Analysis of Lipids of Citrullus lanatus (cv. Sugar baby) During Seed Germination and Seedling Growth

Changes in the dry weight (dry wt.), total and neutral lipids,and fatty acid composition were determined in the cotyledonsand axis of Citrullus lanatus cv. Sugar baby seedlings duringtheir first 12 d growth in the dark, at 25 ? 1 ?C. The major stored reserves were mobilized between days 3 and8. The lipid concentration after day 4 decreased rapidly inthe cotyledons. On the first day the lipid concentration inthe axis was higher than in the cotyledons but decreased rapidlyand from day 5 up to the end of the experiments it remainedat very low values. In the cotyledons, the change in the fattyacid composition was relatively small compared to the significantchange observed in the axis. The neutral lipids of the cotyledonsdecreased sharply between days 2 and 6 while their fatty acidcomposition suffered no significant change. The axis, comparedto the cotyledons, contained a small but concentrated amountof neutral lipids, which decreased up to day 6. Thereafter,an increase was observed. The fatty acid composition of theaxis neutral lipids changed significantly, linoleic and oleicacid decreased while palmitic and linolenic acid increased. Key words: Citrullus lanatus, seed germination, seedling growth, lipids, fatty acids     

Mobilisation of the major stored reserves in the embryo of fenugreek (Trigonella foenum-graecum L., Leguminosae), and correlated enzyme activities

Changes in total nitrogen, soluble amino nitrogen, lipid and phytate contents, and in the activities of proteinase (pH 7.0), isocitrate lyase and phytase were followed in the endosperm, cotyledons, and axis during germination of fenugreek seeds and subsequent growth of the seedlings. The endosperm is comprised largely of cell-wall galactomannans: the majority of the seed total nitrogen, lipid and phytate (5%, 8%, 0.44% of seed dry weight respectively) is localised within the cotyledons as stored reserves. Germination is completed after 10–14 h from the start of imbibition, but the major reserves are not mobilised during the first 24 h. Then the total nitrogen content of the cotyledons starts to decrease and that of the axis increases; there is a concomitant accumulation of soluble amino nitrogen in both cotyledons and axis. An increase in proteinase activity in the cotyledons correlates well with the depletion of total nitrogen therein. Depletion of lipid and phytate reserves in the different seed tissues constitutes a late event, occurring after 50 h from the start of imbibition, and is coincident with the final disintegration of the endosperm tissue. The depletion of phytate and stored lipids is accompanied by an increase in phytase and isocitrate lyase activity. It appears that the products of lipid hydrolysis are converted by gluconeogenesis to serve as the major source of sugars for the growing axis after the endosperm galactomannan has been completely mobilised.     

Protein Synthesis During Rehydration, Germination and Seedling Growth of Naturally and Precociously Matured Soybean Seeds (Glycine max)

Soybean seeds [Glycine max (L.) Merr.] synthesize de novo andaccumulate several non-storage, soluble polypeptides duringnatural and precocious seed maturation. These polypeptides havepreviously been coined ‘maturation polypeptides’.The objective of this study was to determine the fate of maturationpolypeptides in naturally and precociously matured soybean seedsduring rehydration, germination, and seedling growth. Developingsoybean seeds harvested 35 d after flowering (mid-development)were precociously matured through controlled dehydration, whereasnaturally matured soybean seeds were harvested directly fromthe plant. Seeds were rehydrated with water for various timesbetween 5 and 120 h. Total soluble proteins and proteins radio-labelledin vivo were extracted from the cotyledons and embryonic axesof precociously and naturally matured and rehydrated seed tissuesand analyzed by one-dimensional PAGE and fluorography. The resultsindicated that three of the maturation polypeptides (21, 31and 128 kDa) that had accumulated in the maturing seeds (maturationpolypeptides) continued to be synthesized during early stagesof seed rehydration and germination (5–30 h after imbibition).However, the progression from seed germination into seedlinggrowth (between 30 and 72 h after imbibition) was marked bythe cessation of synthesis of the maturation polypeptides followedby the hydrolysis of storage polypeptides that had been synthesizedand accumulated during seed development. This implied a drasticredirection in seed metabolism for the precociously maturedseeds as these seeds, if not matured early, would have continuedto synthesize storage protein reserves. Glycine max (L.) Merr, soybean, cotyledons, maturation, germination/seedling growth     

Utilization of Seed Reserves and Currently Produced Photosynthates by Embryonic Tissues of Pine Seedlings

The importance of seed reserves for growth of Pinus resinosaAit. during and shortly after seed germination was studied undercontrolled conditions. Tissues in the resting embryo were notcompletely differentiated. Many small, presumably reserve particleswere present in the embryo in addition to reserves in the megagametophyte.During seed germination, procambia in the embryo first differentiatedprotophloem 2 days after seeds were sown. The radicle beganto emerge from the seed coat at 5 days, at which time initialxylem formation was observed. Also, at approximately the sametime, primordia of primary needles were forming in the peripheralzone of the apex. Elements of the photosynthetic apparatus,including stomata and mesophyll with chloroplasts, were differentiatedfirst in the hypocotyl and then in cotyledons between 5 and8 days after seeds were sown. Photosynthetic rates of youngseedlings were correlated with rates of cotyledon expansion.During early developmental stages, reserve particles in megagametophytecells and embryo cells gradually disappeared. Surgical removalof megagametophytes at various stages of seed germination resultedin subsequent growth inhibition of the hypocotyl-radicle axis,with early removal of cotyledons suppressing most growth. Growthof primary needles appeared to be influenced indirectly by megagametophytereserves, probably by changes in amount of photosynthetic tissue.The embryo alone possessed capacity to differentiate such tissuesas primary needle primordia, stomata, and primary and secondaryvascular systems. Megagametophyte reserves appeared to contributeto growth of embryonic tissues only after the embryo itselfinitiated growth. Both current photosynthesis of seedlings andseed reserves contributed importantly to seedling development.     

Protein Bodies of Germinating Seeds of Vicia faba: CHANGES IN FINE STRUCTURE AND BIOCHEMISTRY

Changes in fine structure and starch, total nitrogen and solublesugar contents were followed during the first 3 weeks of germinationin Vicia faba cotyledons. Following hydration the reserves were mobilized and loss ofprotein from the cotyledons began after 4 days; concomitantfine structural changes included the swelling and coalescenceof protein bodies, the disappearance of their contents, andthe differentiation of the provascular tissue in the cotyledonwithin which ‘transfer cells’ developed. There wassome development of rough endoplasmic reticulum during the earlypart of germination. A pattern of protein-body degradation appeared in the cotyledonsduring germination, those cells nearest to the vascular bundlesand to the epidermis being the first to lose their reserves.After 3 weeks' growth the parenchyma cells of the cotyledonwere very vacuolate and typical of senescent tissue, while thevascular bundle cells still retained their contents and remainedactive-looking.     

Changes in Cell Fine Structure in the Cotyledons of Phaseolus vulgaris L. during Germination

When germination begins, the storage cells of Phaseolus vulgariscotyledons are packed with starch grains and protein bodies.Digestion of these reserves starts in cells furthest away fromthe vascular bundles and is practically completed in eight daysat 25° C. After the reserves are hydrolysed, the storagecells die. The changes in fine structure during the processof digestion and protoplasmic breakdown are described. Vascularbundle and epidermal cells survive till the cotyledons absciss,but in these tissues also profound changes occur in cellularorganization. The observations on fine structure are discussedwith reference to the metabolic activities of the cotyledons.     

Growth Analysis of Soybean Seedlings During the Lifespan of the Cotyledons

Patterns of seedling growth of Glycine max in light and darknesswere compared during the period from germination to cotyledonabscission. Fitted growth curves and the derived functions,relative growth rate, unit leaf rate, leaf area ratio and specificleaf area, were used to assess the relative importance in seedlinggrowth of cotyledon storage reserves, cotyledon photosynthesisand leaf photosynthesis. The cotyledons are of an intermediatetype with a predominant storage and a minimal photosyntheticfunction. Cotyledon reserves support seedling growth until theprimary leaves expand, after which growth depends on leaf photosynthesis. Glycine max (L.) Merr., soybean, cotyledons, growth analysis, seedling development     

The Role of Maturation Drying in the Transition from Seed Development to Germination: IV. PROTEIN SYNTHESIS AND ENZYME ACTIVITY CHANGES WITHIN THE COTYLEDONS OF RICINUS COMMUNIS L. SEEDS

Drying of immature seeds of Ricinus communis L. cv. Hale (castorbean) during the desiccation-tolerant phase of development causesthem to germinate upon subsequent rehydration. This desiccation-inducedswitch from development to germination is also mirrored by achange in the pattern of soluble and insoluble protein synthesiswithin the cotyledons of the castor bean. Following rehydrationof seeds prematurely dried at 40 d after pollination (DAP),cotyledonary proteins characteristic of development (e.g. storageproteins) are no longer synthesized; hydrolytic processes resultingin their degradation commence (after 12 h) in a manner similarto that observed following imbibition of the mature seed. Apattern of protein synthesis recognizable as germination/growth-associatedoccurs; premature drying has elicited a redirection in metabolismfrom a developmental to a germinative mode. Desiccation is alsorequired for the induction (within cotyledons of 35 DAP seeds)of enzymes involved in protein reserve breakdown (leucyl ß-naphthylamidase;LeuNAase) and lipid utilization (isocitrate lyase; ICL), anevent intimately associated with the post-germinative (growth)phase of seedling development. Thus, at a desiccation-tolerantstage of development, premature drying results in the suppressionof the developmental metabolic programme and a permanent switching-onof the germination/growth metabolic programme. Key words: Desiccation, metabolism, seed development, seed germination, castor bean, cotyledons     

BIOCHEMICAL COMPOSITION AND METABOLIC ACTIVITY OF SCRIPPSIELLA TROCHOIDEA (DINOPHYCEAE) RESTING CYSTS1

The composition and metabolic activity of cysts of the marine dinoflagellate Scrippsiella trochoidea (Stein) Loeblich were examined during dormancy, quiescence, and germination. On a per cell basis, newly formed cysts contained an order of magnitude more carbohydrate but significantly less protein and chlorophyll a than did exponentially growing vegetative cells. Loss of lipid and carbohydrate from cysts during the initial dormancy period reflected a respiration rate estimated to be 10% of the respiratory activity in vegetative cells. Among older, quiescent cysts the calculated respiration rate decreased further to approximately 1.5% of the vegetative rate and appeared to proceed largely at the expense of carbohydrate reserves. These estimated rates of respiration were in good agreement with direct measurements of cyst oxygen consumption. The transfer of quiescent cysts to conditions permissive for germination resulted in a rapid increase in respiration rate, as evidenced by carbohydrate loss and O₂ consumption. The increased respiratory activity was followed by an increase in protein content and, later, by an increase in chlorophyll a content and photosynthetic capacity. Just prior to germination the P/R ratio became greater than 1, and the estimated chlorophyll-specific photosynthetic activity reached 75% of the rate in vegetative cells. Complete restoration of photosynthetic and respiratory capacity apparently was not achieved until after excystment. These data confirm the common assumption that dinoflagellate cysts represent true “resting” cells, containing extensive energy reserves and displaying greatly reduced metabolic activity.     

Distribution and changes of reserve materials in cotyledon cells of Panax ginseng related to direct somatic embryogenesis and germination

Cotyledon explants from zygotic embryos of Panax ginseng produced somatic embryos on Murashige and Skoog basal medium without growth regulators. Somatic embryos developed directly from epidermal cells at the cotyledon base. Somatic embryos were always formed from the side of the cotyledon opposite to the one attached to the medium surface regardless of cotyledon orientation. The frequency of somatic embryo formation from the abaxial epidermis (66%) was much higher than that from the adaxial epidermis (12%). Differences in embryogenic response were likely related to cell structure. Abaxial epidermal cells were filled with reserve materials (lipid bodies), while adaxial epidermal cells were devoid of any prominent reserves. During germination, the reserve materials in the cells of the cotyledons disappeared rapidly. At the same time, the competency of somatic embryo formation from cotyledon explants declined rapidly to zero. Upon culture of the cotyledon explants (for somatic embryo induction), lipid bodies slowly disappeared, but starch grains accumulated prominently. Reserve materials disappeared after commencement of embryogenic cell division. During germination, lipid bodies rapidly disappeared, and chloroplasts developed instead of starch grains. Received: 29 January 1997 / Revised version received: 16 April 1997 / Accepted: 9 May 1997     

Distribution and utilization of chlorogenic acid in Coffea seedlings

Ripe coffee seeds (Coffea arabica L.) contain large quantitiesof the purine alkaloid caffeine and the depside chlorogenicacid (5-O-caffeoyl-quinic acid). Directly after germination,both compounds were recovered almost exclusively in the cotyledonsand surrounding endosperm and hardly at all in the hypocotyland root of coffee seedlings. During the first 10 weeks of development,the cotyledons invaded the endosperm and expanded. The caffeinecontent in the developing cotyledons changed little, but thechlorogenic acid content dropped to one-third of the originallevel. The loss of chlorogenic acid was not recovered in theother organs of the seedling. The drop in chlorogenic acid contentcoincided with an increase in the amount of cell wall-boundphenolic polymers in the developing cotyledons, which couldbe extracted after thioglycolic acid derivatization. In thedeveloping cotyledons, phenylalanine ammonia lyase (PAL) activitywas hardly detectable. These results suggest that the chlorogenicacid stored in coffee seeds is used for the deposition of phenolicpolymers, presumably lignin, in cotyledonary cell walls duringexpansion. The situation in cotyledons was found to be in markedcontrast to that in foliage leaflets, in which PAL activitywas 900-fold higher than in cotyledons. In the leaflets, bothchlorogenic acid and caffeine accumulated continuously duringleaf expansion. Key words: Coffea arabica, seedling, chlorogenic acid, caffeine     

Nuclear Proteins During the Onset of Cell Proliferation in Pea Root Meristems

The DNA: proteins ratio in nuclei of root meristems of pea (Pisumsativum L. cv. Lincoln) changed considerably during germinationas cells moved from a quiescent to an actively proliferatingstate with a higher protein content in nuclei of the latter.Electrophoretic patterns of nuclear proteins extracted at differenttimes of germination were used to examine qualitative changes.The various patterns presented a substantial similarity butthere were some proteins whose content increased or decreasedand others which disappeared or appeared during germination.The bulk of these variations occurred between 24 and 48 h ofgermination, suggesting that they might be correlated to thetransition from quiescence to the proliferating state. The patternof nuclear proteins obtained from adult differentiated roottissue was also examined. We tried to purify five differentnuclear protein components from intact nuclei by a multi-stepextraction procedure using a series of different buffers toascertain the nature of proteins presenting major interestingvariations. Most of these proteins purified with the nuclearsap or ribosomal components. Key words: Cell proliferation, electrophoresis, Pisum sativum L, root meristems     

Compositional changes in germinating spores ofAdiantum capillus-veneris L.

Spores ofAdiantum capillus-veneris L. incubated at 25 C for 3 days in the dark were irradiated with continuous red light to induce spore germination and cell growth during following 7 days. A portion of spores were cultured for 8 days in the dark as non-irradiated control. Rhizoidal and protonemal cells were observed at 3 days after transferring spores to the irradiation conditions. During 10 days of the experimental period, changes in the contents of following cell constituents were investigated: total lipid, total soluble sugar, reducing sugar, insoluble glucan, organic acid, protein, soluble α-amino N, and major free amino acids. A large part of nutrient reserves of spores was found to be lipid, whose content decreased markedly as spores germinated. Soluble and insoluble carbohydrates also provided carbon and energy sources during imbibition and germination. Two main reserve proteins were detected by SDS-polyacrylamide gel electrophoresis. These proteins disappeared mostly during germination. Major free amino acids could be assorted into three groups by their patterns of fluctuation during the germination.     

Changes in Seed Constituents During Germination and Seedling Growth of Precociously Matured Soybean Seeds(Glycine max)

During 7 d of precocious maturation of soybean seed (Glycinemax), the starch content declined and soluble sugar levels increasedin patterns similar to natural seed dehydration and maturation.Total seed protein content and total seed dry weight increasedwhereas oil content remained relatively unchanged. Overall,the proportions of the constituents in precociously maturedseeds were comparable to naturally mature seeds. Precociouslymatured soybean seeds showed much the same germination and seedlinggrowth frequency patterns as naturally matured seeds. Duringgermination and seedling growth of precociously matured seeds,starch, soluble sugar, protein and oil levels followed patternssimilar to naturally mature, germinating seeds and seedlings.Therefore, precocious maturation may be used as a model systemto investigate the control of the physiological and biochemicalevents occurring during seed maturation which lead to germinationand subsequently, seedling growth. Glycine max (L.) Merr., soybean, cotyledons, maturation, germination/seedling growth     

Changes in Abscisic Acid Content in Axis and Cotyledons of Developing Phaseolus vulgaris Embryos and their Physiological Consequences

Prevost, I. and Le Page–Degivry, M. Th. 1985. Changesin absicisic acid content in axis and cotyledons of developingPhaseolus vulgaris embryos and their physiological consequences.—J.exp. Bot. 36: 1900–1905.Changes in abscisic acid (ABA)content with time were measured in embryonic axes and in cotyledonsof Phaseolus vulgaris embryos using a radio–immunoassay.During embryogenesis, a similar pattern was observed in bothtissues: ABA increased to a maximum 29 d after an thesis, followedby a decrease as the seed matured. The level of ABA in the cotyledonswas always much higher than that in the axes. In in vitro cultures,the duration of the lag phase before germination of isolatedembryonic axes increased with ABA content. The presence of cotyledonsalways lengthened the lag phase; longer lag phases were associatedwith greater concentrations of ABA in the cotyledons. Moreoverthe presence of cotyledons stimulated the growth of seedlings. Key words: ABA distribution, embryo maturation, axis and embryo germinability     

Changes in the Content of Starch and Activities of some Enzymes of Carbohydrate Metabolism in Cotyledons of Germinating Seeds of Voandzeia subterranea

During the germination of the seeds of Voandzeia subterraneaL. Thouars, the content of starch in the cotyledons fell progressively.There was a substantial increase in amylase activity duringthe first 4 d. The activity of starch phosphorylase increasedafter 6 d when there was a rapid decline in amylase activity.The activities of hexokinase, glucose-6-phosphate dehydrogenase,and 6-phosphogluconate dehydrogenase increased, suggesting thepresence of an active phosphogluconate pathway in the cotyledons.     

Transport and Metabolism of Dihydrozeatin Riboside in Germinating Lupin Seeds

[³H]-dihydrozeatin riboside was applied selectively to the embryonicaxes or to the cotyledons of germinating lupin (Lupinus luteusL. cv. Weiko III) seeds 6 h following the start of imbibition.There was little transport of dihydrozeatin riboside from embryoto cotyledons up to 6 h after the application, but a substantialamount of radioactivity had moved into the cotyledons at theend of the 10 h incubation period. However, there was no detectablemovement of [³H]-dihydrozeatin riboside from the cotyledonsto the embryonic axis. This indicated a highly polarized movementof cytokinins during the early stages of seed germination. Exogenouslyapplied [³H]-dihydrozeatin riboside was found to be very stable,both when applied to the embryonic axes and cotyledons of intactseed, or following excision, and there was little metabolismwith only small amounts of radioactivity found associated withdegradative metabolites. The embryonic axis of this specieshas recently been found to synthesize cytokinins within 12 hfrom the start of imbibition, and the results of this studyindicate that the embryo-derived cytokinin is probably transportedto the cotyledons where it accumulates and subsequently participatesin the control of cotyledon function. Key words: Lupinus luteus, cytokinin transport and metabolism, dihydrozeatin riboside, seed germination     

The inhibited seed germination by ABA and MeJA is associated with the disturbance of reserve utilizations in Astragalus membranaceus

Astragalus membranaceus is a major traditional Chinese medicinal plant. Here, we investigated the mobilizations of seed reserves during its germination and post-germination growth, as well as the effects of exogenous abscisic acid (ABA) and methyl jasmonate (MeJA). It was found that both starch and protein were rapidly mobilized during the seed germination. However, lipid was mostly utilized during the post-germination. Exogenous ABA and MeJA treatments significantly inhibited the germination and post-germination growth. Meanwhile, the treatments decreased the weight of mobilized seed reserves and seed reserves utilization efficiency, retarded the mobilizations of protein and lipid, and led to excessive consumption of carbon energy. Moreover, the treatments changed fatty acid compositions in cotyledons, with the decreasing of the double bond index and average carbon chain length. This study will help us to understand the inhibition mechanism of exogenous ABA and MeJA on the germination and post-germination growth of A. membranaceus.     

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     

On the Composition, Deposition and Mobilization of Proteins in the Cotyledons of Castor Bean (Ricinus communis L. cv. Hale) Seeds: Their Role as Storage Proteins

Proteins in the soluble and insoluble fractions, extracted frommature castor bean cv. Hale seed cotyledons, differ quantitativelyand qualitatively from their counterparts extracted from theendosperm. The soluble fraction contains no glycoproteins, andthe lectins RCA₁ and ricin D are absent. While the insolubleproteins are electrophoretically and immunologically similarto those in the endosperm, they do not form the 100 kD subunitdimers which characterize some of the endosperm insoluble crystalloidproteins. Rapid rates of deposition of all of the soluble andinsoluble proteins present in the mature seed cotyledons commences30–35 d after pollination (DAP) and continues until 45DAP. These proteins are mobilized rapidly beginning 1–2d after seed imbibition and this coincides with an increasein specific activity, in the cotyledons, of two aminopeptidasesand a carboxypeptidase. The soluble and insoluble proteins inthe cotyledons of the mature seed probably function as storageproteins and support the growth of the germinated seed priorto the mobilization of the major protein storage reserves ofthe endosperm. Key words: Ricinus communis, Castor bean, Hale cultivar, Cotyledon, Storage protein, Seed development, Seed germination