Showing papers on "Endosperm published in 1970"

Dependence of the r-mottled aleurone phenotype in maize on mode of sexual transmission

Abstract: YPICAL R-mottling, the irregular distribution of anthocyanin in the aleurone Tlayer of maize endosperm, occurs upon crossing appropriate R R plants with r r (colorless) only when R R is the pollen parent (EMERSON 1918; KEMPTON 1919). When R R is used in the mating as female, the aleurone is solidly colored. From a conventional point of view the mottled and solidly colored phenotypes suggest the dosage effects associated with the unequal numbers of chromosome sets contributed to the triploid endosperm, two from the female and one from the male parent. This explapation assumes equal pigmenting action of R from the two origins. Furthermore, if parental source were to affect R expression, such an influence ordinarily would be confounded with the effect of dosage. ROMAN’S (1947) discovery that a given chromosome segment translocated to the centromeric portion of an accessory B chromosome in maize is transmitted by the male in duplicate provides an opportunity to vary the dosage of genes in such a segment independently of parental origin. Accordingly, his translocation B-loa, with the point of interchange in chromosome-10 between R and the centromere, permits introduction of two R factors into the endosperm via pollen. Unexpectedly on the R dosage interpretation, R R from the male when combined with rr from the female gave mottled, rather than solidly colored, kernels (ROMAN, cited by SCHWARTZ 1965; KERMICLE 1963). This observation called into question sufficiency of the dosage explanation and prompted further investigation. The evidence presented here shows the basis of the disparity in aleurone phenotype following reciprocal crosses between R R and r r plants is a pronounced difference in level of action at which R is transmitted to the endosperm through male and female gametophytes. MATERIALS AND METHODS The various alleles of R involved affect anthocyanin pigmentation of the aleurone and vegetative parts of the plant as follows: RV-Pigmented aleurone, red seedling and anthers; representative of those alleles which give darkly mottled aleurone in crosses to rgrg as female but solidly colored aleurone when rgrg is male. The particular Rr employed in experiments involving translocation B-loa was that present in the TB-loa stock obtained from the Maize Genetics Stock Center, University of Illinois, Urbana. A second source of Rr, that designated standard Rr in the Wisconsin collection, was 1Paper No. 1357 from the Laboratory of Genetics. Supported by AEC contract AT(ll-1)-1300 and NIH grant GM 15422-01.

Cytochemical and developmental changes in microbodies (glyoxysomes) and related organelles of castor bean endosperm

Abstract: Structural changes in endosperm cells of germinating castor beans were examined and complemented with a cytochemical analysis of staining with diaminobenzidine (DAB). Deposition of oxidized DAB occurred only in microbodies due to the presence of catalase, and in cell walls associated with peroxidase activity. Seedling development paralleled the disappearance of spherosomes (lipid bodies) and matrix of aleurone grains in endosperm cells. 6 to 7 days after germination, a cross-section through the endosperm contained cells in all stages of development and senescence beginning at the seed coat and progressing inward to the cotyledons. Part of this aging process involved vacuole formation by fusion of aleurone grain membranes. This coincided with an increase in microbodies (glyoxsomes), mitochondria, plastids with an elaborate tubular network, and the formation of a new protein body referred to as a dilated cisterna, which is structurally and biochemically distinct from microbodies although both apparently develop from rough endoplasmic reticulum (ER). In vacuolate cells microbodies are the most numerous organelle and are intimately associated with spherosomes and dilated cisternae. This phenomenon is discussed in relation to the biochemical activities of these organelles. Turnover of microbodies involves sequestration into autophagic vacuoles as intact organelles which still retain catalase activity. Crystalloids present in microbodies develop by condensation of matrix protein and are the principal site of catalase formerly in the matrix.

The early stages of grain development in wheat: response to light and temperature in a single variety.

Abstract: For wheat plants (cv. Gabo) grown under natural daylight at a temperature of 21/16°C, increase in dry weight of the stem exceeded that of the ear for the first 10 days following anthesis. Higher temperatures (27/22°C) resulted in a greater rate of grain development, with a corresponding increase in the rate of cell division in the endosperm tissue, and a shortening of the stem growth period. Despite initial differences in the rates of cell division with variation in temperature, the final number of cells formed in an endosperm did not vary significantly between temperature treatments. Dry weight accumulation in the stem was, in contrast to the grain, highest at lower temperatures (15/10°C).

Nature of proteins in triticale and its parental species: i. solubility characteristics and amino acid composition of endosperm proteins

Abstract: Solubility characteristics and amino acid composition of the endosperm proteins of one line of Triticale, its durum wheat and rye parent cultivars, and one cultivar of hard red spring wheat were co...

Developmental studies on glyoxysomes in ricinus endosperm

Abstract: The development of glyoxysomes and their associated enzymes, isocitrate lyase and malate synthetase, was studied in the endosperm of castor bean seeds during germination and early growth in darkness. The protein content of the glyoxysome fraction, separated by sucrose density centrifugation, increased linearly from day 2 to day 4 and declined subsequently, while maximum enzyme activities were reached at day 5. The specific activities of the enzymes in the glyoxysomes increased until day 5 and remained constant thereafter. At all stages of germination the only organelle with isocitrate lyase activity was the glyoxysome, but at the earlier stages a greater portion of the total activity was recovered in the soluble form. Malate synthetase was found primarily in the glyoxysomes after day 4, but at earlier stages part of the activity appeared at regions of lower density on the sucrose gradient. It was shown that this particulate malate synthetase activity was due to glyoxysomes broken during preparation, and that, as a result of this breakage, isocitrate lyase was solubilized. We conclude that both enzymes are housed in the glyoxysome in vivo throughout the germination period, and that the rise and fall in enzyme activities in phase with fat breakdown correspond to the net production and destruction of this organelle.

Origin and development of protein granules in maize endosperm

Abstract: Protein granule development in the starchy endosperm of normal maize (inbred line, W46A) was studied with optical and electron microscopy. The granules were first observed 12 days after pollination as spherical deposits, usually single, within an enclosing membrane. They developed from vesicles produced by the endoplasmic reticulum and were formed both as small localized cisternal dilations and as enlargements at the ends of endoplasmic reticulum. Dictyosomes also appear to proliferate protein granule vesicles. The protein accumulated in the granules appears to be synthesized outside the membranes. Once initiated, the granules rapidly increase in size and number as the kernel develops; their final diameter ranges up to 2 IA. Immature granules stain with a variety of biological dyes in aqueous solution as well as with metal stains; mature granules stain lightly or not at all. At kernel maturity, the protein granules are embedded in a protein

Distribution of tocopherols within the corn kernel

Abstract: The concentration of tocols and tocotrienols in the germ, endosperm and pericarp of the corn kernel was determined after hand dissection of four dent corn hybrids—normal, early maturing, high oil and high lysine (opaque-2). Among these hybrids the germ fraction contained 70–86% and the endosperm fraction contained 27–115 of the tocopherols extracted from the whole grain. The endosperm fractions contain all of the measurable tocotrienols occurring in whole corn. In the four hybrids analyzed, the germ fraction contained 94–96% of thea-tocopherol extracted from the whole grain. Concentration ofa-tocopherol was the highest in the germ fraction of the opaque-2 hybrid.

The role of phytic Acid in the wheat grain.

Abstract: The concentrations of adenosine triphosphate and phytic acid in testa, embryo plus scutellum, aleurone, and endosperm fractions from grain of Triticum vulgare cv. Insignia have been determined during development under both normal conditions and those of water stress. Phytic acid was not detected in the endosperm. In the embryo plus scutellum and aleurone fractions there was a rapid build-up of phytic acid, but the adenosine triphosphate level did not change markedly at this time. These results are not consistent with physiological roles previously suggested for phytic acid other than the role of phytin as a phosphorus and cation store for the germinating seed.

Cytokinin activity in avocado seeds during fruit development.

Abstract: The soybean callus bioassay was used to determine levels of cytokinin activity in avocado (Persea americana) seeds.In the embryo, levels are high during the early stages of development, but diminish as the fruit grows. The level of cytokinin activity in the endosperm is very high throughout the period that this tissue exists. The seed coats have very high activity levels while the fruit is young, reaching values comparable with those found in the endosperm. The activity level falls as the rate of fruit growth slows down and disappears completely by the time the seed coats shrivel at approximately the same time the fruit reaches "horticultural maturity".

Lipid and morphological changes in developing rapeseed, Brassica napus.

Abstract: Self-pollinated seed from normal and erucic acid free plants of summer rapeseed (Brassica napus L.) was harvested at weekly intervals from pollination to maturity. Oven-dried whole seeds and their component parts were weighed and analyzed for oil content and fatty acid composition. Oil and dry matter accumulation followed sigmoidal patterns, most of the deposition occurring between 14 and 35 days after pollination (DAP). The relative contribution of the testa, endosperm and embryo to dry weight and oil content of whole seeds changed significantly during seed development. Oil content of the developing embryo varied from 22 to 44%, and the testa from 1.6 to 13%, although at maturity only 6 to 8% oil was found in the testa and adhering aleurone. The nucleate endosperm oil content was estimated to be low and in the order of 2 to 2.5%. In 7- to 14-day-old seeds the dry weight, oil content and fatty acid composition were largely determined by the testa and endosperm. From 14 to 21 DAP the testa and embryo were ...

Energetics of Early Seedling Growth in Corn (Zea mays L.)1

Abstract: The purpose of this report is to explain some of these Early growth of the com seedling was studied in relaenergy relationships involved in the germinating seed. tion to its dependence on energy from endosperm and early photosynthetic tissue. ~easurc:ments ,..ere made of EXPERIMENTAL PROCEDURE (1) endosperm utilization rate of seedlings grown in light and dark; (2) growth and leaf area of seedlings as affectEndosperm Utilization and Growth of Com ed by partial endosperm removal; and (J) photosynthesis (P), respiration (R), and .':CO, up~ake of seedlings as Hybrid field com seed was selected because of its large size. affected by endosperm eXCISion at different ages. Endo'Ve determined endosperm utilization and growth of corn seedsperm utilization and growth rates were similar in l~ght lings in the light and in the dark in t\\-O experiments. In the and dark unt.il the two.leaf stage 10 days after germmafirst experiment, 28 \..eighed lots of 10 seeds each were germintion. Regression of root and shoot growth on age was ated in the light and 28 similar lots in the dark. Seedlings were 15.4 mg/day and of root and sh~t growth on endosperm grown on plexiglass slant boards covered \vith \vet blotter paper. ,,-eight loss was .65 mg/mg. Partial removal of the endoSeeds from each lot \vere placed in a line 7.6 cm from the top sperm at seeding resulted in decreased growth of roots of the board and held in place by wetted tissue paper. The and shoots and indecreased leaf area per seedling. Apseeds ,vere then covered "ith blotter paper, \vhich remained parent P was uegati~'e at 9 days of age and was greatest \"et from \"ater mo\ing up the boards from trays set at their for seedlings "ith endosperm excised. Apparent P was bases, The plants \"ere grown in a growth chamber with a positive and similar at days 11, 12, and 13 for seedlings temperature of 21,8 :t: 1 C. a light intensity of 20,000 lux and "ith endosperm e.xcised and was positive, and increased a photoperiod of 15 hours. For the dark treatment. slant boards from day 11 to day 13 for seedlings with endosperm. ,vere covered with a large cardboard box. Temperature within Energy obtained from CO, fixation was not equivalent the box was assumed to be equal to that of the growth chamber. to that supplied by the endosperm until the lOth day. At Two seed lots ,vere sampled from both light and dark treat. this time seedlings had two fully emerged leaves. Absorpments during a 22-day period at 2-day intervals from germination of 1'CO, ',-as similar for seedlings \vith and without tion. At each sampling date, seedlings ,vere separated into endospetm, and increased ,,'ith age as a result of increased roots, shoots, endosperm, and scutellum. These components leaf area and increasl'{l absorption per unit of leaf area. \vere placed into ,veighing bottles, oven-dried. and weighed. Endosperm removal resulted in greater translocation of The second study \vas similar to the first, except that sam. 1'CO. to seedling roots. plillg \vas at I-day intervals from the 5th throllgh the 16th day, . .. and the sclltellum ,''as weighed \vith the endosperm. Additional inde_'\: words: PhotosynthesIS, Respiration, Gennination energ,.. . Photosynthesis and Respiration Corn seedlings \..ere gro\vn on slant boards in the light under S OURCES of energy for early growth of a grass seedthe experimental conditions previously described. From the 8th ling are: first, the endosperm; second, the endoto the 12th day, the largest and most unifo,rm seedlings w.ere Sperm and ne" leaf material' and third new leaf mas~lected and paired for study of photosynthetic, (P) and resplra. . . , h tlon (R) rates. From one member of each pair the endosperm tenal after depletion of the endospe~n. T ese stages \vas excised \vith a razor blade. Each seedling was then placed of energy dependence have been denned by Whalley. in a 65-cc bottle half-filled with a complete nutrient solution, '~ McKell, and G;reen (6) as hete;otrophic, transitional, and ,vas hel~ in place by cotton wedged between t~e seedling " 'j, and autotro ph1c stages of seedl1ng develo p ment. The and the neck of the b?ttle. After 24 ~ours of seed~mg growth, . .' ch P and R of leaf matenal \vere determmed. Just prior to deterrol: of the en.dosperm 1.11 g~rm~natIon and the. anges minations, strips of bees,vax were wedged bet\veen the seedling whIch occur In the redIstnbut10n of metabol1tes have and th bottle neck, to seal off the top from the root environbeen thoroughly studied b)' other workers, particularly mel~t. T~us, CO, exchange determinations .\,-ere made on the I .n corn (2 3) Little is known however concerning top. only, bllt as affected by the absence or presence of endo1 .'.., " sperm. Measurements of P and R were made m a leaf chamber the relative contrIbutions of endosperm and ne,v leaf at 21.8 C, and 30% relative humidity. Light energy during P material to the total energy of the plant. ,vas 0,33 cal/cm'/min pro,ided by three 500-\vatt photo flood In P revious studies on the effect of tem p erature fila~ent !ight~. Measurements of P an.d dark R were made by . . . passmg air \Vlth a CO, content of 325 ppm through the leaf stress on seedling gro~.th, rate of endosperm utIl1zachamber and measuring the increase or decrease in CO. of air tion was used as a criterion in delineating the stage coming out of the leaf chamber with an infra-red gas analyzer. of seedling de,elopment. Green shoots developed 10llO' Flo\v of air through the chamber \vas controlled at rates of from bef?re the en~osper~ '''as completely. utilized (1, .4f ~r~e;t~iters per min, depending on the amount of leaf material ThIS observauon raIsed several questions concermng At each seedling age, P and R measurements were made on energy relationships. What is the importance of endothree to sLx replications of seedlings ,vith or \\ithout endosperm, I spenn once the green shoot has emerged? Is its rate of ~llm~ers ,of seed~ings 'per replication ,vere ,~ec.reased ~it? age t'l. t'o ffected by the Presence of the green shoot and size m order to keep air flow rates \'Ithm .the lImits of u 1 1Za 1 n.a .. . Ollr flo\\.meters, and ,vere 5. 3, 3, 2, and 1. respectively for ages and what IS the contrIbutIon of the latter to the seedof 9, 1°, 11, 12, and 13 days. Follo,ving each determination. ling while energy is still available from the endospenn? leaves \vere clipped at the surface of the \vax on each bottle. traced on paper, oven-dried. and ,veighed. Rolled or partially I rolled leaves \vere not unrolled for tracings of leaf area, Leaf 1 Contribution from theCrops Research Division, Agricultural tracings were cut out and \veighed. The ratio of area to ,veight Research Service, U. S. Department of ,\griculturc and the Monof paper ,..as llscd to calculate leaf areas. tana Agricultural Experiment S~ation. Publis~ed with approval , of the director as Paper No. 98:). Journal Series, Montana Agr. 14COZ Labellmg Exp. Sta. Received July II, 1969. . . . . , , :\gronomist, Crops Research DIvIsion: -,\~S, USDA and Seedlmgs of S, 9, .'°, II. and 12 days o~ age, \vlth and lVlthout gradllate assistant, Dept. of Botany and ;\Ilcroblology, Montana cndosperm. ,vere glv~n ~'C~. to det.ermme the effe~t of endoState University. Bozeman, ~Iont. 59715. sperm removal on distrIbution of fIXed CO.. Seedlmg growth

Cytokinin Content of Pea Seeds during their Growth and Development

Abstract: 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.

Studies on Seeds: V. Microbodies, Glyoxysomes, and Ricinosomes of Castor Bean Endosperm

Abstract: Glyoxysomes, a form of microbody, are present in castor bean endosperm during the first 8 days of seed germination. They have a "typical" microbody form and are shown histochemically to contain catalase. The catalase label is distributed throughout the microbody and is not an exclusive feature of the crystalline or amorphous core.Castor bean endosperm contain a second cytosome, only slightly larger than the glyoxysomes, which is bound by a rough-surfaced membrane and which does not label for catalase. We have not observed these cytosomes in other tissues, suggesting that they may have a specific cellular function characteristic of castor bean endosperm.

Distribution of fatty acids within the seed of flax

Abstract: Fatty acid analysis of oil from the basal, mid, and apical portions of individual flaxseeds (Linum usitatissimum L.) revealed that the portion nearest the embryo axis had more palmitic and linoleic acid and less oleic and linolenic acid than the remainder of the seed.Seed of flax selection F.P. 497 was dissected into three components, embryo axis, cotyledons, and combined testa and endosperm. The embryo axis tissue contributed only 4.4% of the total seed oil, but its fatty acid composition differed significantly from that of the attached cotyledons. The embryo axis contained 11.3% palmitic, 5.0% stearic, 10.6% oleic, 28.1% linoleic and 45.0% linolenic acid compared with 5.1, 4.7, 17.6, 14.0 and 58.6%, respectively, for the cotyledons.The testa and endosperm contained 21.6% of the total oil and had a high level of palmitic but a very low level of stearic acid. These two tissues significantly influence overall seed composition; therefore they must be considered in microsampling.

Relationship Between Levels of Soluble Carbohydrate and Starch Synthesis in Detached Ears of Wheat

Abstract: Detached ears of wheat were cultured on solutions of sugars. 'A highly significant correlation was observed between the concentration of sucrose in the endosperm and the rate of starch synthesis. Fluctuations in the level of sucrose in the endosperm were accomp!1nied by parallel changes in the rate of starch synthesis. It is suggested that the concentration of sucrose in the endosperm regulates the rate of starch synthesis.

α-amylase-isozymes in gibberellic-acid-treated barley half seeds.

Abstract: The presence of multiple forms of α-amylase in gibberellic acid-treated embryoless barley half-seeds was demonstrated by separation on diethylaminoethyl-Sephadex and isoelectric focusing polyacrylamide gel disc electrophoresis. Two major α-amylase fractions (A and B), each consisting of two to three isozyme components, were purified. α-Amylase fractions A and B were distinguishable in their reaction patterns. The optimal pH of fraction A α-amylase was found to reside in the acidic side (pH 5.0), as was determined by analyzing the reducing sugars formed as well as the paper chromatographic detection of reaction products. At neutral pH, 6.9, fraction A exhibited weak amylolytic activity in forming maltose. The α-amylase activity in fraction A was markedly stimulated by heat treatment (70 C/15 minutes). Fraction B, constituting a major part of amylases in the endosperm extract, was also found to be composed of α-amylase, as evidenced by the loss of enzyme activity upon allowing fractions A and B to stand at pH 3.3 for a prolonged period. The possible physiological function of the two different types of α-amylase in the carbohydrate breakdown of barley seeds is discussed.

Ageing in Triticum durum Seeds: Behaviour of Embryos and Endosperms from Aged Seeds as Revealed by the Embryo-transplantation Technique

Abstract: The embryo-transplantation technique has been used to study the behaviour of Triticum embryos and endosperm during the course of ageing of 1-, 2-, 3-, 4-, and 5-year-old seeds. The results show that the ageing process in Triticum seeds is a progressive phenomenon. It affects both embryo and endosperm as shown by (a) the behaviour of old embryos transplanted on young endosperms, and (b) the deleterious effects of aged endosperms on young embryos.

Fatty acid biosynthesis and incorporation into lipid classes in seeds and seed tissues of flax

Abstract: Fatty acid metabolism in developing flaxseeds was studied by incubating whole seeds or isolated seed tissues in buffered solutions of 1-14C-acetate, 2-14C-malonate and14CO2. Lipid classes were separated by thin layer chromatography, and fatty acid labeling in phospholipids, diglycerides and triglycerides was determined by combined thin layer and gas liquid chromatographic techniques. Incorporation of14C from acetate into embryo lipids was very rapid with phospholipids and 1,2-diglycerides becoming highly labeled in treatment times as short as 5 min. Triglycerides were labeled more slowly. Phospholipid radioactivity was largely associated with the phosphatidyl choline fraction. Oleic acid had the highest specific activity of all major fatty acids in short treatment periods. This was followed in decreasing order of activity by palmitic, linoleic, stearic and linolenic acids. As the treatment period was lengthened to 90 min or longer, linoleic and linolenic activities were markedly increased. Use of malonate or CO2 rather than acetate as the substrate increased the labeling of the saturated acids. Incorporation of14C from acetate into lipids of endosperm tissues and whole flax seeds was slower than incorporation into embryo lipids. Stearate had the highest specific activity of the fatty acids in endosperm and whole seeds.

Ribonuclease Activity in Normal, opaque-2, and floury-2 Maize Endosperm during Development

Abstract: The elevated ribonuclease activity produced in the endosperm of a maize (Zea mays L.) inbred, W64A, by homozygous opaque-2, results from a more than doubled rate of ribonuclease accumulation occurring prior to 16 days post-pollination; after 16 days the rates in opaque-2 and normal are the same, suggesting that opaque-2 is no longer active. The pattern of ribonuclease increase in the opaque-2 dosage series indicates that opaque-2 is not fully recessive. Ribonuclease accumulation is not affected by floury-2 in a second inbred, B14. The results are discussed with reference to other proteins, notably zein, the net synthesis of which is affected by opaque-2.

A Lethal Toxic Substance for Brewing Yeast in Wheat and Barley

Abstract: It is shown that among various grains, wheat and barley contain in the endosperm a toxic substance to brewing yeast, and the substance is easily extracted with a dilute sulfuric acid solution. One unit of the toxicity is defined as the lowest amount of the extract which inhibits the yeast growth in 10 ml of wort medium. Two or more units of the toxicity not only inhibited the yeast growth, but also caused the death of yeast cells. Although the toxic effect was not observed when divalent metallic ions such as Ca2+, Zn2+ or Fe2+ were present at a concentration of 5 × l0−3 mole or more, the toxicity could be recovered by the addition of ethylene-diamine-tetra-acetate (EDTA). Genetic relationships on the content of the toxicity in wheat and barley and sensitivity of yeast strains to the toxicity are also presented.

Ovule development in seeded and seedless grapes

Abstract: Female gametophyte and early embryo and endosperm development were examined in 3 seedless grape varieties, Himrod, Interlaken Seedless and N. Y. 15302, and in their seeded parent Ontario. A high proportion of functional embryo sacs was found at full bloom in all varieties. Fertilization occurred in all varieties. Precocious initiation of endosperm was observed with Himrod and extremely rapid development of endosperm was found with N. Y. 15302. Early degeneration of zygotes, failure of the zygotes to divide, and endosperm degeneration were observed in the seedless varieties with smallest seed remnants, Himrod and Interlaken Seedless. Imperfect development of the zygote and endosperm resulted in seed abortion (stenospermy) and seedless fruit (stenospermocarpy) in Himrod and Interlaken Seedless varieties.

Response of cereal grains to gibberellic acid

Abstract: Aleurone cells of oats produce significantly less α-amylase than the aleurone cells of rye, wheat or barley after treatment with gibberellic acid (GA3). Furthermore, excised embryos from oats, rye, wheat or barley are more efficient than exogenous gibberellic acid in catalysing the production of α-amylase in oats endosperms. Enzymic modification of the endosperm of oats, as distinct from the other cereal grains, is associated with rapid elongation of the scutellar apex under the aleurone cells.

Abnormalities of endosperm development in Lilium hybrids.

Abstract: Of 191 interspecific crosses attempted between 27 different species representing different subgenera ofLilium only 14 gave rise to seeds and only 6 of these were viable. Sterility was associated with various types of abnormality in endosperm development. Many of these irregularities involved chromosome breakage and reunion but others entailed abnormal DNA replication and chromosome coiling. In one cross the individual endosperm nuclei contained four stranded structures, the behaviour of which at division was similar to that of bivalents at meiosis. The embryo-sac ofLilium is of theFritillaria type, containing both haploid and triploid polar nuclei. As a consequence the balance between the number of chromosome sets in the embryo, endosperm and maternal tissue is 2:5:2 and not 2:3:2 as is more commonly found in diploid species. It is suggested that sterility results from genetic imbalance of the endosperm itself rather than interaction of the endosperm with either embryo or maternal tissue.