicle Elongation and Emergence of Mungbean

Controlled environment experiments were performed to determinethe effects of temperature and water potential on germination,radicle elongation and emergence of mungbean (Vigna radiata(L.) Wilczek cv. IPB-M79-17-79). The effects of a range of constant temperatures (15–45°C) and water potentials (0 to –2.2 MPa) on germinationand radicle elongation rates were studied using an osmoticumtechnique, in which seeds were held against a semi-permeablemembrane sac containing a polyethylene glycol solution. Linearrelationships were established between median germination time(Gt₅₀) and water potential at different temperatures, and betweenreciprocal Gt₅₀ (germination rate) and temperature at differentwater potentials. Germination occurred at potentials as lowas –2.2 MPa at favourable temperatures (30–40 °C),but was fastest at 40 °C when water was not limiting, withan estimated base temperature (T_b) of about 10 °C. Subsequentradicle elongation, however, was restricted to a slightly narrowertemperature range and was fastest at 35 °C. The conceptof thermal time was used to develop an equation to model thecombined effects of water potential and temperature on germination.Predictions made using this model were compared with the actualgermination obtained in a related series of experiments in columnsof soil. Some differences observed suggested the additionalimportance of the seed/soil/water contact zone in influencingseed germination in soil. Seedling emergence appeared to reflectfurther the radicle elongation results by occurring within anarrower range of temperatures and water potentials than germination.Emergence had an estimated T_b of 12.6 °C and was fastestat 35 °C. A soil matric potential of not less than about–0.5 MPa at sowing was required to obtain 50% or moreseedling emergence. Key words: Germination, temperature, water potential     

Effect of Temperatures on Dormancy and Germination in Three Species in the Lamiaceae Occurring in Northern Wetlands

In the temperate region temperature is the main factor influencing the germination period of plant species. The purpose of this study was to examine effects of constant and fluctuating temperatures on dormancy and germination under laboratory and field conditions in the three wetland species Lycopus europaeus, Mentha aquatica and Stachys palustris. The results should give indications if the temperature-dependent regulation of dormancy and germination is phylogenetically constrained. Tests for germination requirements showed a minimum temperature for germination of 9 °C in Mentha and 12 °C in Lycopus and Stachys, and a maximum temperature of 33 °C for Lycopus and 36 °C for Mentha and Stachys. Fluctuating temperatures promoted germination in all three species but the amplitude required for high germination (>50%) differed: it was 8 °C in Mentha, 10 °C in Stachys and 14 °C in Lycopus (mean temperature 22 °C). The effect of temperatures on the level of dormancy was examined in the laboratory by imbibing seeds at temperatures between 3 °C and 18 °C for periods between 2 and 28 weeks, as well as by a 30-month burial period, followed by germination tests at various temperatures, in light and darkness. In the laboratory only low temperatures (≤12 °C) relieved primary dormancy in seeds of Lycopus, while in Mentha and Stachys also higher temperatures lead to an increase of germination. Dormancy was only induced in Lycopus seeds after prolonged imbibition at 12 °C in the laboratory. Buried seeds of all species exhibited annual dormancy cycles with lower germination in summer and higher germination from autumn to spring. Exhumed seeds, however, showed considerable differences in periods of germination success. Dormancy was relieved when ambient temperatures were below 12 °C. Ambient temperatures that caused an induction of dormancy varied depending on species and test condition, but even low temperatures (8 °C) were effective. At high test temperatures (25 °C) in light, exhumed seeds of all three species showed high germination throughout the year. The three species showed various differences in the effects of temperatures on dormancy and germination. Similarities in dormancy and germination found among the species are in common with other spring-germinating species occurring in wetlands, so it seems that the temperature dependent regulation of dormancy and germination are related to habitat and not to phylogenetic relatedness.     

The Influence of Genotype, Temperature and Moisture on Seed Longevity in Chickpea, Cowpea and Soya bean

Seed of three chickpea (Cicer arietinum L.), three cowpea [Vignaunguiculata (L.) Walp.] and four soya bean [Glycine max (L.)Merr.] cultivars were hermetically stored for up to 2 yearsin various constant environments which included temperaturesfrom —20 to 70 °C and moisture contents (fresh weightbasis) from 5 to 25 per cent. In all cases the survival curvescould be described by negative cumulative normal distributions.The longevity of the various seed lots differed but the valueof the standard deviation (the reciprocal of which gives theslope of the survival curve when percentage germination is transformedto probit) was the same for all cultivars within a species whenstored under similar conditions. Within each species the relativeeffects of moisture and temperature on longevity did not differsignificantly between cultivars. In all three species therewas a negative logarithmic relationship between seed moisturecontent and longevity, but the relative effect of moisture contentdiffered between the species: differences in the longevity ofsoya bean seed as a function of moisture content were less thanfor either cowpea or chickpea. The relative effect of temperatureon seed longevity did not differ between the three species,and the seed of all three species showed increasing temperaturecoefficients for the change in rate of loss of viability withincrease in temperature. The complete pattern of loss in viabilityin all three species can be described by a single equation whichwas developed for barley and has also been shown to apply toonion seed. The constants applicable to the three grain legumeshave been calculated so that it is now possible to predict percentageviability of any seed lot of these species after any storageperiod under a very wide range of storage conditions. Cicer arietinum L., chickpea, Glycine max (L.) Merr., soya bean, Vigna unguiculata (L.) Walp., cowpea, seed longevity, seed storage, moisture content, temperature     

Sensitivity to Low Temperature in Pollen Germination and Fruit-Set in Cicer arietinum L.

Cicer arietinum L. cv. G 62404 was seen to have a very low fruit-setpercentage at low temperatures and as temperatures increased,either in nature or in culture conditions, the fruit-set alsoincreased. This effect of temperature could also be seen inpercent pollen germination and pollen tube growth. M 450, amutant of G 62404, was seen to have a better fruit-set percentageat low temperature and better pollen germination. This may bedue to differences in malic acid concentration, which increasedpollen germination, and pollen tube growth under in vitro cultureconditions.     

Germination Responses of Pinus densiflora Seeds to Temperature, Light and Interrupted Imbibition

Germination responses of Pinus densiflora Sieb. et Zucc. seedsto temperature and light were examined with a special interestin the gap-detecting mechanisms in germination, i.e., responsesto fluctuating temperature and sensitivity to leaf-canopy transmittedlight. Simple linear relationships were observed between thetemperature in the suboptimal range and the germination rates,i.e., the reciprocals of the time taken to germinate by theseed subpopulations with 10–90% germination. The ‘thermaltime’ concept could thus be used effectively to analysethe responses to varying temperatures and light. Neither shiftsnor alternations of ambient temperature affected the thermaltime required for germination; the profile of the change inpercentage germination plotted against thermal time for theseed population was almost identical among various constantand varying temperature regimes. Seed germination was completelyinhibited by simulated leaf-canopy light, thus indicating thatP. densiflora seeds have a gap-detecting mechanism in the formof canopy-light sensitivity. Moreover, 1–7 d interruptionof imbibition with dehydration had little effect on the finalpercentage and thermal time required for germination, suggestingthat the germinating seeds of this species have a great capacityto withstand the fluctuating moisture conditions of the exposedsurface of soil. Key words: Germination rate, temperature, light, moisture, gap-detecting mechanism, Pinus densiflora     

Changes in Lipids of Bean Seeds (Phaseolus vulgaris) and Corn Caryopses (Zea mays) Aged in Contrasting Environments

Seeds of French bean (Phaseolus vulgaris L. cv. The Prince)and caryopses of sweet corn (maize; Zea mays L.F1 hybrid Firstof All) were stored in environments of 79% relative humidityand 25 °C, 80% r.h. and 40 °C or 100% r.h. and 45 °C,giving ageing (loss of gcrminability and vigour) over periodsof months, weeks or days, respectively. The relationship betweenchanges in lipids and changes in germinability or vigour wasunaffected in general by the speed of ageing. In the corn caryopsesthere was no evidence of hydrolysis of phospholipids or peroxidationof fatty acids during ageing. In the bean seeds phosphatidicacid increased during the ageing period and phosphatyl cholinedeclined. The percentage of fatty acids as hnolenic acid initiallyfell during bean ageing, but in the slower ageing conditionsit rose again as germination reached zero. In bean, the presenceof phosphatidic acid could be a sensitive indictator of lossof vigour, but relative proportions of the different fatty acidswould be a misleading indicator of quality. Rapid artificialageing may be an adequate model, in some species, of ageingat moderate speeds and of ageing under some ambient conditions. French bean (Phaseolus vulgaris L. cv. The Prince), sweet corn (maize, Zea mays L., Fl hybrid First of All), seed ageing, phospholipids, fatty acids     

Germination of Lycopus europaeus L. in response to fluctuating temperatures and light

Germination of Lycopus europaeus depends absolutely on botha diurnal temperature fluctuation and light. Studies of theparameters and interactions of these two environmental factorsproduced no evidence of critical temperatures for germination,which could occur over a wide range of different temperaturecombinations provided the magnitude of the diurnal fluctuationexceeded 7 °C. Successive temperature cycles produced acumulative effect, and both a temperature rise and a fall wereessential for the completion of processes leading to germination.The time interval between these two temperature changes wascriticial, showing both a minimum and a maximum which variedwith temperature conditions. Light irradiation was essentialat some point in the cycles, though it was not tied to any particularphase; brief light breaks at repeated intervals were as effectiveas much longer periods of continuous illumination     

Characterization of the Germination Responses to Temperature of Lettuce (Lactuca sativa L.) Achenes

Germination tests were done on 23 cultivars of lettuce (Lactucasativa L.) comprising a variety of different morphological formsselected for cultivation at various seasons. Significant differences at the upper limit of temperature tolerancewere found between different cultivars: maximum temperaturesfor 50 per cent germination ranged from 23 to 32 °C, andsusceptibility to the induction of secondary dormancy by hightemperatures varied widely from one cultivar to another. Nocorrelations were established between germination responsesand heading type, achene colour or growing season The germination responses of all cultivars at temperatures fromjust above 0 to 20 °C were closely similar and results froma large number of experiments were used to produce a standardgermination reference curve foti culvars of L. sativa. Departfuresrom this curve were found to arise predominantly from variationsin seed quality or test conditions rather than from the genotypeof the cultivar. Detailed comparisons of germination at all possible combinationsof alternate and constant day/night temperatures are presentedfor two cultivars. One with relatively high tolerance to high-temperatureinducedinhibition, the other with low tolerance. The results are discussed in relation to the original distributionof the species as a wild plant and its history of cultivationby man. Lactuca sativa L., Lettuce, achene germination, temperature response     

Interrelationship between Meristematic Regions of Developing Inflorescences of Four Cereal Species

A cultivar from each of four cereal species (Avena sativa L.,cv. Swan, Hordeum vulgare, L., cv. Clipper, Triticum aestivumL., cv. Gabo, and Secale cereale L., cv. South Australian Rye)was grown in controlled environment chambers in a 10-h photoperiod(short days) or 10-h photoperiod supplemented with a 6-h extensionby incandescent light. The developmental morphology of the inflorescenceswas followed to ascertain whether there were any common developmentalinterrelationships between the species. Inflorescence internodeelongation was initiated when the floret initial first appeared,irrespective of whether it occurred on the most advanced lateralspikelet or on the terminal spikelet of the rachis. The glumes(infertile bracts) of the terminal spikelet of the rachis wereinitiated when the first second-order inflorescence branch appeared,irrespective of whether the second-order inflorescence branchwas a floret initial or a lateral spikelet, as in Triticum sp.,or an inflorescence (panicle) branch, as in Avena sp. Cessationof the activity of the apical meristem, as measured by primordiumformation, was not correlated with any particular stage of floraldevelopment but appeared to be due to a lack of nutrients causedby an increasing competitiveness for the available nutrientsfrom the developing spikelets which are situated closer to thevascular system than the apical meristem.     

The Interaction of Heat and Smoke in the Release of Seed Dormancy in Seven Species from Southwestern Western Australia

Exposure to high temperatures (40–60 °C) over severaldays to months (simulating summer soil conditions) or to extremelyhigh temperatures (80–120 °C) for periods rangingfrom minutes to several days (simulating the heat of an extremefire) promoted germination in five (including one legume species)of the seven species tested from southwestern Australia. Heat,a collective term for high temperature (HT) and extremely hightemperature (EHT), has previously been used to promote germinationin species with impermeable seed coats (many of which are legumes).If heat is found to promote germination in species with permeableseed coats, it could be of use in the release of dormancy forcommercial development of native plants. Here we report thatelevated storage temperatures (50 °C for 45 and 90 d or60 °C for 45 d) and EHT (100 °C for 3 h and 120 °Cfor 30 min) alone, and in addition to smoke, directly promotegermination of the refractory species Actinotus leucocephalus,Anigozanthos manglesii, Gompholobium knightianum, Loxocaryastriatus and Stylidium affine. Germination of Sowerbaea laxifloraseed was not improved with heat alone but was improved by thecombination of heat and smoke. Seed of Schoenus unispiculatusdid not germinate in response to any of the treatments. Interactionsbetween the effect of temperature, the duration of heat exposureor smoke were detected in all species. Whilst most species demonstratedan interaction between heat and time, not all species were affectedby smoke alone. This was illustrated by an interaction betweensmoke and HT found only in Actinotus leucocephalus, Anigozanthosmanglesii and Stylidium affine or smoke and EHT in A. manglesiiandS. affine . Smoke and exposure time to heat influenced thegermination of Actinotus leucocephalus,Anigozanthos manglesiiand L. striatus in response to HT and only S. affine appearedto demonstrate an interaction between smoke and EHT. The variationsfound in the interactions between treatments suggest that germinationevents occur over a range of conditions both spatially and temporallywhich may facilitate seedling survival and limit competitionbetween emergents. Copyright 2001 Annals of Botany Company Smoke, heat, fire, seedbank, seed dormancy, seed germination, Western Australia     

Temperature and the Vegetative Growth of Three Saudi Arabian Herbs

In Saudi Arabia, Artemisia abyssinica is a perennial, sand-stabilizingspecies which is common in the great inland deserts; Rumex nervosusis a medicinal herb of lowland distribution; Verbesina encelioidesis an arable weed of similar distribution to R. nervosus, butis also locally common in certain fertile inland and montanehabitats. Typical environments of these species are sharplycontrasted in climate. To see if temperature played any partin limiting these species to their respactive habitats, seedlingsof all three (including two potentiallyseparate lowland andmontane populations of V. encelioides) were grown under controlled-environmentconditions over a range of different temperatures. Artemisia abyssinica proved to be innately slow-growing andto exhibit a high temperature optimum, though with a shallowresponse-gradient in respect of growth over-all and of partitioningbetween root and shoot. Rumex nervosus and both populationsof V. encelioides were quite unlike this, being faster-growing,plastic, and with clear, low temperature-optima Despite certain morphological distinctions, the two populationsof V. encelioides differed little in their whole-plant physiology.However, previous work had established that the montane population,like A. abyssinica, was protected from germination at high constantor fluctuating temperatures. The lowland population, like R.nervosus, was not. Differential conbinations of germinativeand vegetative behaviour were thus postulated as facilitatingthe wide natural distribution of V. encelioides. General conclusions were also drawn concerning the locationon a mesic-xeric continuum of the three species, and also oftwo others studied in a set of experiments published previously. Artemisia abyssinica Sch. Bip., Rumex nervosus Vahl., Verbesina encelioides (Cav.) Benth. et Hook., F. ex A. Gray, growth analysis, temperature, rsponse surfaces, plant distribution     

Spore Germination and Gametophyte Development in Three Species of Asplenium

Laboratory and field experiments involving Asplenium ruta-murariaL., Asplenium trichomanes L. subsp. quadrivalens D.E. Meyeremend. Lovis and Asplenium scolopendrium L. [= Phyllitis scolopendrium(L.) Newm.] revealed differences in their temperature requirementsfor germination and in their sexual development on soil. Thegermination responses of A. trichomanes and A. scolopendriumto culture temperatures of 10, 15, 20 and 25 °C were verysimilar and all spores were able to germinate at 10 °C.Spores of A. ruta-muraria differed in that germination was slowerat 15-25 °C and very much delayed, or even inhibited, at10 °C. Both laboratory and field cultures of A. trichomanesand A. scolopendrium produced male, female and bisexual gametophyteswhereas those of A. ruta-muraria produced only males and bisexuals.The ecological significance of these differences is discussed.Copyright1994, 1999 Academic Press Fern, Asplenium ruta-muraria, Asplenium trichomanes, Asplenium scolopendrium, Phyllitis scolopendrium, spore germination, gametophyte, reproductive biology, temperature effects, field experiments     

Thermodormancy Release of Celery Seed by Gibberellins, 6-Benzylaminopurine, and Ethephon Applied in Organic Solvent to Dry Seeds

The emergence of celery (Apium graveolens L. cv. Utah 52–70)seeds was promoted by growth regulators when exposed to hightemperatures during the germination period. The growth regulatorswere applied to dry seeds prior to sowing, by means of the organicsolvent dichloromethane (DCM). A mixture of gibberellins A₄and A₇ (GA_4/7) strongly enhanced emergence at a high day-timetemperature of 35°C alternating with night temperaturesof 20°C and 25°C; however, emergence was very poor whenthe night temperature was raised to 30°C. Under the latterregime, only mixtures of GA_4/7 with 6-benzylaminopurine (BA)or with 2-chlorophosphonic acid (ethephon) promoted seed emergence.However, BA and ethephon applied separately or in combinationwere much less effective in enhancing seed emergence withoutthe addition of GA_4/7, under all the temperature regimes.     

A Model for Germination Responses to Alternating Temperatures

When seeds of Chenopodium album are imbibed in 0–01 Mpotassium nitrate solution in the light at constant temperature,percentage germination increases to an optimum at 24 °C,above which it decreases. These relationships are linear ifpercentage germination values are transformed to normal deviates.At supra-optimal temperatures, alternating temperatures havelittle or no effect on this basic relationship. However, atsub-optimal temperatures normal deviate germination increaseslinearly with amplitude at constant mean temperature and theincreases are relatively greater at lower mean temperatures.The effect of amplitude is also greater when more time is spentat the wanner temperature in the diurnal cycle. Seeds of Panicummaximum show very similar responses except that the effect ofamplitude is greater when a shorter time is spent at the warmertemperature in the diurnal cycle. These observations form thebasis of a quantitative model which, at sub- and supra-optimaltemperatures, respectively, accounts for 90 and 75% of the variationin germination of C. album seeds subject to a very wide rangeof thermal environments on a two-dimensional temperature gradientplate. The data presented for P. maximum are less comprehensive,but again the model accounts for 80% of the variation. The relevanceof the same model to two unrelated species from different climatesand of different ecological behaviour suggests that it may begenerally useful in determining optimum temperatures for seedviability testing regimes and ultimately for predicting fieldbehaviour These results allow the producers to improve the productionof homogeneous populations of cyclamen seedlings Chenopodium album L., Panicum maximum Jacq., seed dormancy, germination, alternating temperatures, temperature gradient plate     

Tuberization in Potato at High Temperatures: Gibberellin Content and Transport from Buds

Warm temperatures (35°C day/30°C night) which inhibittuberization in potato (Solanum tuberosum L., cv. Sebago) increasedgibberellin activity in crude extracts from buds, but not frommature leaves, as determined by the lettuce hypocotyl bioassay.Changes in the growth of tubers and stolons indicate the occurrenceof basipetal movement of GA₃ applied to the terminal bud ora mature leaf. ¹⁴C labelling from GA₃ or mevalonic acid injectedjust below the terminal bud was recovered in the lower shoot,stolons and tubers, but the amount transported was greater atcool temperatures (20/15°C). It is concluded that high temperaturespromote the synthesis of gibberellin in the buds rather thantransport to the stolons. Solanum tuberosum L., potato, tuberization, gibberellin