A Histological Study of Development of Adventive Embryos in Organ Cultures of Phoenix dactylifera L.

Callus cultures from axillary buds of 2–4-year-old offshootsof Phoenix dactyl'fera L have yielded plantlets adventitiouslyAdventive embryos originated from meristematic cytoplasm-richcells located in the epidermal and adjacent sub-epidermal portionsof the periphery of callus on a basal medium supplemented with2, 4-D and isopentenyladenine The formation of adventive embryosis described Morpho-genetically competent cells proliferateinto globular proembryos which differentiate into bipolar structures.Transfer to a medium devoid of hormones enhances embryo developmentand promotes plantlet growth Comparative studies were made betweenzygotic and adventive embryos in various stages of development Phoenix dactylifera L, date palm, Palmae, adventive embryogenesis, histological development     

Embryogenic Callus Induction from Coffea arabica Leaf Explants by Benzyladenine

Coffea arabica leaf explants cultured on medium with 5 µM6-benzyladenine (BA) as the sole plant growth regulator producedwhite friable calluses that formed somatic embryos. These calluseshave been subcultured on the same medium for more than 2 yearsand maintain the ability to produce somatic embryos. (Received October 3, 1984; Accepted January 18, 1985)     

The Rate of Morphogenesis of Embryos and Seeds in Four Species of Grain Legumes

Comparative embryo development has been studied histologicallyin Lupinus albus, Lupinus mutabilis, Vicia faba, Pisum sativumand Latkyrus latifolius. The detailed histology of the stagesof embryo formation up to the early differentiation of tissuesof the seed is reported. The rate of embryogenesis has beentimed through 15 stages of development from anthesis and comparativerates of tissue formation established between the species. Themain observation was the slow rate of morphogenesis of embryosand seeds in Lupinus albus in comparison with the very rapidrate observed in Pisum sativum. A long period at the globularembryo stage, when embryo morphogenesis was inactive contributedto the extended development time of embryos and seeds in Lupinusalbus. Slow differentiation of reproductive tissues in L. albusdetermines late maturity in seeds and pods. Lupinus albus, white lupin, L. mutabilis, tarwi, Vicia faba, faba bean, Pisum sativum, pea, Lathyrus latifolius, everlasting pea, embryo development     

Somatic embryogenesis, scanning electron microscopy, histology and biochemical analysis at different developing stages of embryogenesis in six date palm (Phoenix dactylifera L.) cultivars

An efficient somatic embryogenesis system has been established in six date palm (Phoenix dactylifera L.) cultivars (Barhee, Zardai, Khalasah, Muzati, Shishi and Zart). Somatic embryogenesis (SE) was growth regulators and cultivars dependent. Friable embryogenic callus was induced from excised shoot tips on MS medium supplemented with various auxins particularly 2,4-dichlorophenoxyacetic acid (2,4-D, 1.5 mg 1^−l). Suspension culture increased embryogenesis potentiality. Only a-naphthaleneacetic acid (NAA, 0.5 mg 1⁻¹) produced somatic embryos in culture. Somatic embryos germinated and converted into plantlets in N⁶-benzyladenine (BAP, 0.75 mg 1^−l) added medium following a treatment with thidiazuron (TDZ, 1.0 mg 1^−l) for maturation. Scanning electron microscopy showed early stages of somatic embryo particularly, globular types, and was in masses. Different developing stages of embryogenesis (heart, torpedo and cotyledonary) were observed under histological preparation of embryogenic callus. Biochemical screening at various stages of somatic embryogenesis (embryogenic callus, somatic embryos, matured, germinated embryos and converted plantlets) of date palm cultivars has been conducted and discussed in detail. The result discussed in this paper indicates that somatic embryos were produced in numbers and converted plantlets can be used as a good source of alternative propagation. Genetic modification to the embryo precursor cell may improve the fruit quality and yield further.     

Cryopreservation of oil palm (Elaeis guineensis Jacq.) somatic embryos involving a desiccation step

Summary The standard cryopreservation process previously developed for oil palm clones using shiny white, finger-like somatic embryos could be applied in some cases to standard cultures. Its efficiency was markedly improved by completing the 7-day pregrowth period on 0.75 M sucrose by an additional dehydration period carried out either by placing the embryos in the air current of the laminar flow cabinet or in an air tight box containing silica gel. This improved process was successfully applied to 7 different clones. It will facilitate the routine uof cryopreservation for oil palm cultures.     

Histology of Somatic Embryogenesis from Leaf Explants of the Oil Palm Elaeis guineensis

Histological analysis was carried out during the sequence ofevents which lead to the obtaining of somatic embryos of oilpalm. Calluses from the division of perivascular cells formedat the veins of young leaf explants. Subsequent proliferationof histologically similar nodules was by means of a cambium-likezone. Under certain conditions these calluses consisted almostentirely of meristematic cells. They then differentiated rapidly:the cambium-like zone fragmented, leading to protuberance inwhich the cells divide rapidly; epidermal structures were formed,with a network of procambial strands, and synthesis of storagelipids accompanied the formation of these embryo-like structureswhich developed into clumps of true somatic embryos, each witha shoot apex and a root apex. Other structures frequently observedduring in vitro culture are also described and show that alternatepathways do exist. The structure and evolution of somatic embryosare compared to those of zygotic embryos. Storage lipids emergeas an early tracer of the satisfactory development of tissuetowards somatic embryogenesis. Oil palm, Elaeis guineensis, histology, somatic embryogenesis, callogenesis, storage lipids     

Somatic Embryogenesis in Cassava: The Anatomy and Morphology of the Regeneration Process

Anatomical and morphological studies demonstrated that somaticembryos developed similarly on mature seed and clonal leaf explantsof cassava (Manihot esculenta Crantz) cultured for 20–24d on Murashige and Skoog (MS2) basal medium supplemented with4.0 mg l^–1 2,4-D (Stage 1) before transfer to MS2 basalmedium supplemented with 0–01 mg l^–1 2,4-D and 0–1mg l^–1 6-benzylaminopurine (Stage II medium). Within 7d of inoculation onto Stage I medium, cell divisions occurredin the adaxial tissues of cotyledon-piece and leaf-lobe explants,and associated with this was the development of embryogeneticprotusions and ridges on the adaxial surface. Foliose structuresand somatic embryo initials developed from these tissues oncotyledon, embryonic axis and leaf-lobe explants and, when cultureswere transferred to Stage II medium, further somatic embryodevelopment occurred. Somatic embryos apparently originatedfrom groups of cells and were identified by the presence ofa closed root axis, a shoot axis and cotyledons of similar shapeand venation to those of zygotic embryos. Somatic embryos hadno vascular connection with parental cultures. Manihot esculenta, cassava, somatic embryogenesis, tissue culture, anatomy, morphology, morphogenesis     

Dried Cryopreserved Somatic Embryos of Two Picea Species Provide Suitable Material for Direct Plantlet Regeneration and Germplasm Storage

The present study aimed to develop a cryopreservation methodfor long-term storage of mature somatic embryos of Picea spp.The effects of drying rate, embryo water content prior to cryopreservation,thawing rate, and rehydration on survival of cryopreserved somaticembryos were investigated. Emphasis was placed on the capacityof cryopreserved somatic embryos to germinate and regenerateplantlets directly, or to reinduce embryogenic tissue for newembryo production. Firstly, a slow drying rate at 97 or 88%relative humidity (RH) was needed to achieve high germination(96.7–100%) and high plantlet conversion rates (26.7–46.7%)(not different from controls). Secondly, somatic embryos hadto reach a water content of 0.23 g H₂O g^-1d.wt (48 h of desiccationat 97% RH) before immersion in liquid nitrogen to germinateat high frequency (93.8%). Thawing techniques had no effecton embryo survival. Dried and cryopreserved somatic embryosof Picea can also be used to reinduce embryogenic tissue andstart new embryo production. Best reinduction frequency (66.7%)was obtained from cryopreserved embryos dried at 97% RH andrehydrated at 100% RH for 12 h prior to reinduction. No differencein embryo production was noticed between the parent line (1stembryogenic cycle) and the sub-lines (2nd embryogenic cycle).Second generation embryos germinated and regenerated into plantletsat rates similar to controls. The optimal cryopreservation methodwas successfully applied to severalP. mariana and P. glaucagenotypes. Copyright 2000 Annals of Botany Company Picea mariana(Mill) B.S.P., Picea glauca(Moench) Voss, desiccation, embryo water content, thawing, rehydration, embryogenic tissue, genotypes, conifers, clonal propagation     

Non-Stomatal Inhibition Associated with Inactivation of Rubisco in Dehydrated Coffee Leaves under Unshaded and Shaded Conditions

The effect of rapid dehydration due to withholding of irrigationon leaf photosynthesis in coffee (Coffea arabica L.) was studiedby comparing the CO₂-dependent rate of photosynthesis in intactleaves (A/Ci curve), the amounts of Chl, total soluble proteinand ribulose-l,5-bisphosphate carboxylase (Rubisco) in leaves,and the activities of photochemical reactions of isolated chloroplastsand of Rubisco under unshaded and shaded conditions. The CO₂-saturatedrate of photosynthesis and the carboxylation efficiency (theinitial slope of A/Ci curve) decreased with decreasing leafwater potential (     

Abscisic Acid and Assimilate Partitioning to Developing Seeds: III. DOES ABSCISIC ACID INFLUENCE SUGAR RELEASE FROM ATTACHED EMPTY SEED COATS IN AN ABA-DEFICIENT PISUM SATIVUM MUTANT?

Influence of abscisic acid on the release of sucrose from surgicallymodified Pisum sativum ovules was studied with the use of awilty pea mutant and variations in the amount of available assimilates.Phloem import was unaffected by applied ABA, independent ofthe endogenous ABA level and source-limited conditions. Key words: Pisum sativum, abscisic acid, ABA-deficient (wil) mutant, assimilate partitioning, empty-seed-coat technique     

Stomata on the Primary Root of Pisum sativum L.

The first record of stomata on a non-specialized root was obtainedby scanning electron microscopy of 4-d-old Pisum sativum L.In some cases subsidiary cells were trichoblasts. Stomata andthe root triarch vascular structure were simultaneously presentin transverse sections through the root. Pisum sativum, pea, root stomata, guard cells, trichoblasts     

Ultrastructural Evidence for the Effects of Freezing in Embryonic Axes of Pisum sativum L. at Various Water Contents

This study investigated the effects of rapid drying (in an airstream) and rapid freezing (in sub-cooled liquid nitrogen) onthe survival and ultrastructural preservation of pea embryonicaxes that had been imbibed for 4 h (desiccation tolerant) and24 h (desiccation sensitive). Maximum survival of all axes inthe absence of freezing was attained. Similarly, 100% survivalwas obtained if freezing was preceded by rapid drying. Axesimbibed for 24 h and not dried were more sensitive to freezingthan undried, 4 h imbibed axes. Ultrastructural examinationshowed no organellar or cytomatrical deformations in axes fromany of the treatments. Some cells of the 24 h imbibed axes showedlocalized plasmalemma abnormalities after railed dehydration.Subsequent to freezing, irregular nuclei were observed and plasmalemmavesiculation occurred. If these axes were not dried prior tofreezing, plasmalemma vesiculation became prominent, clumpingof the cytoskeleton occurred and some wall abnormalities becameapparent. Rapid drying probably increases intercellular soluteconcentrations, and sub-cooled liquid nitrogen will increasethe rate of heat exchange between tissue and cryogen. A combinationof rapid drying and rapid freezing may obviate, or reduce, therequirement for cryoprotectants on freezing of desiccation sensitivetissue.Copyright 1995, 1999 Academic Press Pisum sativum L., pea, embryonic axis, ultrastructure, transmission electron microscopy, cryopreservation, rapid freezing     

Orthodox Behaviour of Oil Palm Seed and Cryopreservation of the Excised Embryo for Genetic Conservation

Desiccation experiments have shown the oil palm seed to be orthodox,not recalcitrant, in character. There is a significant differencein water content between the whole seed and the embryo whichis maintained despite desiccation, and results in the failureof sub-zero storage of whole seeds. The successful recoveryof viable, excised embryos from liquid nitrogen, and their subsequentregrowth in vitro, suggests a practical technique for the longterm conservation of the genetic resources of the species. Elaesis guinensis L, oil palm embryo, cryopreservation, recalcitrant seed     

Amino Acid Release from the Seed Coat of Developing Seeds of Vicia faba and Pisum sativum

After removal of the embryo from developing ovules of Viciafaba L. and Pisum sativum L., seed-coat exudates were collectedand the amino acid fraction of the exudate was analyzed. InV. faba, alanine was the most important compound of the aminoacid fraction. In P. sativum, alanine and glutamine were thetwo most important components, whereas only small amounts ofasparagine were present. Comparison with published data suggeststhat seed-coat exudates may differ from phloem sap in the relativeimportance of these amino acids. Pisum sativum, pea, Vicia faba, broad bean, amino acid transport, amino acid unloading, seed-coat exudate, seed development     

Identification of a Novel Triterpenoid Saponin from Pisum sativum as a Specific Inhibitor of the Diguanylate Cyclase of Acetobacter xylinum

A specific and highly potent inhibitor of diguanylate cyclase,the key regulatory enzyme of the cellulose synthesizing apparatusin the bacterium Acetobacter xylinum, was isolated from extractsof etiolated pea shoots (Pisum sativum). The inhibitor has beenpurified by a multistep procedure, and sufficient amounts ofhighly purified compound (3-8 mg) for spectral analysis wereobtained. The structure of this compound was established as3-O-a-L-rhamnopyranosyl-(l     

Somatic embryogenesis and analysis of peroxidases inPhoenix dactylifera L

To determine some physiological parameters implicated in somatic embryogenesis in date palm (Phoenix dactylifera L.), peroxidases have been studied. Activated charcoal commonly used in date palm tissue culture as an essential antibrowning factor decreased cellular protein contents and peroxidase activities. During the first months of culture, the conventionally used medium (100 mg dm^?3 of 2,4-dichlorophenoxyacetic acid, 3 g dm^?3 charcoal) reduces 2 to 3 and 4 to 6 times protein contents and peroxidase activities, respectively, in comparison with the same one containing only 5 mg dm^?3 of 2,4-D and with or without 150 mg dm^?3 charcoal. In addition, the standard procedure decreased the embryogenic potential which is positively related to the intra- and extracellular (excreted into culture medium) peroxidase activities. In medium with embryogenic calli, extracellular peroxidase activity was three times as high as the activity determined in the same medium with non-embryogenic calli. There were two basic isoforms and four to five acidic bands characterizing the embryogenic calli. It can be suggested that peroxidases play a key role in somatic embryogenesis of date palm and the charcoal used at 3 g dm^?3 constitute a perturbating factor for this process.     

Theoretical Basis of Protocols for Seed Storage III. Optimum Moisture Contents for Pea Seeds Stored at Different Temperatures

In previous work, we demonstrated that there was an optimummoisture level for seed storage at a given temperature (Vertucciand Roos, 1990), and suggested, using thermodynamic considerations,that the optimum moisture content increased as the storage temperaturedecreased (Vertucci and Roos, 1993b). In this paper, we presentdata from a two year study of aging rates in pea (Pisum sativum)seeds supporting the hypothesis that the optimum moisture contentfor storage varies with temperature. Seed viability and vigourwere monitored during storage under dark or lighted conditionsat relative humidities between 1 and 90%, and temperatures between-5 and 65°C. The optimum moisture content varied from 0·015g H₂O g^-1 d.wt at 65°C to 0·101 g H₂O g^-1 d.wt at15°C under dark conditions and from 0·057 at 35°Cto 0·092 g H₂O g^-1 d.wt at -5°C under lighted conditions.Our results suggest that optimum moisture contents cannot beconsidered independently of temperature. This conclusion hasimportant implications for 'ultra-dry' and cryopreservationtechnologies.Copyright 1994, 1999 Academic Press Seed storage, seed aging, seed longevity, water content, temperature, glass, desiccation damage, ultradry, Pisum sativum L., pea, cryopreservation     

Identification of Shoot Apical Meristem Cells Committed to Form Vascular Elements in Pisum sativum L. and Vicia faba L.

A cytochemical study of naphthol AS-D esterases in vegetativeshoot apices of Pisum sativum and Vicia faba L. has shown thepresence of carboxyl esterases (E.C. 3.1.1.1 [EC] .) in those meristemcells already committed to form vascular elements. These cellsform a sequence linking the morphologically identifiable procambiumto the cells of the tunica layers at a site either already identifiableas the next primordium or which will form the next primordium.The implications of this result are briefly discussed in relationto the control of primordia formation and procambial cell development. Pisum sativum, Vicia faba, determination, vascular tissue, shoot apex, cytochemistry     

Somatic embryogenesis and regeneration of plantlets in protoplast cultures from somatic embryos of coffee (Coffea canephora P. ex Fr.)

Somatic embryogenesis was achieved in protoplast cultures of coffee. Protoplasts were isolated from cell suspension-derived somatic embryos of Coffea canephora. After repeated subculture in a medium supplemented with 0.5 mg/l of each of kinetin, 2,4-dichlorophenoxyacetic acid (2,4-D), and naphthaleneacetic acid (NAA), microcalli developed. Transfer of these microcalli to a medium lacking growth regulators resulted in the formation of globular embryos. Upon subculture without growth regulators they grew to well-differentiated embryos, Eventually some of them developed to plantlets which were transferred to the greenhouse for further observation.     

Purine Alkaloids of the Fruits of Camellia sinensis L. and Coffea arabica L. during Fruit Development

The amounts of two purine alkaloids, caffeine and theobromine,in the fruit of tea (Camellia sinensis L.) increased markedlyduring the growing season until the fruit was full-ripened anddried. In the dry fruit, the pericarp contained the most alkaloids,but there were also considerable amounts in the seed coat and,to a lesser extent, the fruit stalk and the seed. The shed seedsalso contained significant amounts of the alkaloids, especiallyin the seed coats. In contrast with the dry fruit of tea, seedsand pericarp of coffee (Coffea arabica L.) fruit contained aconsiderable amount of caffeine and a small amount of theobromide.A small amount of theophylline was also present in the pericarpof the ripened fruit. Relationships between growth and purinealkaloid content in tea and coffee fruits and their roles duringseed formation are discussed. Camellia sinensis L., tea, Coffea arabica L., coffee, purine alkaloids, fruit development, seed, seed coat, caffeine, theobromine, theophylline