Intracellular Transport and Elimination of Resin from Epithelial Duct-cells of Pinus halepensis

The ultrastructure of the resin secreting cells of root ductsof young Pinus halepensis seedlings was studied. It is suggestedthat the endoplasmic reticulum (ER) in addition to taking partin resin synthesis also plays a role in transporting the resinfrom the plastids, mitochondria and nuclear envelope to theplasmalemma. By fusing with the plasmalemma the ER releasesthe resin to the outside of the protoplast. The resin producedin the ground cytoplasm and by the Golgi apparatus seems tobe eliminated by plasmalemma invaginations. Pinus halepensis, resin secretion, root ducts, endoplasmic reticulum     

Ultrastructure of Resin Ducts in Pinus halepensis Development, Possible Sites of Resin Synthesis, and Mode of its Elimination from the Protoplast

Development of the resin duct cavity, sites of resin synthesisin the epithelial cells and elimination of resin from the protoplastwere studied in roots of young Pinus halepensis seedlings. Itis suggested that the Golgi bodies are involved in dissolutionof the middle lamella in the region of the future duct cavityby secretion of lytic enzymes into the cell walls. In earlystages of duct development osmiophilic droplets were observedin plastids, periplastidal and cytoplasmic ER, Golgi vesicles,mitochondria, nuclear envelope and in the cytoplasm. In thelatter they were often observed to be surrounded by a membrane.Electron micrographs suggested that elimination of resin dropletsfrom the protoplast occurs by their becoming surrounded by plasmalemmainvaginations.     

The Relationship between the Growth of the Primary Leaf and of the Coleoptile in Seedlings of Avena and Triticum

Partial inhibition of extension growth of the primary leaf occurswhen whole Triticum seedlings are immersed in aerated solutionsof IAA but is replaced by growth promotion when sucrose is addedto the external solution. In seedlings in which the coleoptilehas been excised, IAA increases the growth of the leaf bothwith and without additional sucrose. Inhibition of the leaf by moderate concentrations of IAA nolonger occurs when the seedling is detached from the endosperm.Sucrose added to the external solution raised the percentageelongation of the coleoptile almost to the level of that attainedin intact seedlings without additional carbohydrate. It alsoenabled the leaf to show a positive growth response with IAA. The results indicate that in intact seedlings treated with IAAthe growth of the primary leaf is markedly diminished owingto diversion of carbohydrate to the coleoptile if the growthof the latter is promoted as a result of the treatment. Whenthe competition of the coleoptile for carbohydrate is diminishedor eliminated, acceleration of the growth of the primary leafby IAA becomes apparent. In addition to the endogenous rhythm, with a period close to24 hours, induced in the growth-rate of the coleoptile whenseedlings of Avena are transferred from red light to darkness,a similar rhythm, with a slightly longer period, is inducedin the growth-rate of the primary leaf. This rhythm persistsin elongating leaves so long as they remain within the coleoptile.It can be recorded for at least 100 hours in deseeded seedlings. When intact seedlings of Avena are immersed for one hour inrelatively high concentrations of IAA and then transferred todistilled water for 18 hours, the elongation of the coleoptileis greater and the inhibition of the leaf is less than whenthey are transferred to humid air. Sections of the leaf of Triticum showed a slight increase inelongation in concentrations of IAA up to 5 mg./l., but no evidencewas obtained that sections of leaf and coleoptile exert any.influenceon each other's elongation when floated together on solutionsof IAA.     

Mobilization of Reserves and Synthesis of Sterols and Triterpenes in Seedlings of Two Canarian Euphorbia Species

Seedlings from Euphorbia canariensis and Euphorbia lambii weregrown in the dark at 25 °C. Protein and triglyceride contentas well as levels of sugars and amino acids in the endospermwere determined during endosperm depletion. In the endospermof Euphorbia canariensis, relatively low levels of amino acids(up to 1 µmol.endosperm^–1) were found of which glutamine/glutamateaccounted for 40% at the stage of radicle emergence. High levelsof amino acids (up to 4 µmol.endosperm^–1) comparedwith sugars (up to 2 µmol sucrose.endosperm^–1) weredetected in the endosperm of Euphorbia lambii. Arginine wasthe main component (28 µmol%) of the amino acids in thistissue. In both species amino acid composition changed graduallyduring endosperm depletion. Cotyledons retained their ability to absorb a variety of watersoluble substrates after removal of the endosperm. ¹⁴C from[U-¹⁴C]sucrose was effectively incorporated into the triterpenesof the laticifers and to a lesser extent into the sterols ofthe seedling. The highest incorporation values were found inyoung seedlings about 2 d after the emergence of the radicle.Seedlings of this age also showed high incorporation rates of¹⁴C from labelled alanine, serine, threonine, valine, leucineand isoleucine into both triterpenols and sterols, but no generalconclusions about metabolic channelling in lipid synthesis couldbe made. Endosperm, Euphorbia canariensis L. Euphorbia lambii Svent., sterols, triterpenols, amino acids, laticifer, biosynthesis     

Activities of Transaminases, Amylases and Proteases during Endosperm Degradation in Normal and Opaque-2 Zea mays L. cv. Maya

Transaminase, amylase and protease activities were comparedin seedlings of normal and Opaque-2 (o2) maize. Transaminaseactivity, greater in normal maize, was highest in the scutellumfrom which it decreased rapidly in activity from day 2 afterimbibition; only low activity was observed in endosperm andaxis tissue. Amylolytic activity, optimal around pH 5, was greater in normalmaize at all stages of endosperm degradation. Activity whichwas low on day 2, rose to a peak on day 6 and declined afterwards.The level of free sugars in the endosperm of normal was higherthan in o2 maize, and in both varieties was highly correlatedwith amylolysis. Protease activity, optimal at pH 3.6, was also greater in normalendosperms and increased up to day 6 and activity was maintainedat this level until around day 14. Although the activity ofall three enzyme systems examined was greater in normal maizethere were no apparent differences in the overall growth ofnormal and o2 seedlings during this period. Zea mays L, maize, corn, endosperm, enzyme activity, transaminase, amylase, protease     

An Ultrastructural Investigation of Protein and Lipid Reserves in the Endosperm of Pinus pinea L.

Proteins and lipids are the two main storage substances in theendosperm of Pinus pinea L. In imbibed seeds, lipid and proteinbodies almost completely fill the cell volume and only a fewpoorly structured organelles can be detected. During germinationthe storage substances are reabsorbed whilst plastids, roughendoplasmic reticulum, ribosomes and polysomes, microbodies(glyoxysomes, most likely) become evident. Starch is also formed.When the cotyledons emerge completely from the endosperm envelopethe latter shows highly vacuolate cells but still rich in cytoplasmicorganelles, lipids, protein bodies and starch grains. Different patterns of protein body degradation are discussed. Pinus pinea, endosperm, ultrastructure, protein, lipid, stored reserves     

Effects of Light on the Enzymic Composition of Aegilops triaristata Seedlings

Electrophoretic patterns of enzymes, esterases, phosphatasesand peroxidases in hexaploid seedlings of Acgilops triaristatawere examined by horizontal starch gel electrophoresis. Electropherogramswere evaluated by gel densitometer traces. Comparisons weremade between organs of A. triaristata seedlings developed inlight and darkness. Each organ presented a characteristic enzymicpattern, while quantitative and qualitative differences wereobserved between organs developed in light and darkness. Thesame differences were also observed by an enzyme assay. Possiblecauses of these differences in enzyme activities, especiallyin coleoptiles, are discussed.     

Influence of leaf age, light, dark, and iron deficiency on polyribosome levels in maize leaves

The relations between leaf age and polyribosome levels werestudied with dark-and light-grown maize (Zea mays L.) seedlings.In general, polyribosome levels decline with the period of growthin darkness. Light induces an increase in the polyribosome levelin dark-grown seedlings. The response can be detected after30 min exposure to light. Seven or eight-day-old dark-growncorn seedlings, used in the present study, have high levelsof polyribosomes when greened in the light. This is indicativeof healthy seedlings, competent in protein synthesis. The polyribosomelevels in iron deficient maize plants were significantly differentfrom plants grown under complete nutrient solution, while thereis no significant difference among plants suffering differentdegrees of iron deficiency. (Received November 18, 1977; )     

Effects of light on terpene hydrocarbon synthesis in Pinus pinaster

The biosynthesis of terpene hydrocarbons has been investigated in maritime pine (Pinus pinaster Ait.) seedling primary leaves under light and darkness and with different precursors. Impossible in darkness, the synthesis of monoterpenes (mainly α- and β-pinene) is strongly activated by light. Only ¹⁴C-carbonate and ¹⁴C-acetate can be incorporated into monoterpenes. Activation by light is comparatively much more effective for seedling leaves previously cultivated under short days than in leaves from seedlings given long days. The spectral bands which are efficient for the synthesis of monoterpenes are located around 480 and 685 nm with ¹⁴C-carbonate and 480 and 630 nm with l-¹⁴C-acetate. Furthermore, this light activation does not occur if leaf pieces instead of whole leaves are used for the incorporation experiments. When 2-¹⁴C-mevalonic acid and 1-¹⁴C-isopentenyl pyrosphosphate are applied as precursors, no radioactivity is recorded in monoterpene hydrocarbons even after light exposures. In contrast, sesquiterpene hydrocarbons (caryophyllene and humulene) are easily synthesized under light or darkness in intact or fragmented leaves from the different precursors of photosynthetic or exogenous origin. From these results the compartmentalization in the synthesis of C₁₀ and C₁₅ hydrocarbons appears clear. There is a metabolic cooperation between the photosynthetic tissues and the specific site of elaboration of C₁₀ hydrocarbons, which site is located in the parts where the epithelial cells of resin ducts are functional. The synthesis of sesquiterpene hydrocarbons takes place in the whole leaf without activation by light.     

Intravacuolar Spherical Bodies in Polygonum cuspidatum

The vacuoles in the epidermal cells of light-grown seedlingsof Polygonum cuspidatum were found to contain intensely pigmentedspherical bodies (anthocyanoplasts). Dark-grown seedlings containedsimilar spherical bodies that were unpigmented. The unpigmentedspherical bodies accumulated anthocyanin and turned into anthocyanoplastswhen dark-grown seedlings were irradiated. The unpigmented sphericalbodies of dark-grown seedlings were heavily stained upon treatmentof seedlings with neutral red. The absorption spectra of sphericalbodies and vacuoles showed that the contents of the sphericalbody were different from those of the vacuole. The sphericalbody was stable in darkness or at low temperature but was unstableat 25°C in the light. There was no correlation between theamount of anthocyanin and the percentage of cells that containedspherical bodies, suggesting that, in P. cuspidatum, the sphericalbody is not the main site of anthocyanin synthesis. ²Present address: Department of Applied Biology, Faculty ofTextile Science and Technology, Shinshu University, Ueda, 386Japan     

Functional development of photosystems I and II in dark-grown pine seedlings

Green plastids prepared from seedlings of Pinus silvestris harvestedafter three weeks of growth in the dark, without exposure tolight, catalyzed photoreductions of methyl viologen and nicotinamide-adeninedinucleotide phosphate, and cyclic photophosphory-lation withN-methylphenazonium methosulfate, but could not catalyze thephotoreduction of 2,4-dichlorophenol indophenol in the absenceand presence of diphenylcarbazide. In dark-grown seedlings ofPinus silvestris, functional photosystem I developed with noexposure to light, but no photosystem II activity was abserved. (Received August 22, 1973; )     

The role of carbohydrates in seed germination and seedling establishment of Himatanthus sucuuba, an Amazonian tree with populations adapted to flooded and non-flooded conditions

Background and Aims

In the Amazonian floodplains plants withstand annual periods of flooding which can last 7 months. Under these conditions seedlings remain submerged in the dark for long periods since light penetration in the water is limited. Himatanthus sucuuba is a tree species found in the ‘várzea’ (VZ) floodplains and adjacent non-flooded ‘terra-firme’ (TF) forests. Biochemical traits which enhance flood tolerance and colonization success of H. sucuuba in periodically flooded environments were investigated.

Methods

Storage carbohydrates of seeds of VZ and TF populations were extracted and analysed by HPAEC/PAD. Starch was analysed by enzyme (glucoamylase) degradation followed by quantification of glucose oxidase. Carbohydrate composition of roots of VZ and TF seedlings was studied after experimental exposure to a 15-d period of submersion in light versus darkness.

Key Results

The endosperm contains a large proportion of the seed reserves, raffinose being the main non-structural carbohydrate. Around 93 % of the cell wall storage polysaccharides (percentage dry weight basis) in the endosperm of VZ seeds was composed of mannose, while soluble sugars accounted for 2·5%. In contrast, 74 % of the endosperm in TF seeds was composed of galactomannans, while 22 % of the endosperm was soluble sugars. This suggested a larger carbohydrate allocation to germination in TF populations whereas VZ populations allocate comparatively more to carbohydrates mobilized during seedling development. The concentration of root non-structural carbohydrates in non-flooded seedlings strongly decreased after a 15-d period of darkness, whereas flooded seedlings were less affected. These effects were more pronounced in TF seedlings, which showed significantly lower root non-structural carbohydrate concentrations.

Conclusions

There seem to be metabolic adjustments in VZ but not TF seedlings that lead to adaptation to the combined stresses of darkness and flooding. This seems to be important for the survival of the species in these contrasting environments, leading these populations to different directions during evolution.     

Alteration of Soybean Seedling Development in Darkness and Light by the Stay-green Mutation cytG and Gd1d2

The stay-green mutations cytG and Gd₁d₂ prevent the normal yellowingduring senescence of soybean (Glycine max) leaves and cotyledons.Because light plays such an important role in regulating morphogenesisand it promotes the formation of chlorophyll (Chl), we determinedthe effect of cytG and Gd₁d₂ (in a cv. Clark background) onthe development and some light responses of seedlings. AlthoughcytG and Gd₁d₂ seeds, particularly the cotyledons, are greenwhen mature, 44 and 71 % respectively of this Chl broke downwhen the seeds were germinated in darkness. Chlorophyllidesand phaeophytins were not present in the seeds in significantamounts. cytG and Gd₁d₂ as well as wild type (cv. Clark) seedlingsdeveloped a full etiolation syndrome (morphology and lack ofChl) in darkness. Light induced rapid Chl accumulation in thedark-grown seedlings with no apparent difference among the threeisolines. A short (8 h) exposure to light induced some Chl inthe cotyledons of dark-grown plants, and 22 h of light producedfour times more. Following return to darkness, the 8-h groupshowed very little breakdown over the next 12 d. After the 22-hgroup was returned to darkness, the wild-type lost Chl steadily,but Gd₁d₂ and eventually also cytG inhibited this breakdown.In the 22-h group, the Chl a/b ratio decreased in wild typeand cytG indicating preferential breakdown of Chl a relativeto Chl b; however, Gd₁d₂ prevented this change. cytG and Gd₁d₂seem to act preferentially on Chl breakdown rather than synthesis.Copyright1995, 1999 Academic Press Glycine max, soybean, chlorophyll, chlorophyll a/b ratio, cotyledons, etiolation, cytG, Gd₁d₂, mutations, senescence     

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)     

Ricerche Comparate Sulla Morfologia e Sulla Fisiologia di Larix e di Picea

Abstract

Comparative researches on morphology and physiology of PICEA and LARIX. The chlorophyll content of seeds and seedlings during germinations in darkness. — Very different are the chlorophyll contents of the seeds and the seedlings of Picea excelsa and Larix decidua grown in darkness.

In Picea chlorophyll is abundantly synthetized in cotyledons in the passage from seed to seedling stages. In Larix however this synthesis is very poor. These differences are more evident after the outgrowth of cotyledons from the primary endosperm and its exhaustion.

If seedlings of both species are exposed to 3.000 lux of light intensity for 24 hours, after development in darkness, one can observe much stronger chlorophyll synthesis in Larix cotyledons than icea.

These figures quanti atively express the different light-dipendence of chlorophyll synthesis in these two plants and offer a more adherent interpretation of the different ecological behaviours that are caracteristic of these two plants.     

Metabolism and Translocation of Exogenous Zeatin Riboside in Germinating Seeds and Seedlings of Zea mays

High specific activity [³H]-zeatin riboside (ZR) was suppliedto germinating seed and developing seedlings of Zea mays tostudy its metabolism and translocation The major metabolitesof ZR in endosperm, embryo, and first leaves were adenosine,adenine, and adenine nucleotide When ZR was supplied to theradicle tip a significant proportion of the radioactivity extractedfrom the radicle was identified as zeatin-9-glucoside (Z9G).However, some ZR was also transported to the shoot and vestigialembryo During the initial stage of germination, movement ofzeatin riboside from the embryo to the endosperm was pronouncedbut little movement occurred in the reverse direction Key words: Zea mays cytokinin, zeatin riboside, metabolism, translocation     

An Endogenous 24-hour Rhythm in the Growth Rate of the Avena Coleoptile

The rates of growth of coleoptiles of intact Avena seedlingswere studied by means of time-lapse photography, using infra-redradiation. When the seedlings are germinated in red light and subsequentlytransferred to darkness, a growth rhythm is established in whichthe first peak in the growth-rate curve occurs about 16–17hours after the transfer, and the second peak 24 hours later.When the transfer is made sufficiently early, three peaks mayoccur before growth ceases. The occurrence of the peaks andthe emergence of the primary leaf are independent of one another. Alteration of the point in the life-history at which the seedlingsare transferred from light to darkness changes the times ofoccurrence of the peaks, but does not affect the period of therhythm. The incidence of the rhythm shows no correlation withtime of day; therefore the rhythm is not due to diurnal changesin external conditions. Interruption of the dark period by several hours' exposure tored light causes the suppression of a previously induced rhythmand the establishment of a new one which commences at the timethe seedlings are restored to darkness. When they are grownunder continuous red light no rhythm is induced. Within the range 16 to 28 C., temperature has little or noeffect on the period of the rhythm. When seedlings of Triticum are grown under the same conditionsas those which induce a rhythm in Avena, no rhythmical variationin the growth rate can be detected.     

Formation of Chlorophyll-Protein Complexes in Greening Cucumber Cotyledons in Light and then in Darkness

The changes in chlorophyll-protein complexes (CPs) in cucumbercotyledons during illumination and subsequent dark incubationwere studied by SDS-polyacrylamide gel electrophoresis. Whenetiolated cucumber seedlings were illuminated, chlorophyll wassynthesized and CPs were formed. In the early phase of greening(6 h of illumination), light-harvesting chlorophyll a/b-proteincomplex (LHCP) was the main GP. As the greening proceeded, P700chlorophyll a-protein complex (CP1) accumulated. When 6-h illuminatedseedlings were transferred to darkness, CP1 accumulated concomitantlywith a decrease in LHCP without new chlorophyll synthesis. Thechanges in the amounts of CPs in the dark became smaller withthe progress of greening and were not observed after 72 h ofillumination. These changes were confirmed by examining thechlorophyll/P700 ratio and the low temperature absorption spectrumof cotyledons. These results suggest that in the early phaseof greening, CPs were unstable and their chlorophyll moleculeseasily exchanged with those of other kinds of CPs. (Received October 14, 1982; Accepted December 1, 1982)     

Importance of Endosperm for Nutrition of Fraxinus pennsylvanica Seedlings

Contact between endosperm and cotyledons of germinating Fraxinuspennsylvanica Marsh. seedlings was not essential for continuationof seedling growth or adaptation of cotyledons for photosynthesis.However, when cotyledons were in contact with endosperm, thecotyledons had faster rates of elongation and dry weight increase,slower depletion of reserves, and higher chlorophyll contents.Photosynthetic contributions by cotyledons may be enhanced ifenviron mental conditions support rapid emergence of cotyledonsfrom surrounding seed structures.     

NO2 Suppression of Light-Induced Nitrate Reductase in Squash Cotyledons

NADH-nitrate reductase (NR) (EC 1.6.6.1 [EC] ) activity in the cotyledonsof squash (Cucurbita maxima Duch.) seedlings showed daily variationwhen the seedlings were subjected to an alternating light-darkcycle. When the seedlings were transferred into continuous darkness,NR activity rose at first and then decreased continuously. Irradiationafter continuous darkness induced a rapid increase in NR activity;this light induction of NR activity was inhibited completelyby fumigation with 4 ppm nitrogen dioxide (NO₂). This inhibitoryeffect of NO₂ was prominent even at 1 ppm and became more pronouncedas the concentration of NO₂ increased. NO₂ fumigation did notremarkably affect the content of reductant (NADH) in the cotyledons.The results of immunoblotting using anti-NR serum indicatedthat irradiation induced the increase in the NR-polypeptidecontent and NO₂ fumigation inhibited the increase, suggestingthat NO₂ put an inhibitory effect on the synthesis of NR inducedby irradiation. ⁴ Present address: College of Environmental Health, Azabu University,Fuchinobe, Sagamihara, Kanagawa 229, Japan ⁵ Present address: Faculty of Home Economics, Otuma Women'sUniversity, Sanban-cho, Chiyoda, Tokyo 102, Japan (Received October 21, 1987; Accepted January 13, 1988)