Level of Abscisic Acid in Integuments, Nucellus, Endosperm, and Embryo of Peach Seeds (Prunus persica L. cv Springcrest) during Development

Free abscisic acid (ABA) in integuments, nucellus, endosperm, and embryo was determined throughout seed development of peach (Prunus persica L. cv Springcrest). Quantification of ABA was performed using combined high performance liquid chromatography-radioimmunoassay based on a monoclonal antibody raised against free (S)-ABA. In the integuments and endosperm, ABA concentration remained constant during the first 100 days after anthesis and rose in the following days when fresh weight was rapidly decreasing. In the nucellus, the ABA concentration variation pattern paralleled that of tissue growth. ABA concentration in the embryo increased constantly with the growth of the tissues to reach a maximum at the last growth stage. The role of ABA in peach seeds is discussed in relation to the development of the different seed tissues.     

On the Structure of Lettuce (Lactuca sativa L.) Endosperm during Germination

Endosperm cells of lettuce (Lactuca sativa L.) are characterizedby thick cell walls and dense cytoplasm which contains numerousprotein bodies. Other organelles such as nucleus, mitochondria,plastids and dictyosomes are typical of plant cells. Light andelectron microscopy reveal that before radicle emergence micropylarcells of endosperm tissue undergo drastic protoplast alterations.These alterations seem to be the only structural modificationsbefore rupturing of the tissue since the walls of the endospermcells seem to degrade only after radicle emergence. The differentialbehaviour of the micropylar area of the endosperm before radicleemergence and the observation that the micropylar cells remainmetabolically active long after radicle emergence while therest of the tissue is almost completely disintegrated, suggeststhat the endosperm cells of the micropylar area may have a roleother than being a main reserve site like the rest of the endosperm. Lactuca sativa L., endosperm structure, seed germination, lettuce     

Efficient and Stable Transformation of Lactuca sativa L. cv. Cisco (lettuce) Plastids

Transgenic plastids offer unique advantages in plant biotechnology, including high-level foreign protein expression. However, broad application of plastid genome engineering in biotechnology has been largely hampered by the lack of plastid transformation systems for major crops. Here we describe the development of a plastid transformation system for lettuce, Lactuca sativa L. cv. Cisco. The transforming DNA carries a spectinomycin-resistance gene (aadA) under the control of lettuce chloroplast regulatory expression elements, flanked by two adjacent lettuce plastid genome sequences allowing its targeted insertion between the rbcL and accD genes. On average, we obtained 1 transplastomic lettuce plant per bombardment. We show that lettuce leaf chloroplasts can express transgene-encoded GFP to ~36% of the total soluble protein. All transplastomic T0 plants were fertile and the T1 progeny uniformly showed stability of the transgene in the chloroplast genome. This system will open up new possibilities for the efficient production of edible vaccines, pharmaceuticals, and antibodies in plants.     

苏铁(Cycas revoluta Thunb.)种子的胚与胚乳解剖结构研究

对苏铁(Cycas revoluta Thunb.)种子的胚和胚乳组织进行了解剖研究。结果表明:苏铁种子为有胚乳种子,兼有胚乳和外胚乳,成熟时具直立型胚。胚乳的表层细胞含有角蜡质,胞核大,不含淀粉粒;中层细胞胞核明显;内层细胞胞核不明显,富含淀粉颗粒,淀粉粒单脐点明显。胚孔端的胚乳内陷成一凹槽,似贮藏窖。成熟的子叶胚为倒生胚胎,位于胚乳细胞解体后形成的囊腔中,子叶胚长度在胚乳中占到种子的1/3至2/3,已达到生理成熟阶段。双子叶直立,半合生。胚状体基部呈喙状突起,喙状突起下端连着一根肠叠着的丝状吸器,吸器基部连着一个小气囊。胚芽由顶端分生组织和数枚真叶组成,此时真叶已具羽状叶原基和绒毛原始体。在胚状体中发现有长管细胞及螺纹加厚的导管,在子叶中脉有数条并列的螺环纹导管。     

Studies on the Chemical Induction of a Light Requirement for Germination in Seeds of Lettuce, Lactuca sativa L., cv. 'Great Lakes'

Detailed time courses of germination were recorded for threeseed batches of lettuce, cv. ‘Great Lakes’. Thegermination of this variety is usually considered to be insensitiveto light, but considerable variability was noted between seedbatches with respect to the effect of light. Previous reportson the chemical induction of a light requirement for germinationin lettuce seeds were not substantiated for this variety. Naringeninwas found to be relatively ineffective, and although coumarin,ABA, and IAA all delayed germination with increasing concentration,this delay was not diminished by continuous light. The inhibitionsof germination by sucrose, mannitol, Carbowax, sodium chloride,potassium chloride, and potassium nitrate were also similarin light and darkness; these inhibitions appeared to relateto the osmotic pressures of the solutions. It is postulatedthat previous reports of chemical induction of a light requirementmay be the result of presenting germination figures at one pointin time. Analysis of germination by detailed time courses showedthat while prolonged light irradiation slightly acceleratedgermination, perhaps by raising seed temperature, it in no wayovercame chemical inhibition.     

The Development of Green Onion (Allium Fistulosum L. )Embryo and Endosperm

Embryo development of Zhangqiu green onion conforms to the Asterad type and goes through the following stages: proembryo, globular, ellipsoidal, laterally concave, stick-shaped, and curved and mature. The persistent synergid is present until the late globular stage of embryogenesis. Endosperm development of Zhangqiu green onion follows the nuclear pattern. Endosperm cell formation begins at both the micropylar end and the chalazai end of the embryo sac when the embryo is in the late globular stage. Due to the anticlinal wall formation, a layer of free nuclei becomes a layer of “open cells” which lack the inner periclinat wall. The open cells undergo cell division periclinally, and a layer of complete cells is cut off outside and a new layer of open cells inside. The subsequent cell divisions give rise to the endosperm cells centripetally until those from the opposite of the embryo sac meet. The first anticlinal walls arise from the cell plates without phragmoplasts between the free nuclei in interphase. The first periclinal walls are formed by normal cytokinesis. When a few layers of endosperm cells are formed at the micropylar end and the chalazal end of the embryo sac, free cells are present in the central vacuole.     

Blue and Green Light-Induced Phototropism in Arabidopsis thaliana and Lactuca sativa L. Seedlings

Exposure time-response curves for blue and green light-induced phototropic bending in hypocotyls of Arabidopsis thaliana (L.) Heynh. and Lactuca sativa L. seedlings are presented. These seedlings show significant phototropic sensitivity up to 540 to 550 nanometers. Since wave-lengths longer than 560 nanometers do not induce phototropic bending, it is suggested that the response to 510 to 550 nanometers light is mediated by the specific blue light photoreceptor of phototropism. We advise care in the use of green `safelights' for studies of phototropism.     

Degradation of the endosperm cell walls of Lactuca sativa L., cv. Grand Rapids

The timing of mobilisation of lipid, sucrose, raffinose and phytate in lettuce seeds (achenes) (cv. Grand Rapids) has been examined. These reserves (33%, 1.5%, 0.7%, 1.4% of achene dry weight, respectively) are stored mostly in the cotyledons. Except for a slight degradation of raffinose and increase in sucrose, there is no detectable reserve mobilisation during germination. The endosperm (8% of seed dry weight), which has thick, mannan-containing cell walls (carbohydrate, 3,4% of seed dry weight), is completely degraded within about 15h following germination. Mannanase activity increases about 100-fold during the same period and arises in all regions of the endosperm. Also during this period sucrose and raffinose are degraded and fructose and glucose accumulate in the embryo. The endosperm hydrolysis products are taken up by the embryo, and are probably used as an additional reserve to support early seedling growth. However, endosperm cell-wall carbohydrates, such as mannose, are not found as free sugars. Lipid and phytate are degraded in a later, second phase of mobilisation. Low levels of sucrose are present in the embryo, mostly in the cotyledons, and large amounts of fractose and glucose (14% of seedling dry weight at 3 days after sowing) accumulate in the hypocotyl and radicle. It is suggested that sucrose, produced in the cotyledons by gluco-neogenesis, is translocated to the axis and converted there to fructose and glucose.     

Early Actions of Gibberellic Acid on the Embryo and on the Endosperm of Avena fatua Seeds

Gibberellic acid at 0.1 μm stimulates amylase synthesis in dormant Avena fatua seeds without inducing germination; at 0.5 mm it enhances biosynthesis of proteins and RNA in both the embryo and the endosperm and utilization of the endosperm sugars by the embryo. These events occur in early hours (0-14th hour) and prior to germination, which begins 24 hours after gibberellic acid application. These observations are in agreemeent with the concept that in cereal grains gibberellic acid has two morphological sites of actions: the embryo and the endosperm, and that germination (radicle protrusion) is not caused by gibberellic acid-induced amylase synthesis in the endosperm.     

Effect of Gibberellic Acid, Kinetin, and Ethylene plus Carbon Dioxide on the Thermodormancy of Lettuce Seed (Lactuca sativa L. cv. Mesa 659)

The effects of gibberellic acid and kinetin with ethylene plus carbon dioxide on the thermodormancy of lettuce seeds (Lactuca sativa L. cv. Mesa 659) at 35 C in the dark were studied. The combination of gibberellic acid plus kinetin with ethylene plus carbon dioxide was most effective in overcoming thermodormancy in these Great Lakes type seeds, alleviating any induced light requirement. Gibberellic acid action required at least a minimal level of ethylene plus carbon dioxide. Kinetin action was independent of ethylene plus carbon dioxide but interacted with the gases when the gases were added. A schematic representation of the interaction is presented.     

二氢血根碱对莴苣幼苗根生长及其细胞分裂的影响

以莴苣幼苗为受体,用培养皿法检测从细果角茴香中分离得到的二氢血根碱对莴苣幼苗根生长和根毛发育的影响,并采用根尖细胞有丝分裂检测和单细胞凝胶电泳法对其可能的作用机制进行了初步研究.结果显示:较低浓度(25、50μmol/L)二氢血根碱能显著促进莴苣根的生长,较高浓度(200、300μmol/L)二氢血根碱显著抑制根的生长;二氢血根碱(10、20、30、40、50μmol/L)对莴苣幼苗根毛发育有极显著的抑制作用,且两者均表现了浓度依赖性.较低浓度(25、50μmol/L)二氢血根碱使根尖细胞有丝分裂指数显著增加,而对根尖细胞DNA没有显著影响;较高浓度(200、300μmol/L)二氢血根碱使根尖细胞有丝分裂指数显著下降,同时根尖细胞DNA受到显著性损伤.研究发现,低浓度的二氢血根碱对莴苣幼苗根生长的促进作用主要是由于根尖细胞有丝分裂活力增加所致;而高浓度二氢血根碱对莴苣幼苗根的抑制作用极可能是由于根尖细胞DNA受到损伤,使得细胞分裂活力降低,分裂期细胞数目减少,从而导致根生长受到抑制.     

Development of Stomata in Lactuca sativa L.

The structure of the epidermis on various parts of the plantof Lactuca sativa Linn. is described. Development of stomatais studied in young leaves and stems. Tognini (1897) has previouslymentioned that the stomata on stems of L. virosa develop froma meristemoid with four cutting faces but the present studypoints out that the meristemoid cuts off only two mesogene neighbouringcells and the two others are perigene.     

Endosperm and Embryo Development in Daucus carota L.

Maximum carrot seed dry weight and maximum endosperm volumewere reached about 35 d after anthesis, although at this timethe endosperm was still soft, the pericarp green and less than50% of the seeds were viable. Fully viable, ripe seeds werenot produced until 44 d later. Seventy per cent of the increasein endosperm volume was due to an increase in cell number, whichceased 35 d after anthesis. The increase in embryo volume wasslower and was due to an increase in both cell number and cellvolume which continued until 49 d after anthesis. At maturitythe embryo was the equivalent of between 2% and 3% of the endospermvolume. The relationship between embryo length and cell number per embryowas unaffected by seed crop plant density, seed crop harvestdate and position of the seed on the mother plant but it wasaffected by the year of seed production, possibly due to differencesin temperature during the period of seed growth. Key words: Endosperm, Embryo, Carrot, Development     

Embryo and Endosperm Metabolism of Barley Seeds during Early Germination

Embryos detached from germinating barley seeds were immersedin tritiated water or solutions containing ¹⁴C-labelled compounds.Amino acids rapidly became radioactive and later acids of theKrebs cycle. Labelled alanine did not give rise to radioactivesucrose.     

The Effect of Arsenate and Other Inhibitors on Early Events during the Germination of Lettuce Seeds (Lactuca sativa L.)

The effect of arsenate, arsenite, 2,4-dinitrophenol, and anaerobiosis on early events in seed germination was investigated using both intact and punched seeds of lettuce (Lactuca sativa L.). It was found that punching the seed removes penetration barriers to the entrance of inhibitors without an undue loss of germination or light responses. The kinetics of the action of germination inhibitors were established by 2-hour pulse experiments. Arsenate and 2, 4-dinitrophenol have very different kinetics. The inhibition of germination in punched seeds by arsenate given in conjunction with phosphate compared with the lack of inhibition of arsenate plus phosphate on the growing seedling, suggest a distinct metabolic change in the germinating embryo at some time between the onset of germination and subsequent seedling growth.     

Regulation of Root Growth in Lactuca sativa L. Seedlings by the Ent-Kaurane Diterpenoid Epinodosin

Epinodosin, an ent-kaurane diterpenoid isolated from Isodon japonica var. galaucocalyx, had a biphasic, dose-dependent effect on root growth and a strong inhibitory effect on root hair development in Lactuca sativa L. seedlings. Lower levels of epinodosin (25–100 μM) significantly promoted root growth, but higher concentrations (150–200 μM), by contrast, had inhibitory effects. In addition, all of the tested concentrations (20–80 μM) inhibited root hair development of lettuce seedlings in a dose-dependent manner. Further investigations on the underlying mechanism revealed that the promotion effect of epinodosin (25–100 μM) resulted from increasing the cell length in the mature region and enhancing the mitotic activity of meristematic cells in lettuce seedling root tips. On the other hand, epinodosin at higher concentrations inhibited root growth by strongly affecting both the cell length in the mature region and the division of meristematic cells. Comet assay analysis demonstrated that the decrease of mitotic activity of root meristematic cells was due to DNA damage induced by higher levels of epinodosin.     

Proteomics Analysis of Embryo and Endosperm from Mature Common Buckwheat Seeds

We used proteomics analysis to generate the profiles of proteins in the endosperm and embryo of common buckwheat grains. These differentially expressed proteins are potentially involved in seed metabolism. Extractions were done by trichloroacetic acid (TCA) precipitation. The resulting proteins were separated using SDS-PAGE coupled to LC-ESI-Q/TOF-MS/MS. This allowed us to detect and identify 67 proteins with isoforms, making this the most inclusive protein profile. The proteins were determined to be functionally involved in the central metabolic pathway of the seed, with metabolic interest being reflected in the occurrence of a tissue-specific enzyme balance. For a case in point, we found a tissue-specific and subcellular compartment-specific isoform of granule-bound starch synthase 1 in the chloroplast/amyloplast. This provided proteomic verification of the presence of a distinct regulatory mechanism for the biosynthesis of glycan and starch, which produce amylase and amylopectin. Furthermore, several previously characterized allergenic proteins such as 11S and 13S globulin seed storage protein were acknowledged in our seed samples, thus representing the potential for proteomics techniques that survey food sources for any incidence of allergens. This protein profile of common buckwheat grain is a new avenue for understanding its seed physiology in dormant stage as well as suggesting commercial applications for the buckwheat industry as buckwheat flour.     

Enhancement of Gibberellic Acid-stimulated Hypocotyl Elongation of Lettuce (Lactuca sativa L. cv. Grand Rapids) by Phlorizin and Light

The interaction of light, gibberellic acid (GA₃), and phlorizinin the growth of lettuce (Lactuca sativa L. cv. ‘GrandRapids’) hypocotyls was investigated. At all concentrationsof GA₃, phlorizin enhanced GA₃-induced growth at luminous intensitiesabove 50 ft-c (continuous light). Without GA₃, phlorizin hadno effect on hypocotyl growth in the light but it inhibitedgrowth in the dark. Both seedlings and hypocotyl sections respondedto phlorizin in the presence of GA₃. There was no iteractionbetween phlorizin and KCl. Water-growth was severly inhibitedby light. GA₃,-induced growth was slightly inhibited by light,and then only at luminous intensities above 50 ft-c. Thus, relativeto H₂O-growth, GA₃-induced growth increased with increasingluminous intensity up to 450 ft-c, where it reached saturation.It seems that a synergism may exist between light and GA₃ aswell as between phlorizin and GA₃. Lactuca sativa L, lettuce, hypocotyl elongation, gibberellic acid, phlorizin, light