Geotropic Responses and Pod Development in Gynophore Explants of Peanut (Arachis hypogaea L.) Cultured In Vitro

Peanut gynophore explants cultured in vitro on a defined mediumshow a positive geotropic response in both light and dark whenplanted either horizontally, or vertically with the tip pointingupwards. The growth following the initial curvature dependedon age of the gynophores and on the levels of growth substancesin the medium. In the dark and in presence of 0·01–0·1p.p.m. kinetin, naphthalene acetic acid at concentrations of0·1 p.p.m. and lower promoted gynophore elongation. Athigher concentrations elongation was promoted to a lesser extentin younger explants, caused enlargement of the ovary and formationof pods. Young explants generally elongated more than olderones and pod formation took place inside the medium, while inolder ones it took place above the medium. In the light, theinitial positive geotropic response was followed by elongationbut without any enlargement of the ovary. Decapitation of gynophores1·5–2·0 mm below their tip, removing theovary but leaving most of the intercalary meristem, had no effecton the geotropic response and elongation. The initial geotropicresponse and elongations of explants in vitro was not dependenton the presence of the ovary but on the meristem proximal toit. Changes in growth substances balance during gynophore developmentseem to affect geotropic response, elongation and pod formationin the peanut.     

Light,dark and growth regulator involvement in groundnut (Arachis hypogaea L.) pod development

Gynophore elongation and pod formation were studied in peanut plants (Arachis hypogaea L.) under light and dark conditions in vivo. The gynophores elongated until pod formation was initiated. Pod (3–20 mm length) development could be totally controlled by alternating dark (switched on) and light (switched off) conditions, repeatedly. Gynophore elongation responded conversely to light/dark conditions, compared to pods. In this study we aimed to correlate the light/dark effects with endogenous growth substances. The levels of endogenous growth substances were determined in the different stags of pod development. Gynophores shortly after penetration into the soil, ‘white’ gynophores, released twice the amount of ethylene as compared to the aerial green ones, or to gynophores bearing pods. Ethylene inhibitors had no effect on the percent of gynophores that developed pods, but affected pod size which were smaller compared to the control. A similar level of IAA was extracted from gynophore tips of green gynophores, ‘white’ gynophores and pods. ABA levels differed between the three stages and were highest in the green gynophores and lowest in the pods.     

Pod development of groundnut (Arachis hypogaea L.) in solution culture

Normal pods (containing seed) of groundnut (Arachis hypogaea L.) (cv. TMV-2) were successfully raised in darkened, aerated, nutrient solution, but not in the light. The onset of podding was evident 7 to 8 d after gynophores were submerged in the darkened nutrient solution. An examination of pods and submerged portions of gynophore surfaces by scanning electron microscopy showed the presence of two distinctly different protuberances: unicellular root-hair-like structures that first developed from epidermal cells of the gynophores and developing pods; and branched septate hairs that developed later from cells below the epidermal layer. The septate hairs became visible only after the epidermal and associated unicellular structures had been shed by the expanding gynophore and pods. Omission of Mn and Mg from the podding environment increased pod and seed weight, whilst omission of Zn reduced pod and seed weight.     

Initiation and Morphogenesis of Groundnut (Arachis hypogaeaL.) Pods in Solution Culture

A recently-developed solution culture technique was used tostudy the effects of aeration and calcium (Ca) on groundnut(ArachishypogaeaL.) pod development. Two experiments were conductedwith seven groundnut lines, TMV-2, Chico and A116L4 (Spanish),CBRR4 (Valencia), A125L25 (ValenciaxSpanish), and Shulamit Strain1 (SH-1) and Virginia Brunch Strain 1 (VB-1) (Virginia). Plantswere grown in a potting mix, and the attached gynophores culturedin darkened polycarbonate jars containing nutrient solution.Non-aeration of solution prevented pod development, but podsand seeds of all lines developed in aerated, darkened nutrientsolutions (ionic strength approx. 9 mM). Normal pods and seedswere produced by TMV-2, Chico and CBRR4, but constricted podsdeveloped in SH-1 and VB-1. A secondary gynophore developedbetween the basal and apical seed compartments in A116L4 andA125L25, and in VB-1 at high Ca (500–2500 µM) insolution. The secondary gynophores were similar to those producedin otherArachisspp. but not usually found in cultivated formsofA. hypogaea.Septate and non-septate hairs developed on submergedgynophores and pods, but were sparse on those of SH-1 and VB-1.The magnitude of the effects of aeration and Ca concentrationon pod initiation and morphogenesis differed in experimentsconducted in summer and winter and among the lines tested.Copyright1998 Annals of Botany Company Arachis hypogaeaL., calcium, groundnut, pod morphology, secondary gynophore, solution culture.     

Pod Formation and Its Geotropic Orientation in the Peanut, Arachis hypogaea L., in Relation to Light and Mechanical Stimulus

Gynophore elongation, pod formation and pod orientation in thepeanut plant (Arachis hypogaea L.) were studied in relationto the effects of light and dark conditions, mechanical stimulus,and growth substances. It was found that the proembryos controlgynophore elongation, probably by secretion of growth regulatorswhich stimulate cell division in the intercalary meristem locatedproximal to the ovules. The stimulus of pod production causesthe development of the proembryo into a mature embryo simultaneouslywith the growth of pod tissues and the cessation of gynophoreelongation. Darkness was found to be an essential factor forthe induction of pod formation. Pod formation did not occurin any of the treatments performed in the light, including theapplication of different growth substances on the ovary. A mechanicalstimulus is needed, in addition to darkness, for the normalthickening and diageotropic orientation of the pod, caused bya higher growth rate of the basal proximal side of the pod.The two ovules are always located on the upper wall of the diageotropicallyoriented pod (ventral suture). A possible mechanism which causessuch an orientation is discussed.     

Light, dark and growth regulator involvement in groundnut (Arachis hypogaea L.) pod development

Gynophore elongation and pod formation were studied in peanut plants (Arachis hypogaea L.) under light and dark conditions in vivo. The gynophores elongated until pod formation was initiated. Pod (3–20 mm length) development could be totally controlled by alternating dark (switched on) and light (switched off) conditions, repeatedly. Gynophore elongation responded conversely to light/dark conditions, compared to pods. In this study we aimed to correlate the light/dark effects with endogenous growth substances. The levels of endogenous growth substances were determined in the different stags of pod development. Gynophores shortly after penetration into the soil, white gynophores, released twice the amount of ethylene as compared to the aerial green ones, or to gynophores bearing pods. Ethylene inhibitors had no effect on the percent of gynophores that developed pods, but affected pod size which were smaller compared to the control. A similar level of IAA was extracted from gynophore tips of green gynophores, white gynophores and pods. ABA levels differed between the three stages and were highest in the green gynophores and lowest in the pods.Abbreviations ABA abscisic acid - AOA aminooxyacetic acid - ELISA enzyme linked immunosorbent assay - Ethrel 2-chloroethanephosphonic acid - GC gas chromatography - HPLC High Performance Liquid Chromatography - IAA indole-3-acetic acid - NAA naphthalene acetic acid - RIA radioimmunoassay - STS silver thiosulfhate - TIBA 2,3,6-triiodobenzoic acid     

Growth and Dormancy in Lunularia cruciata (L.) Dum.: III. THE WAVELENGTHS OF LIGHT EFFECTIVE IN PHOTOPERIODIC CONTROL

Growth and dormancy in Lunularia are controlled by daylength,short-day promoting active growth, long-day or light-break treatmentinducing dormancy. Light-breaks of red light are highly effectivein inducing dormancy, while irradiation with other wavebandsis much less inhibitory to growth. Far-red light given afterred irradiation causes substantial reversal of the red-lighteffect, suggesting strongly that phytochrome is involved inthe photoperiodic response mechanism of Lunularia. However,even short(15 sec.) exposures to far-red light alone cause significantgrowth inhibition, and it is considered possible that far-redirradiation also leads to the formation of some of the P 730form of phytochrome.     

Dark transformations of phytochrome in cotyledons of Pharbitis nil

Pharbitis seedlings grown in total darkness or continuous far-redirradiation were exposed to 30 min of red irradiation followedby a dark period, and in vivo phytochrome in their cotyledonswas photometrically assayed at various times. Loss of photo-reversibilityof P_fr after the exposure to red light occurred without darkreversion to P_r in cotyledons of both seedlings. P_fr decay inthe former cotyledons was mostly prevented in the first 30 minunder red light illumination, while that in the latter occurredwithout such a lag phase. P_fr was no longer photometricallydetectable by the eighth hr after irradiation at both 18?C and25?C. No evidence has yet been obtained to show a correlation betweenphotometrically detectable phytochrome in vivo and the red far-redreversible responses of flowering. (Received August 6, 1974; )     

Measurement of the Critical Nyctoperiod by Lemna paucicostata 6746 Grown in Continuous Light

The short-day duckweed Lemna paucicostata 6746 could be inducedto flower in two days at 26C when continuous illumination forentrainment was followed by continuous darkness. This 48-h darkperiod or the minimum darkness requirement for floral inductionwas called the induction period. The length of the inductionperiod (IP) was routinely computed as the number of 24-h cyclesusing the equation of regression of flower number in logarithmon culture time. A light pulse given about 7 h after the startof the induction period increased the apparent IP value fromtwo to three, suggesting that the interrupted first day hadfunctioned as a noninductive day. A pulse given at any otherpart of the induction period did not modify the IP value. Thelight-sensitive part is probably the inducible phase, and thefirst 7-h period of darkness terminated by it seems to be thecritical nyctoperiod. These and relevant facts suggest thatthe light-off oscillator measures the critical night length,7 h. Either red or far-red irradiation at the inducible phase extendedthe IP value by one. No red/far-red photoreversibility was detected.As expected, however, red or far-red irradiation of any otherpart of the critical nyctoperiod could not modify the IP value. (Received February 8, 1985; Accepted May 14, 1985)     

Light germination ofAnthoceros miyabeanus spores

The effects of light on the spore germination of a hornwort species,Anthoceros miyabeanus Steph., were investigated. Spores of this species were photoblastic, but their sensitivities to light quality were different. Under either continuous white, red or diffused daylight, more than 80% of the spores germinated, but under blue light none or a few of them germinated. Under continuous far-red light or in total darkness, the spores did not germinate at all.Anthoceros spores required red light irradiation for a very long duration, i.e., over 12–24 hr of red light for saturated germination. However, the spore germination showed clear photo-reversibility by repeated irradiation of red and far-red light. The germination pattern clearly varied with the light quality. There were two fundamental patterns; (1) cell mass type in white or blue light: spores divide before germination, and the sporelings divide frequently and form 1–2 rhizoids soon after germination, and (2) germ tube type in red light: spores germinate without cell division, and the single-cell sporelings elongate without cell division and rhizoid formation.     

Phytochrome Control of Turion Formation in Spirodela polyrhiza L. Schleiden

Turion yield in Spirodela polyrhiza, strain SJ, is increasedby increasing the daily light period. This effect is more pronouncedin autotrophic than in mixotrophic conditions. Night-break irradiation(15 mins) increased turion yield by 150 % under the conditionsof an 8-h daily light period. Besides the effect of night-breakirradiation, end-of-day far-red irradiation decreased turionyield with increasing photoperiod, whereas end-of-day red irradiationwas without any effect. This demonstrates the promoting effectof the P_fr form of phytochrome on formation of light-grown turions. Formation of dark-grown turions was increased by about 240%by a single red light pulse and was reversed by an immediatelyapplied far-red light pulse. Consequently, under heterotrophicconditions phytochrome modulates the turion formation process. Spirodela polyrhiza L. Schleiden, duckweed, Lemnaceae, photomorphogenesis, phytochrome, turion     

The relationship between red and far-red light on flowering of the long-day plant, Lemna gibba

Lemna gibba, a long-day duckweed, can be induced to flower whenthe 10 hr white photoperiod is extended with red or far-redlight. The 10 hr red photoperiod is also effective in inducingflowering when followed by a far-red extension, but a red extensionis ineffective. When 2 hr of far-red light are given immediately after the 10hr red photoperiod, the following red as well as the far-redextension can induce flowering, indicating that the 2 hr far-redlight plays an important role as a starting factor for induction.This red or far-red extension is effectively replaced by a redbreak given at a proper time in the darkness which follows the2 hr far-red light as the starting factor. The effect of thered break in not cancelled by subsequent exposure to far-red,which synergistically promotes flowering. However, a red break given immediately after a proper periodof far-red extension further promotes flowering. The phase sensitiveto the red break coincides with that sensitive to the red breakgiven in darkness. The effect of the red break is reversed bysubsequent exposure to far-red, contrary to the effect of thered break in darkness. Using these results, relation between red and far-red lighton flowering in L. gibba is discussed. (Received July 17, 1971; )     

PHOTOMORPHOGENESIS IN PTERIS VITTATA: I. PHYTOCHROME-MEDIATED SPORE GERMINATION AND BLUE LIGHT INTERACTION

1. Spores of the fern Pteris vittata did not germinate under totaldark conditions, while an exposure of the spores to continuouswhite light brought about germination. The germination was mosteffectively induced by red light and somewhat by green and far-red,but not at all by blue light. The sensitivity of spores to redlight increased and leveled off about 4 days after sowing at27–28. The promoting effect of red light could be broughtabout by a single exposure of low intensity. Far-red light givenimmediately after red light almost completely reversed the redlight effect, and the photoresponse to red and far-red lightwas repeatedly reversible. The photoreversibility was lost duringan intervening darkness between red and far-red irradiations,and 50% of the initial reversibility was lost after about 6hr of darkness at 27–28. These observations suggest thatthe phytochrome system controls the germination of the fernspore.
2. When the imbibed spores were briefly exposed to a low-energyblue light immediately before or after red irradiation, theirgermination was completely inhibited. The blue light-inducedinhibition was never reversed by brief red irradiation givenimmediately after the blue light. The escape reaction of redlight-induced germination as indicated by blue light given aftervarious periods of intervening darkness was also observed, andits rate was very similar to that determined by using far-redlight. Spores exposed to blue light required 3 days' incubationin darkness at 27–28 to recover their sensitivity tored light. The recovery in darkness of this red sensitivitywas temperature-dependent. It is thus suggested that an unknownbluelight absorbing pigment may be involved in the inhibitionof phytochrome-mediated spore germination.

(Received August 21, 1967; )     

Phytochrome Control of Chlorophyll and Carotenoid Accumulation in Sorghum bicolor

Etiolated Sorghum bicolor seedlings manifested a significantmorphological response to short term irradiations by red andfar-red light and to a continuous far-red light. Accumulationof chlorophylls in white light and carotenoids in darkness isunder red/far-red reversible control as well as along with theeffectiveness of ‘High Irradiance Reaction’. Phytochromeis also found to eliminate the lag phase during the accumulationof chlorophylls and carotenoids in white light. (Received March 11, 1981; Accepted May 2, 1981)     

Photoregulation of seed germination of wild-type and of an aurea-mutant of tomato

Seed germination of an aurea mutant of tomato ( Lycopersicon esculentum Mill.) is promoted by continuous irradiation with red, far-red or long-wavelength far-red (758 nm) light as well as by cyclic irradiations (5 min red or 5 min far-red/25 min darkness). Far-red light applied immediately after each red does not change the germination behaviour. Seed germination of the isogenic wild-type, cv. UC-105, is promoted by continuous and cyclic red light while it is inhibited by continuous and cyclic far-red light and by continious 758 nm irradiation. Far-red irradiation reverses almost completely the promoting effect of red light. The promoting effect (in the aurea mutant) and the inhibitory effect (in the wild-type) of continuous far-red light do not show photon fluence rate dependency above 20 nmol m⁻² s⁻¹. It is concluded that phytochrome controls tomato seed germination throgh low energy responses in both the wild type and the au mutant. The promoting effect of continuous and cyclic far-red light in the au mutant can be attributed to a greater sensitivity to P_fr.     

Different actions of red and blue or far-red lights in the photoperiodic tuberization of Begonia evansiana

The spectral dependence of Begonia evansiana in supplementarylight periods of photoperiodic tuberization and sprouting wasinvestigated. Supplementary application of red light inhibitedtuber development, thereby stimulating vegetative growth. Supplementaryblue or far-red light also suppressed tuber development, butbarely stimulated vegetative growth. However, both red and blue light, given at 6°C during themain light period or the supplementary light period, permittedthe tuberization under the subsequently given conditions ofeither long-days or darkness at 23°C. Blue light appliedafter 5-days of irradiation with white light at 10°C, showedalmost the same action as far-red light, which suppressed tuberizationin darkness. The nature and function of the pigments concernedin the photoperiodic responses are discussed. (Received October 11, 1968; )     

Phytochrome-mediated germination control of maize caryopses

Maize caryopses sown in water germinate equally well either in darkness or under any light regime. However, when they are imbibed in mannitol solutions, continuous far-red light proves to be strongly inhibitory on the final germination as compared to darkness. Similar but less pronounced inhibition is also exhibited by continuous red or blue light. Intermittent far-red light can partially substitute for continuous far-red light in inhibiting maize caryopsis germination, and its effect is reversed to the intermittent red light level when red light is given immediately after each far-red illumination. These results are interpreted as a proof of existence and involvement of phytochrome in the germination control of maize caryopses, though its manifestation is realized only under osmotic stress.Abbreviations D darkness - FR far-red - R red - B blue - c-FR, c-R, c-B continuous FR, R, B, resp. - i-FR, i-R intermittent FR, R, resp.     

Kinetic Study on the Development of the Capacity to Accumulate Chlorophyll A without a Lag Phase during Continuous Far-Red Irradiation in Pharbitis nil Seedlings

To analyze how the capacity to accumulate chlorophyll a (Chia) without a lag phase develops by continuous far-red light(FR) irradiation, the time course of the capacity was investigatedunder various FR-dark conditions in Pharbitis seedlings. Thecapacity, which is negligible in darkness, rapidly developedon transfer to continuous FR irrespective of the age of theseedlings, the maximum level being attained about 18-24 h afterthe onset of.FR irradiation. The-capacity gradually decreasedthereafter whether in darkness or under extended FR irradiation.When the seedlings pretreated by 6-12 h of FR followed by 66-60h darkness (which have no capacity) were exposed to the secondFR irradiation for up to 72 h, the level of the capacity acquiredduring the second FR irradiation was the lower the higher thelevel acquired by the first FR irradiation. A possible mechanismwhich determines the time course of the development of the capacityis discussed. (Received July 2, 1990; Accepted March 25, 1991)     

Effects of Colchicine and Light on Cell Form in Fern Gametophytes. Implications for a Mechanism of Light-induced Cell Elongation

Spores of the fern, Onoclea sensihilis L., suffer a disruption of normal development when they are cultured on media containing colchicine. Cell division is inhibited, and the spores develop into giant spherical cells under continuous white fluorescent light. In darkness only slight cell expansion occurs. Spherical cell expansion in the light requires continuous irradiation. Photosynthesis does not seem to be involved, since variations in light intensity do not affect the final cell diameter; the addition of sucrose to the medium does not permit cell expansion in darkness; and the inhibitor DCMU does not block the light-induced cell expansion. Continuous irradiation of colchicine-treated spores with blue, red or far-red light produces different patterns of cell expansion. Blue light permits spherical growth, similar to that found under white light, whereas red and far-red light promote the reestablishment of polarized filamentous growth. Although ethylene is unable to induce polarized cell expansion in colchicine-treated spores in darkness or white and blue light, it enhances filamentous growth which already is established by red or far-red irradiation. Both red and far-red light increase the elongation of normal filaments (untreated with colchicine) above that of dark-grown plants, but under all 3 conditions the rates of volume growth are identical. Light, however, does cause a decrease in the cell diameters of irradiated filaments. These data are used to construct an hypothesis to explain the promotion of cell elongation in fern protonemata by red and far-red light. The model proposes light-mediated changes in microtubular orientation and cell wall structure which lead to restriction of lateral cell expansion and enhanced elongation growth.     

The Effects of Red, Far-red, and Blue Light on the Geotropic Response of Coleoptiles of Zea mays

The effects of red, far-red, and blue light on the geotropicresponse of excised coleoptiles of Zea mays have been investigated.Seedlings were grown in darkness for 5 or 6 days, exposed tovarious light treatments, and then returned to darkness fordetermination of the geotropic response. The rate of response of the coleoptiles is decreased after theyhave been exposed to red light (620–700 mµ, 560ergs cm^–2sec^–1 for the 24 hrs, but not for the 4hrs, preceding stimulation by gravity. Furthermore, their rateof response is greatly reduced if they are exposed to red lightfor 10 min and then returned to darkness for 20 hrs before geotropicstimulation. At 25° C an interval of 6 to 8 hrs elapses between a 10-minexposure to red light and the first detectable decrease in thegeotropic response of the coleoptile. This interval can be lengthenedby exposing the seedlings to low temperatures (0° to 2°C) after the light treatment but cannot be greatly shortenedby increasing the duration of exposure to red light. Using a standard procedure of exposing 5-day-old etiolated seedlingsto light for various times, replacing them in darkness for 20hrs and then determining the response of the coleoptiles to4 hrs geotropic stimulation, it has been found that: (a) Exposureto red light for 15 sec significantly decreases the geotropiccurvature of the coleoptiles and that further reduction occurson increasing the length of the light treatment to 2 and 5 min.(b) Far-red light has no effect on the geotropic response ofthe coleoptiles but it can completely reverse the effect ofred light. After repeated alternate exposure to red and far-redlight the geotropic response of the coleoptile is determinedby the nature of the last exposure, (c) Complete reversal ofthe effect of red light by far-red radiation only occurs whenexposure to far-red follows immediately after exposure to red.The reversing effect of far-red radiation is reduced if a periodof darkness intervenes between the red and far-red light treatments,and is lost after a dark interval of approximately 2 hrs. The effect of red light on the rate of geotropic response ofthe coleoptiles is independent of their age and length at thetime of excision. Blue light acts in a similar way to red light, but the seedlingsare less sensitive to blue than to red light. Coleoptiles grown throughout in a mixture of continuous, weak,red, and far-red light have a lower rate of geotropic responsethan etiolated coleoptiles.