Floral Induction of Xanthium strumarium in Long Days

An efficient method of inducing flowering in the normally strictshort-day plant, Xanthium strumarium L., in long days is described.Plants were grown in 16-h long days and subjected to two thermocycleswith a root application of gibberellic acid at the 8th h ofthe light period. A thermocycle was defined as follows. Forthe first 8 h of the 24-h cycle, the temperature was 4 °C;for the remaining 16 h, it was 23 °C. The light was on forthe first 16 h and off for the remaining 8 h. Xanthium strumarium L., floral induction, thermoperiod, gibberellic acid     

Interaction Between Mineral Nutrients, Cytokinin and Gibberellic Acid During Growth of Sorghum at High NaCI Salinity

Sorghum bicolor (L.) Moench, cv. 610, adapted to high salinitywas able to grow at 300 mol m^–3 NaCl only when half-strengthHoagland's solution was enriched with mineral nutrients. Theoptimal growth rate was observed in full strength Hoagland'ssolution; at higher or lower concentrations growth rates werelower. In contrast, growth rate of plants exposed to 150 molm^–3 NaCl was not affected by similar modification of theHoagland solution concentration. At high salinity, additionof cytokinin (CK) or gibberellic acid (GA), or a mixture ofboth, can induce the same effect on growth as the increasedmineral nutrient concentration. Phytohormones and increasedmineral concentration have similar effects, possibly becausean imbalance in phytohormones, rather than a mineral deficiency,limits growth at 300 mol m^–3 NaCl in the presence of half-strengthHoagland solution. The change in mineral concentration in thenutrient medium, in addition to its nutritional effect, alsoapparently acts as a signal involved in hormonal balance whichallows growth at high salinity. Exposure of Sorghum to 300 molm^–3 NaCl causes a decrease in the range of nutrient concentrationswhich can sustain growth. Adjustment of the nutrient concentrationmay induce the synthesis of endogenous CK and GA concentrationsrequired for growth. In contrast, addition of CK or GA at similarconcentrations during the adaptation (pretreatment) period inhibitsgrowth and prevents the adaptation process. The response tothe exogenous phytohormone treatments depends on the time elapsedfrom the beginning of salinization. Key words: Adaptation to salinity, cytokinin, gibberellic acid, mineral nutrition, growth, Sorghum, NaCl     

Rhizobium-stimulated Callose Formation in Clover Root Hairs and its Relation to Infection

Callose was detected in the cell walls of the tips of growingroot hairs of Trifolium species and the non-legume Phleum pratenseusing u.v. fluorescence of fresh material stained with 0·005%aniline blue. Inoculation of the roots with Rhizobium trifolii,R. leguminosarum, R. meliloti, and R. japonicum, or additionof 10^–7 and 10^–8 M indole-3-acetic acid (IAA) increasedtip callose formation. Most tip callose was formed at 12 °C, and amounts declinedprogressively at 18, 24, and 30 °C, with very little formedat 36 °C. Tip calloso usually became less and disappearedin individual root hairs as they aged. Callose which appeared prominently in the host cell walls atthe points of initiation of infection threads did not usuallydisappear as the hairs matured. There was little or no extensionof callose along the infection thread and none in the threadtip or in the cell nucleus. Presumptive regions of callose hadsimilar structure and electron density as root hair wall materialand were sometimes related to arrays of vesicles in the hostcytoplasm. The external surface of the hair wall bore smallpegs or papillae (0·1–0·2 µm) continuouswith the outer layer of the wall and possibly associated withattachment of bacteria. Bacteria were usually umboriate at thepoint of attachment and their polyphosphate granules were muchlarger near the root hair than at the distal end.     

Effects of Temperature and Growth Regulators on Formation of Anlagen, Tendrils and Inflorescences in Vitis vinifera L.

The effects of single, combined and sequential application ofgibberellic acid (GA), chlormequat and cytokinins on the formationof anlagen, tendrils and inflorescences were studied in grapevines(cv. Muscat of Alexandria) grown with natural illumination athigh temperature (30 °C day to 25 °C night) and at lowtemperature (21 °C day to 16°C night or 18 °C dayto 13 °C night). GA promoted the formation of anlagen andgrowth of tendrils regardless of temperature, but inhibitedinflorescence production. Chlormequat had the opposite effecton anlagen formation and tendril growth and promoted inflorescenceformation from pre-formed anlagen or from tendril initials.While low temperature is normally unfavourable for inflorescenceformation, this was induced by chlormequat even at low temperature,but only with summer light conditions. Cytokinin application to plants pre-treated with chiormequatcaused tendrils to grow into inflorescences regardless of temperatureregimes. Moreover, shoot primordia were also formed in place⁸oftendrils in cytokinin treated plants even without chlormequatpre-treatment. Vitis vinifera L., grapevine, gibberellic acid, chlormequat, cytokinins, benzyladenine, inflorescence, tendrils     

The Growth of Shoot Apices and Inflorescences of Carex flacca Schreb. in Aseptic Culture

The vegetative apex and young inflorescence of Carex flaccahave been grown in aseptic culture for several weeks on a definedmedium. Explants comprised the apical dome and the three youngestleaf primordia, and the young inflorescence complete with bracts,excised shortly after the initiation of the lateral spikes.Some growth occurred on the basal medium which contained inorganicsalts, sucrose, and vitamins, but growth was increased and thelife span extended by the addition of certain other compounds.The most effective additive was gibberellic acid, which, however,resulted in precocious differentiation of the meristematic tissuesand the differentiation of abnormal xylem. These deleteriouseffects of gibberellic acid were counteracted by the additionof kinetin. This substance did not otherwise affect vegetativeapices but it resulted in a further increase in growth and lifespan of inflorescences.     

The Germination Characteristics of Tithonia rotundifolia

The achenes of the plant Tithonia rotundifolia show an embryodormancy, requiring a 3-month period of after-ripening to stimulategermination. Mechanical scarification did not enhance imbibitionof the achenes, indicating that the thick bi-layered achenewall does not impede water uptake. The light conditions necessaryfor optimal germination changed with achene age and the achenesbecame less sensitive to temperature. About 30–40% ofrecently harvested achenes germinated in the dark at 25 °C.Following a period of dry storage some of the achenes developeda light requirement and germination increased at 20, 25 and30 °C. Gibberellic acid stimulated the germination of achenestested after 12 weeks dry storage, and could substitute to someextent for the light and temperature requirements of the storedachenes. Tithonia rotundifolia, seed germination, gibberellic acid     

Morphogenetic Potential of Embryo- and Seedling-Derived Callus of Elaeis guineensis Jacq. var. pisifera Becc.

The oil palm of commerce, Elaeis guineensis (tenera), derivesfrom hybridization of variety dura x pisifera. Germ plasm ofpisifera is limited, however, because of varying degrees offemale sterility. Efforts to increase the range of availablepisifera male germ plasm have thus far been limited to fertilepisiferas but it is anticipated that clonal multiplication ofembryos and explanted organs from less female-fertile, but nonethelessfertile, male, plants could play a significant role in breedingprogrammes. Callus has been produced from mature pisifera embryosand leaf explants from young plantlets using a half-strengthMurashige and Skoog medium supplemented with inositol, caseinhydrolysate, activated charcoal and varying concentrations ofauxins. After sub-culture on media of similar composition, organizedstructures can develop. Those which form in stale nutrient media(e.g. left in the same medium for up to 3 months) give riseto embryonal structures which do not readily develop furtherand can be regarded as neomorphs. If callus once formed is transferredto media with lower auxin concentrations (40–0 mg l^–1)embryonal buds and well-formed shoots are produced; additionof gibberellic acid (GA₃) fosters the production of well-organizedshoots accompanied by roots. Elaeis guineensis var pisifera, oil palm, tissue culture, micropropagation, embryo development, morphogenetic potential, callus     

Temperature and photoperiodic control of developmental responses in climatic races of Mimulus

Two strongly differentiated climatic races of the Mimulus cardinalis-lewisiicomplex were grown at a variety of temperatures (3–27°C)and photoperiods (8 and 16 hr) under controlled environmentalconditions. M. cardinalis (the lowland race, 400 m) and M. lewisii(the sub-alpine race, 3200 m) were found to differ in theirphysiological responses to the varied environments in severalsignificant ways: 1) At 27°C (16 hrphotoperiod), M. lewisiisustained 100% mortality in contrast to the substantial growthand flowering of M. cardinalis under these conditions; 2) In8 hr photoperiods at all temperatures, there was little growthand no flowering in M. lewisii whereas there was considerablegrowth at all temperatures, and flowering at 23 and 27°Cin M. cardinalis; 3) At low temperatures (7–15°C),16 hr photoperiods, flowering occurred a week or two earlierin M. lewisii than in M. cardinalis. The lowland race has asignificantly wider temperature and photoperiodic tolerancethan has the sub-alpine race. Applications of gibberellic acidto rosette Mimulus plants under non-inductive conditions (15°C,8 hr photoperiod) promoted vigorous stem elongation withoutflowering. The application of steroids, other hormones and metaboliteshad no observable effects. ¹Present address: Faculty of Botany, Ohio State University,Columbus, Ohio, U.S.A. (Received March 16, 1970; )     

Plant Regeneration Through Meristem Culture from Vegetative Buds of Mulberry (Morus bombycis Koidz.) Stored in Liquid Nitrogen

Intact vegetative buds of mulberry (Morus bombycis) attachedto shoot segments were prefrozen, stored in liquid nitrogen,thawed, and the meristems excised for culture on Murashige andSkoog's medium supplemented with 1 mg 1^–1 BA to regenerateplants. Either prefreezing at –10 °C or –20°C along with rapid thawing at 37 °C or prefreezingat –20 °C or –30 °C along with slow thawingat 0 °C was a suitable condition for high percentages ofsurvival and shoot regeneration. Potted mulberry plants couldbe finally obtained from the cryopreserved material. The systemusing intact buds as the material for cryopreservation is quitesimple when compared to conventional systems using isolatedmeristems together with cryoprotectants. Morus bombycis Koidz., mulberry, cryopreservation, meristem culture, plant regeneration     

Initiation and Growth of Callus and Cell Suspensions of Theobroma cacao L

Callus and suspension cultures of Theobroma cacao L., initiatedfrom immature cotyledons of beans from pods harvested 120–130days after pollination were established. A modified B-5 or Murashige—Skoogagar medium sustained growth of callus without loss of vigourafter each sub-culture. A 15-fold weight increase occurred duringthe 4 week culture periods at 30 ± 1 °C. Coconutwater improved callus growth substantially. The optimum hormonalconcentrations for growth of suspensions were 0.5 mg 1^–1of 2, 4-dichlorophenoxyacetic acid and 0.1 mg I^–1 of kinetinin a Murashige—Skoog basal medium liquid medium. The optimumtemperature for growth of suspensions was 25–30 °C.The cell number and cell mass of suspensions increased 20-foldin 14 days. No organogenesis or embryogenesis was observed. Theobroma cacao L., acao, cell culture, suspension culture, tissue culture.     

Sporulation in Rhizopus sexualis and Some Other Fungi Following a Period of Intense Respiration

Rhizopus sexualis grown at 20° C. on liquid I per cent.malt or glucose-asparagine medium showed a peak of respiratoryactivity between 40 and 55 hours-after inoculation. Rate ofrespiration then fell until it reached a steady low level whichcoincided with maximum mycelial growth. Zygospore initiationoccurred at or just after the peak of respiration. At a low temperature (9° C.) or with high concentrationsof glucose the respiration peak was less marked and no zygosporesdeveloped. Single ‘plus’ or ‘minus’strains of the heterothallic species Mucor hiemalis and Phycomycesblakesleeanus showed a pattern of respiration and mycelial growthsimilar to that of R. sexualis but no zygospores were formed.Zygospores did not develop without a preliminary period of intenserespiration, but such a peak period could occur without beingfollowed by zygospore formation. A strain of Sordaria fimicola was grown at 25° C. on a syntheticmedium with 5.0 per cent. sucrose or glucose as source of carbon.Respiration reached a peak at approximately 4 and 5 days respectively,the actual peak value being twice as large on sucrose as onglucose. Dry weight of mycelium was greater on glucose thanon sucrose. Perithecia were formed only on the sucrose medium.Visible peri-thecial initials were first seen shortly afterthe occurrence of the respiratory peak. Mature perithecia werepresent 3 days later. The possible significance of these results is discussed.     

Temperature and photoperiodic control of developmental responses in climatic races of Achillea

Three climatic races of Achillea from central California (20,1400 and 3100 m elevation) were grown under controlled environmentalconditions at 14 combinations of temperature (0–27°C)and photoperiod (8 or 16 hr). Periodic measurements were madeon height and flowering. Dry weights of roots and shoots ofmature plants were determined. The greatest growth in heightand weight for each race occurred at 11°C on long days (16hr). The coastal race (20 m) grew well over a wide range oftemperatures (7–27°C) but the higher elevation races(1400 and 3100 m) grew well only at low temperatures (7–15°C).In contrast to the vigorous elongation and flowering of thecoastal race in short days at nearly all temperatures, racesfrom the higher elevations remained as rosettes. The sub-alpinerace (3100 m) exhibited the highest root-shoot ratios. Floweringpreceded stem elongation in the sub-alpine race but followedstem elongation in the coastal race. Exogenous applicationsof gibberellic acid (500 mg/liter) to rosette high-elevationraces promoted stem elongation and some flowering. Steroid applicationshad little or no effects. The high-elevation races may containa high-temperature sensitive control mechanism for gibberellinproduction. ¹Present address: Faculty of Botany, Ohio State University,Columbus, Ohio, U. S. A. (Received March 7, 1970; )     

The Effect of Gibberellic Acid on Starch Breakdown in Sprouting Tubers of Solanum tuberosum L.

The treatment of potato tubers with 150 µmol dm^–3gibberellic acid (GA₃) stimulated starch breakdown and hexoseaccumulation in tuber tissues and the transfer of dry matterto stems. These effects could not be accounted for by enhancedactivities of starch phosphorylase, amylase and acid invertase.Indeed enzyme activities either declined or remained relativelyconstant as starch degradation and hexose accumulation proceeded.Changes in the rate of starch depletion were related to changesin sink strength and sink type, the onset of tuber initiationin controls causing the rate of starch degradation to exceedthat in GA₃-treated tissues, in which tuberization was inhibited. Solanum tuberosum L., gibberellic acid, starch breakdown     

Germination of seeds in Hyptis suaveolens Poit

Seeds of Hyptis suaveolens require long illumination periodsto promote full germination, both light and dark germinationbeing controlled by the phytochrome system. Germination in thisspecies is inhibited both by relatively low (up to 20°C)and high temperatures (45°C). Experiments in which seedswere transferred after different periods from sub-optimal orsupra-optimal temperatures to a favourable one, suggest thatboth high and low temperature inhibition may be explained onthe basis of phytochrome action. Thus, a temperature of 20°Cinduces dark dormancy due, probably, to dark reversion of phytochrometo the inactive form; whereas, at 45°C the dominant processseems to be phytochrome decay. No phytochrome loss has beenobserved at 10°C. If, however, phytochrome levels are reducedby a particular treatment, no irreversible alteration is produced;seeds simply require longer illumination periods under diesecircumstances. A low initial concentration of phytochrome couldaccount for the requirement of long illumination periods. Other factors affecting germination in this species, such asalternating temperatures, gibberellic acid and time of storage,are discussed. ¹ Present address: Instituto Venezolano de Investigaciones Cientificas,Apartado 1827, Caracas, Venezuela. (Received January 21, 1971; )     

Requirement of sodium chloride for the action of gibberellic acid in stimulating hypocotyl elongation of a halophyte, Salicornia herbacea L.

NaCl stimulated hypocotyl elongation of the halophyte Salicorniaherbacea L. grown either in light or dark. Its optimal concentrationwas around 0.1–0.2 M and its promoting effect was muchmore prominent in the dark. Gibberellic acid at 10^–5 Mstimulated hypocotyl elongation in light but not in the dark.Indole-3-acetic acid and kinetin were ineffective in promotinghypocotyl elongation. In light, gibberellic acid and NaCl synergisticallyenhanced hypocotyl elongation when both were given simultaneously.The action of NaCl could be replaced by KCl, but not by mannitol.Osmotic pressure of the epidermis of the Salicornia hypocotylincreased in response to gibberellic acid and/or NaCl treatment.Na⁺ content in the hypocotyl increased with NaCl application.Gibberellic acid and NaCl when given alone increased the extensibilityof the hypocotyl cell wall. Synergistic interaction in increasingthe extensibility was observed between gibberellic acid andNaCl. Stress-relaxation analysis of mechanical properties ofthe hypocotyl wall revealed that gibberellic acid and NaCl actedsynergistically in decreasing minimum relaxation time. Basedon these results, a possible mechanism by which gibberellicacid and NaCl regulate hypocotyl elongation of Salicornia herbaceaL., a typical halophilic plant, is discussed. ¹ Present address: Laboratory of Biology, Tezukayama College,Gakuen Minami, Nara 631, Japan. (Received June 13, 1978; )     

Effect of nucleic acid antimetabolites on the vernalization of winter wheat

Excised winter wheat embryos were cold-treated in White's mediumcontaining 2% sucrose for 60 days at 4°C. Embryos couldbe vernalized in medium containing sugar, whereas the additionof 8-azaguanine to the medium at the concentration of 10^–4M inhibited vernalization. (Received May 2, 1975; )     

Influence of Environmental Stress on the Germination of Anabaena vaginicola Akinetes

Germination of akinetes of Anabeana vaginicola v. fertilissimaPrasad in response to environmental stress was studied. Additionof nitrate to the medium induced early and maximum germination(96 per cent), whereas less than half of the akinetes germinatedwhen either nitrate or phosphate was omitted from the medium.The pH range over which germination occurred was 7.0–9.0.The desiccated akinetes after rehydration germinated after acertain lag period, depending upon the dehydration state. Thetemperature optimum for germination and vegetative growth wasthe same (25 °C) and germination did not occur at 5 °Cor above 35 °C. The limit of heat shock tolerated was 55°C for 4 min. In addition to white light, only the red partof the visible spectrum induced germination. Ultraviolet radiationreduced germination rate presumably by inducing thymine dimersin DNA. The photoreactivating system (s) in akinetes is certainlynon-photosynthetic. LD₅₀ photon flux densities were 300 Jm^–2for akinetes and 240 Jm^–2 for vegetative cells. Anabaena vaginicola, blue-green alga, akinete, germination, environmental stress     

The Effect of Temperature and Light on Gas Exchange and Acid Accumulation in the C3-CAM Plant Clusia minor L

Gas exchange and organic acid accumulation of the C₃-CAM intermediateClusia minor L. were investigated in response to various day/nighttemperatures and two light regimes (low and high PAR). For bothlight levels equal day/night temperatures between 20°C and30°C caused a typical C₃ gas exchange pattern with all CO₂uptake occurring during daylight hours. A day/ night temperatureof 15°C caused a negative CO₂ balance over a 24 h periodfor low-PAR-grown plants while high-PAR-grown plants showeda CAM gas exchange pattern with most CO₂ uptake taking placeduring the dark period. However, there was always a considerablenight-time accumulation of malic acid which increased when thenight-time temperature was lowered and had its maximum (54 mmolm^–2) at day/night temperature of 30/15°C. A significantamount of malic acid accumulation (23 mmol m^–2) in low-PAR-grownplants was observed only at 30/15°C. Recycling of respiratoryCO₂ in terms of malic acid accumulation reached between 2·0and 21·5 mmol m_–2 for high-PAR-grown plants whilethere was no significant recycling for low-PAR-grown plants.Both low and high-PAR-grown plants showed considerable night-timeaccumulation of citric acid. Indeed under several temperatureregimes low-PAR-grown plants showed day/night changes in citricacid levels whereas malic acid levels remained approximatelyconstant or slightly decreased. It is hypothesized that lowand high-PAR-grown plants have different requirements for citrate.In high-PAR-grown plants, the breakdown of citrate preventsphotoinhibition by increasing internal CO₂ levels, whereas inlow-PAR-grown plants the night-time accumulation of citric acidmay function as an energy and carbon saving mechanism. Key words: C. minor, C₃, CAM, citric acid, light intensity     

Germination responses of <Emphasis Type="Italic">Erica andevalensis</Emphasis> to different chemical and physical treatments

Erica andevalensis Cabezudo & Rivera is a threatened edaphic endemic species of Andalusia (SW Spain). Under natural conditions, the plants produce a very large number of small seeds (0.3–0.4 mm) but very few seedlings survive. Different treatments (high temperature, cold pre-treatment, nitrogen salts, and gibberellic acid applications) were tested to assess germination patterns in different populations and to determinate the most favorable conditions for germination. Gibberellic acid was provided in five different concentrations from 0 to 400 ppm GA₃, while nitrogen was applied as 10 mM of either KNO₃ or NH₄NO₃. The effect of pH on germination was also tested. The species always showed a low germination rate (6.50–22%) that was not stimulated either by 1 or 4 months in dry cold pre-treatment, nitrogen application, acid pH medium, or by high temperature (80°C for 10 min); although gibberellic acid application (100–400 ppm) significantly enhanced germination. The highest percentage of germination (41.6%) was achieved with a mean germination time to start germination (t ₀) of 7.6 ± 0.54 days when the seeds were subjected to 400 ppm gibberellic acid treatment. The population origin did not have a significant effect on germination percentage.     

Effect of Ethylene and Culture Environment on Rice Callus Proliferation

Modifications to the gaseous envelope by callus during culturein Petri dishes were shown to reduce growth and promote necrosisof several rice (Oryza sativa L.) cultivars. Incubatingcallusunder a continuous flow of gas mixtures of known compositionsuggested that the inhibition of growth was caused by the accumulationof ethylene, the depletion of oxygen and, to a lesser extent,the accumulation of carbon dioxide. In order to evaluate theimportance of ethylene accumulation aminoethoxyvinylglycine(AVG), 1-aminocyclopropane-l-carboxylic acid (ACC and silvernitrate (AgNO₃), were added to the nutrient medium and ethylenemeasurements performed during callus culture. Ethylene restrictedcallus growth particularly under high (35 °C) as comparedto moderate (25 °C) temperatures and under illuminated ascompared to darkened incubation. Under illuminated incubationat 25 °C AVG (5 mmol m^–3) and AgNO°(50 mmol m^–3)significantly improvedcallus growth (100 and 60% respectively)while ACC (200 mmol m^–3) significantly decreased growth(40%). AVG and AgNO₃ were less effective under dark incubationat 25 °C where ethylene production was lower. Furthermore,callus growth was significantly better in large as comparedto small culture vessels since the ethylene concentration wasdiluted and more oxygen was available for respiration. Bettercontrol of ethylene and increased oxygen availability couldbe a way ofproducing healthy callus for the formation of embryogenictissues of otherwise recalcitrant cultivars of rice (e.g. IndicaIR42) and may be a way of improving manipulation of other cerealspecies. Key words: 1-Aminocyclopropane-1-carboxylic acid, aminoethoxyvinylglycine, callus, ethylene, Oryza sativa, silver nitrate