An Analysis of Seed Development in Pisum sativum II. The Effect of the r-Locus on the Growth and Development of the Seed

The r-locus is one of the few genetic loci known to affect thestorage product composition and the morphology of pea (Pisumsativum) seeds. Lines which are near-isogenic except for ther-locus have been developed to study the effects of this locuson seed development. The plant phenotypes of these lines werevery similar except for those characteristics previously attributedto the r-locus. The seed development of the two lines followedsimilar patterns until the endosperm was absorbed by the embryo.The fresh weight of the rr line then increased more rapidlydue to the overall effect of a higher rate of water uptake anda lower rate of dry weight increase of the rr embryos comparedwith embryos homozygous for the R-allele. The effect of the r-locus on the relationship between embryofresh weight and dry weight suggests that the alleles may beaffecting the osmotic regulation of the developing embryo. Pisum sativum, pea, seed development, r-locus, genetic variation, growth analysis     

Embryology of Early Abortion Due to Limited Maternal Resources in Pisum sativum L.

In most flowering plants, many embryos are aborted early intheir development due to limited maternal resources. The kin-conflictinterpretation of plant embryology predicts these abortionsshould be under maternal control. In a study of the abortionprocess in Pisum sativum, we found the first visible indicationof abortion was formation of a weak hypostase. Callose was locallydeposited around the chalazal endosperm haustorium, and ligninalong the outer cell walls of the remnant nucellar tissue. Thenucellus was compressed by proliferating adjacent inner integumentalcells. The endosperm haustorium's cytoplasm was forced backinto the embryo sac cavity. With suppression of haustorial activitythe endosperm nuclei gradually enlarged followed by enlargementof the embryo and suspensor nuclei. Finally, nuclei and cytoplasm throughout the endosperm and embryolost stainability and broke down. Four successive stages wererecognized in seed abortion. In seeds developing to maturity,no hypostase was developed and the haustorium continued to digestboth the remnant nucellus and the proliferated inner integumentalcells. These observations are consistent with the kin-conflicthypothesis. Pisum sativum, garden pea, ovule abortion, histology, hypostase, kin-conflict hypothesis     

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     

Characteristics of Sugar, Amino Acid and Phosphate Release from the Seed Coat of Developing Seeds of Vicia faba and Pisum sativum

After removal of the embryo from developing seeds of Vicia fabaL. and Pisum sativum L., the ‘empty’ ovules werefilled with a standard solution (pH 5.5). Seed coat exudatesof both species were collected during relatively long experiments(up to about 12 h) and the concentration of sugar (mainly sucrose),amino acids and phosphate in the exudate measured. A discussionis presented on the amino acid/sugar ratio and the phosphate/sugarratio in the seed coat exudate. A pretreatment (15 min) withp-chloromercuribenzenesulphonic acid (PCMBS) reduced the releaseof sugar, amino acids and phosphate from broad bean seed coats.After excision of ‘empty’ ovules of Vicia faba andPisum sativum from the maternal plant, 2–4 h after thistreatment a strong difference became visible between sucroserelease from excised seed coats and sucrose release from attachedseed coats. Similarly, when the rate of phloem transport ofsucrose into an ‘empty’ ovule of Vicia faba or Pisumsativum was reduced by a sub-optimal mannitol concentrationin the solution, a reduced rate of sugar release from the seedcoat could be observed. Excision and treatment with a sub-optimalmannitol concentration reduced the release of amino acids toa lesser extent than for sucrose. These treatments did not reducethe rate of phosphate release from the seed coat. Key words: Seed development, Seed coat exudate, Phloem transport     

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     

Functional Significance of Acid Phosphatase Distribution During Embryo Development in Pisum sativum L

The distribution of P₁, ester P and acid-insoluble nucleic acidP has been studied in relation to acid phosphatase activity(EC 3. 1. 3. 2) in the component parts of developing pea seeds(Pisum sativum L.). Despite the favourable pH of the liquidcontents of the embryo sac (pH 5.5), only very low acid phosphataseactivity was detected in this fluid (c. 0.01 units per seed).Potential substrates for phosphatase action were in fact absentfrom the secretion, the only form of P present being P_i, inconcentrations up to 8 mM. The data support the hypothesis thatthe high acid phosphatase activities which develop in the seed-coatsare involved in regulating the supply of P as P₁ to the developingembryo. Pisum sativum L., pea, embryo development, acid phosphatase, phosphorus, seed-coats, seed development     

Effect of the Osmotic Environment on K+ and Mg2+ Release from the Seed Coat and Cotyledons of Developing Seeds of Vicia faba and Pisum sativum. Evidence for a Stimulation of Efflux from the Vacuole at High Cell Turgor

After removal of the embryo from developing seeds of Vicia fabaL. and Pisum sativum L., the ‘empty’ ovules werefilled with a substitute medium (pH 5.5) and the effect of theosmolality of the medium on K⁺ and Mg²⁺ release from the seedcoat was examined. In long-term experiments (12 h or longer),with both attached and detached seed coats, the rate of K⁺ andMg²⁺ release from seed coats filled with a solution withoutosmoticum was enhanced, in comparison with release from seedcoats filled with a solution containing 400 mol m     

Effect of Potassium on Sucrose and Amino Acid Release from the Seed Coat of Developing Seeds of Pisum sativum

After removal of the embryo from developing seeds of Pisum sativum,the ‘empty’ ovules (seed coats without enclosedembryo) were filled with a solution (pH 5.5) containing mannitol(usually 400 mM) to which various salts were added. A solutioncontaining two isotopes ((a) [²H]-sucrose/[–¹⁴C]aminoisobutyricacid (AIB) or (b) [³H]valine/[₁₄C]asparagine mixture) was administeredto the plant via the petiole subtending the fruiting node, and[²H]solute and [¹⁴C]solute unloading from the seed coat wasmeasured, in pulse-labelling experiments of about 5 h. The presenceof 25 or 50 mM K⁺ in the ‘empty’ ovule enhancedthe release of sucrose from the seed coat particularly duringthe first hours of the experiment, but the stimulating effectof K⁺ on the release of labelled solutes derived from aminoacids was much smaller. The presence of 25 mM CaCl₂ did notaffect the release of sucrose or amino acids from the seed coat.The effect of K⁺ on sucrose and amino acid release is explainedas an inhibition of sucrose and amino acid resorption from theseed coat apoplast into seed coat cells, after unloading fromthe seed coat unloading sites. It is suggested that amino acidrelease is much less affected by K⁺ than sucrose release, becausefar less resorption of amino acids by seed coat parenchyma cellstakes place during amino acid transport into the seed coat cavity. Pisum sativum, pea, assimilate transport, assimilate unloading, seed-coat exudate, seed development, sucrose resorption, surgical treatment     

An analysis of seed development in Pisum sativum XIX. Effect of mutant alleles at the r and rb loci on starch grain size and on the content and composition of starch in developing pea seeds

The effects of mutant alleles at the r and rb loci on starchgrain size and the levels of starch and amylose in developingpea (Pisum sativum L.) seeds have been examined. Four lines,near-isogenic except for genes at these loci, have been usedto show that both mutations reduce levels of starch throughoutembryo development and reduce levels still further when combinedin the ‘double mutant’. The reduction in starchcontent was due, at least in part, to a reduction in starchgranule size. Although the proportion of starch in mature embryoswas similar in the rrRbRb and RRrbrb lines, the starch contentdiffered between these two lines during development, as a percentageof embryo dry weight. This difference was due to a reductionin the absolute growth of the embryo caused by the rb mutation.Lines homozygous for the mutant r allele with either wild-type(RbRb) or mutant (rbrb) alleles at the rb locus contained increasedproportions of amylose in their starch throughout development,due to a reduced production of amylopectin. The presence ofthe rb mutation, however, also reduced the amount of amylosein relation to the reduction in total starch levels. Mutantalleles at both loci also reduced starch levels in the testaduring development, the reduction due to rb being more extreme.Reciprocal crosses showed a maternal effect of the rb mutationon final seed size and on the absolute amount of starch in theembryo. Key words: Pisum sativum L., seed, starch, development, mutant     

Seed and Pod Wall Development in Pisum sativum, L. in Relation to Extracted and Applied Hormones

Developing fruits of Pisum sativum, L., cv. ‘Alaska’,contain relatively large amounts of hormones, mainly concentratedin the embryos and liquid endosperm. A close relationship canbe demonstrated between changes in extractable amounts of gibberellins(mainly GA₂₀), auxins (methyl 4-chloroindol-3yl acetate andprobably 4-chloroindol-3yl acetic acid), and abscisic acid,and changes in growth rates of both the pod wall and seeds.Growth of the pod wall appears to depend largely on hormonessupplied by the seeds. Marked changes in the germination capacity of the maturing seedsare closely associated with changes in extractable amounts ofmethyl-4-chloroindol-3yl acetate and abscisic acid. It is believedthat high concentrations of these substances in the embryo,rather than any restriction imposed by the testa, may preventprecocious germination of the seeds     

Metabolism of Phloem-borne Amino Acids in Maternal Tissues2Pisum sativum L.)

The amino acid composition of the EDTA-induced phloem exudatereaching the fruit and the seed, and of the solutes releasedby the seed coat during fruit development were determined inglasshouse-grown pea (Pisum sativum L. cv. Finale) suppliedeither with nitrate-free nutrients (nodulated plants) or withcomplete medium (non-nodulated plants). The EDTA-promoted exudationtechnique was used supposedly to collect phloem sap and theempty seed technique supposedly to collect the solutes secretedby the seed coat to the embryo sac cavity. In young seeds embryosac liquid was sampled directly from the embryo sac. The maincarbohydrate transported and secreted was sucrose. The mainamino acids reaching the fruit were asparagine, glutamine, andhomoserine. Their proportions were steady during a day-nightcycle and throughout fruit development. Amino acid compositionchanges occurred first in the pathway from fruit stalk to seedfunicle, due to the formation of threonine (probably from homoserine)and in the seed coat due to production of glutamine, alanineand valine which, together with threonine were the main secretedamino acids. The temporary nitrogen reserves of the pod walland seed coat were remobilized as asparagine during senescence.Phloem exudate of nodulated plants showed a higher (about twice)proportion of asparagine but lower proportions of homoserineand glutamine than in EDTA-induced phloem exudate of nitrate-fedplants. The two types of nitrogen nutrition also produced somechanges in relative proportions of threonine and homoserinesecreted by the seed coat. Key words: Pisum sativum, phloem, amino acids, pod wall, seed coat     

Embryo and Endosperm Function and Failure inSolanumSpecies and Hybrids

Although the importance of the endosperm as a food store inmany angiosperm seeds is well known, its significance duringearly embryogenesis has been neglected. In many interspecifichybrids, and in some other situations, embryos do not developfully and abort. It has often been stated that this is causedby the endosperm failing to conduct sufficient nutrients tothe embryo, but seldom has it been suggested that the endospermactively controls most of the early stages of morphogenesisof the embryo. Information gleaned from a broad survey of theliterature, combined with additional evidence presented here,obtained fromSolanum incanumand interspecific hybrids, indicatethat the endosperm is dynamic and very active in regulatingearly embryo development. This requires highly integrated geneticcontrol of rapidly changing metabolism in the endosperm. Ininterspecific hybrids, lack of coordination may cause unbalancedproduction of growth regulating substances by the endospermand hence abortion of the embryo, or even unregulated productionof nucleases and proteases resulting firstly in autolysis ofthe endosperm and then digestion of the embryo. The endospermmay thus serve to detect inappropriate hybridization of speciesor ploidy levels and so prevent waste of resources by producingseeds that would result in sterile hybrids or unthrifty subsequentgenerations. This discriminatory function of the endosperm hasdiminished during evolution and domestication of the crop plantSolanummelongenaL.Copyright 1998 Annals of Botany Company Solanum, embryo morphogenesis, endosperm, hybrid, seed development.     

Cytokinin Content of Pea Seeds during their Growth and Development

Seed development in Pisum arvense L. cv. New Zealand Maple has been studied in relation to changes in level of total endogenous cytokinins. Growth of both the whole seed and the embryo is diauxic, having two phases of active growth separated by a lag period. The two maxima in the growth rates of the whole seed and the embryo occur about the 23rd and 31st days after anthesis. The lag period occurs between days 26 and 28. Cell division is thought to have ceased prior to day 19 and the changes in total cytokinin content in pea seeds after this time are believed to be largely independent of cell division. The three maxima in the cylokinin content per gm. fresh weight of seed and per seed were found to be coincident with the maximum volume of endosperm per seed and the two maxima in the growth rates of the whole seed and the embryo.     

Endosperm Development in Solanum nigrum L. Formation of the Zone of Separation and Secretion

Endosperm development in Solanum nigrum was ab initio cellular.During early seed development, a Zone of Separation and Secretion(ZSS) differentiated within the endosperm. There were threephases in the formation of the ZSS. Phase I—stainabilityof the cell walls and middle lamella increased followed by numeroussmall plasmalemma invaginations (blebs) which became filledwith a fibrillar material. Phase II—the plasmalemma withdrewfrom the cell wall as a fibrillar lipo-carbohydrate matrix accumulatedoutside the plasmalemma. The middle lamella was gradually removedfrom between the cells forming the central axis of the cone.Phase III—the lipo-carbohydrate matrix continued to accumulateoutside the plasmalemma and also within the developing intercellularspaces. Some axial cells were completely separated from theremaining ZSS cells and became embedded in the matrix. The formationof the ZSS did not entail the destruction of the endosperm cellsand cell divisions were frequent. The ZSS was initially cone-shaped,capping the globular embryo. As the embryo sac enlarged, theZSS continued to differentiate. This resulted in a narrow curvedcorridor through the peripheral region of the endosperm whichterminated above the vascular trace. The embryo grew throughthe centre of the ZSS and pushed aside the separated axial cells.The ZSS facilitated the growth of the embryo through the restof the endosperm.Copyright 1993, 1999 Academic Press Lipo-carbohydrate matrix, extracellular matrix, endosperm development, Solanum nigrum, Zone of Separation and Secretion     

Use of the Expolinear Growth Model to Analyse the Growth of Faba bean, Peas and Lentils at Three Densities: Predictive Use of the Model

The expolinear equation for crop growth (Goudriaan and Monteith,Annalsof Botany66: 695–701, 1990; Goudriaan, 1994. In: MonteithJL, Scott RK, Unsworth MH, eds.Resource capture by crops.Nottingham:Nottingham University Press, 99–110) has the potentialto predict growth under specified environmental conditions.The choice of suitable parameters is discussed and tested usingdata from field experiments with faba bean, peas and lentils(Ishag and Dennett,Annals of Botany82: 497–505. 1998).It is suggested that suitable parameters for predicting cropgrowth are the fraction of solar radiation intercepted at emergence,the extinction coefficient for solar radiation, the maximumfraction of radiation intercepted, the maximum relative growthrate and the maximum crop growth rate for a crop interceptingall the incident radiation. In the experiments considered, thedifferences in growth patterns were due mainly to differencesin the maximum relative growth rate associated with differencesin temperature.Copyright 1998 Annals of Botany Company Expolinear equation, grain legumes, crop growth rate, crop density, relative growth rate, growth modelling, faba bean,Vicia fabaL., peas,Pisum sativumL., lentils,Lens culinarsMedic.     

Endogenous cis,trans-Abscisic Acid and Pea Seed Development: Evidence for a Role in Seed Growth from Changes Induced by Temperature

Measurements were made using GC/MS SIM¹ of the effects of temperatureon cis,trans-ABA levels in developing ovules and embryos oftwo pea genotypes contrasted in seed size. These effects werethen related to differences in the growth of the pods, seeds,embryos, and testae. In both genotypes high temperatures hastenedthe onset and rate of logarithmic and then linear growth, greatlyshortening the duration of pod and seed development but withoutgreatly altering seed size. Cis,trans-ABA was most concentratedxin the ovules immediately after fertilization. It also accumulatedin the embryo, more rapidly in the larger-seeded line, duringseed maturation. The stage when accumulation in the embryo beganwas the same irrespective of temperature. Accumulation ceasedwhen the pods started to desiccate. The effects of differentconstant temperatures on the maximum levels of embryo cis,trans-ABAwere relatively small and confounded in one genotype by variationin ovule abortion and in the other by differences in the stagewhen cis,trans-ABA accumulation ceased. However, when plantswere transferred from 13 °C to 29 °C at two differentstages during seed maturation, further seed growth was greatlyinhibited coincident with a substantial increase in embryo cis-trans-ABA.The results suggested a role for cis,trans-ABA in the controlof cotyledon enlargement during the linear phase of seed growth.     

An Analysis of Seed Development in Pisum sativum XVII. The Effect of the rb Locus Alone and in Combination with r on the Growth and Development of the Seed

Near-isogenic lines have been produced in pea to examine theeffects of genes at the r and rb loci on the growth and developmentof the seed. The rb alleles were found to have an effect onthe growth of the testa as well as on that of the embryo incontrast to those at the r locus which only affect the latter.The relationship between the fresh and dry weights of the embryosof rb isoline and the double mutant differed from that of theround-seeded wild-type line. Furthermore, for this relationship,the double mutant line very closely resembled the rr isoline.Copyright1994, 1999 Academic Press Embryo, growth, pea, Pisum sativum L., rugosus loci, seed development, testa, wrinkled-seeded     

Leaf Primordium Initiation and Expanded Leaf Production are Co-ordinated through Similar Response to Air Temperature in Pea (Pisum sativumL.)

Accurate prediction of the timing of leaf area development isessential to analyse and predict the responses of crops to theenvironment. In this paper, we analyse the two processes determiningthe chronology of leaf development—initiation of leafprimordia by the shoot meristem and production of expanded leavesout of the shoot tip—in several pea (Pisum sativumL.)cultivars in response to air temperature and plant growth rate.Contrasting levels of air temperature and plant growth rateduring leaf development were induced by a wide range of sowingdates and plant densities in glasshouse or field experiments.Full leaf expansion was found to occur one phyllochron afterfull leaf unfolding, whatever the leaf nodal position. Primordiuminitiation and expanded leaf production rates presented similarquantitative responses to air temperature (linear response andcommonx-intercept), whatever the plant growth rate, cultivaror period of cycle. As a consequence, they were co-ordinatedand the numbers of initiated primordia or expanded leaves wereeasily deduced from simple visual observation of leaf unfolding.The change, over time, of the numbers of initiated leaf primordiaand fully expanded leaves correlated with cumulated degree-days,with stable relationships in a wide range of environmental conditions.Two phases, with different production rates, had to be considered.These results allowed us to predict accurately the beginningand the end of individual leaf development from daily mean airtemperatures. The relationships obtained here provide an effectiveway of analysing and predicting leaf development responses tothe environment. Pisum sativumL.; pea; number of leaf primordia; number of leaves; temperature; modelling     

The Effect of Artificial Wind on the Growth-rate of Plants in Water Culture: With Plate and three Figures in the Text

Young plants of Brassica napus (rape), Hordeum vulgare, andPisum sativum growing in water culture have been exposed tofour continuous wind speeds for from 4 to 5 days. The plantswere exposed to natural daylight, humidity, and temperaturein a wind tunnel in which only air movement was controlled.The wind speeds found among the plants in the four sectionsof this tunnel were approximately 0·3, 0·7, 1·7,and 4·0 m./sec. The results showed no significant changein relative growth-rate or net assinilation rate with wind speed. Previously published results, obtained with plants in soil orsand culture, have differed from those in the present experimentsin showing a fall in the amount of growth as wind speed increased.It is suggested that the reduction in growth found in theseprevious experiments was caused by partial drying out of theplants, whilst in the present experiments water-supply to theroots was abundant and this effect was considerably reduced.     

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