MORPHOGENESIS OF THE STAMENLESS-2 MUTANT IN TOMATO. I. COMPARATIVE DESCRIPTION OF THE FLOWERS AND ONTOGENY OF STAMENS IN THE NORMAL AND MUTANT PLANTS

The single gene recessive mutant stamenless-2 (sl₂/sl₂) differs phenotypically from the normal (+/+) only in the stamen structure. Stamens of the mutant plants were laterally free, twisted, shorter, paler in color, possessed abnormal pollen, and bore naked external ovules (E.O.) on the adaxial surface near the junction of anther and filament. Mutant plants grown in the field during summer produced flowers in which a number of carpel-like organs (‘carpelloid stamens‘) with few or no E.O. replaced the stamens. On the other hand, plants grown in the greenhouse during winter possessed flowers with greater number of yellow and pubescent stamens and many E.O. Study of stamen ontogeny revealed that at initiation (up to 100 μ in length) stamen primordia of normal and mutant plants resembled each other. Thereafter the development of stamens in the two genotypes could be distinguished.     

A MORPHOGENETIC STUDY OF LANCEOLATE,A LEAF-SHAPE MUTANT IN THE TOMATO

Mathan , D. S., and J. A. Jenkins . (U. California, Berkeley.) A morphogenetic study of lanceolate, a leaf-shape mutant in the tomato . Amer. Jour. Bot. 49(5): 504–514. Illus. 1962.—The single-gene mutant, lanceolate (La/La⁺), which has simple, entire leaves rather than the oddpinnately compound leaves of the normal tomato (Lycopersicon esculentum), differs from normal (La⁺/La⁺) in many characters which can be related to fewer and larger cells in meristematic regions. The homozygous lanceolate (La/La) is sometimes lethal, but is usually expressed as reduced, which consists of a hypocotyl without cotyledons, or occasionally either by modified, in which there is a single fused cotyledon and a bud, or by narrow, in which the bud produces a shoot with simple leaves even smaller than those of lanceolate and a tendril-like inflorescence without flowers. In an attempt to overcome the effect produced by the lanceolate gene, the mutant was treated with a number of substances. Embryos without cotyledons cultured in White's medium plus adenine or tyrosine or both gave a higher frequency of narrow plants. With added gibberellic acid, no narrow plants developed from embryos without cotyledons. When tyrosine was sprayed on young narrow plants, they developed larger leaves and morphologically normal but sterile flowers. On the other hand, gibberellic acid sprayed on young lanceolate plants altered their development in the direction of narrow.     

FLOWER DEVELOPMENT IN NORMAL TOMATO AND A GIBBERELLIN-DEFICIENT (ga-2) MUTANT

Flower buds of a tomato (Lycopersicon esculentum Mill.) gibberellin-deficient mutant (ga-2/ga-2) were initiated, but did not develop to maturity and eventually aborted. If GA, was applied to a developing inflorescence or stem tip, completion of flower bud development and fruit set occurred. In development of the ga-2 flowers, the corolla and stamens did not elongate and the style was misshapen or extended past the tip of the anthers. Light microscope observations indicated that meiosis of both microsporocytes and megasporocytes did not occur. Cells of the sporogenous layer were initiated, but growth was arrested and they eventually degenerated. The ovary was normal in appearance. However, the megasporocytes degenerated, giving rise to a cavity in the ovule. Thus, although GA is not required for flower initiation in tomato, it is essential for meiosis of the microsporocytes and megasporocytes and elongation of the corolla and stamens.     

A COMPARATIVE STUDY OF PERMEABILITY IN PLANTS

Quantitative studies on Laminaria (a brown alga), Ulva (a green alga), Rhodymenia (a red alga), and Zostera (a flowering plant) show that the behavior of these plants, in respect to changes in permeability, is essentially alike in all cases.     

THE EFFECTS OF VARIOUS SUBSTANCES ON THE COMPARATIVE GROWTH OF EXCISED TOMATO ROOTS OF CLONES CARRYING DWARF AND NORMAL ALLELES

Lee , Addison E. (U. Texas, Austin.) The effects of various substances on the comparative growth of excised tomato roots of clones carrying dwarf and normal alleles. Amer. Jour. Bot. 46(1) : 16-21. Illus. 1959.—Excised tomato roots carrying the wd gene for dwarfness and its comparable normal allele, wd+, were cultured under various conditions in an effort to provide information as to the physiological differences between the 2 root clones. Two percent is the optimal sucrose concentration for both roots, although wd roots appear to be relatively more tolerant to high sucrose concentration than wd+ roots. The addition of yeast extract, casein hydrolysate, 1, 3-diphenylurea, and a combination of the last 2 in standard medium fail to improve growth of either wd or wd+ roots. The growth of wd roots is favored by the dark while that of wd+ roots is favored by the light. The addition of IAA to the medium fails to stimulate either type. The effects of eosin added to the medium in various concentrations were studied. High concentrations were inhibitory, but the effect of a concentration of 10^-9 g./ml. provided some evidence of an auxin differential between the two clones of roots. The effects of antiauxins were also investigated, but all of those used reduced the growth of both wd and wd+ roots. It was concluded that although there may be some differences in the auxin metabolism between wd and wd+ roots, it is not likely that this is the cause of dwarfism in the wd roots. Kinetin was found to stimulate both wd and wd+ roots in a concentration of 1.0γ/l. but the stimulation was not differential. Gibberellic acid was found to inhibit both wd and wd+ roots in relatively high concentrations. It had little effect on wd roots in relatively low concentrations, but was inhibitory to wd+ roots even in very low concentrations. Thus these substances appear not to be the cause of the dwarf condition of the wd roots.     

DEVELOPMENTAL BIOLOGY AND THE STUDY OF MALFORMATIONS

1. The scientific approach to malformations began with experimental work on abnormal conditions of incubation in the chick. 2. More precise experiments on causing abnormalities had a common origin with experimental embryology. 3. Progress in experimental teratology during the last fifty years is reviewed in a commentary on the four principles formulated by Stockard in 1921. 4. Some relationships are traced between the results of cytogenetical studies in man and in other organisms. 5. An account is given of present knowledge concerning malformations of the neural tube originating either experimentally, spontaneously, or phenotypically. 6. The teratological implications of some recent theories on the expression of the genotype are discussed, particularly in relation to problems of hormones as teratogens. 7. Some account is given of the implication of carbohydrate metabolism and terato-genesis. 8. Teratogenesis is possibly related to cationic balance in early development. 9. It is suggested that one factor retarding progress in the understanding of malformations is the tendency towards the development of teratology in an insufficiently close relationship with other branches of cell biology.     

COMPARATIVE BIOCHEMICAL STUDY OF TWO ALLELIC FORMS OF A GENE AFFECTING LEAF-SHAPE IN THE TOMATO

Through successive selfing of lanceolate, a leaf-shape mutant in the tomato, the 3 leaf-shape forms, namely, normal (La⁺/La⁺), lanceolate (La⁺/La), and homozygous lanceolate (La/La), were obtained in a uniform genetic background. The mutant allele lanceolate causes the increase in activities of the following oxidative enzymes: tyrosinase, laccase, peroxidase and catalase. The lanceolate gene exhibits a dosage effect with respect to these enzymes; the homozygous lanceolate shows the highest activity, heterozygous lanceolate is intermediate, and normal shows the lowest activity. The relative differences in activity of these enzymes between the 3 genotypes persist at all stages of development and in all organs examined.     

Morphogenesis of the Stamenless-2 Mutant in Tomato: III. RELATIVE LEVELS OF GIBBERELLINS IN THE NORMAL AND MUTANT PLANTS

Tomato plants of a single-gene recessive mutant, stamenless-2(sl₂/sl₂), bear abnormal stamens but produce near-normal flowersfollowing application of gibberellic acid. Data presented hereshow that mutant plants have lower levels of extractable gibberellin-likesubstances in vegetative as well as floral parts compared withnormal ones. The significance of these observations in relationto gene-controlled stamen form, and sexuality of plants is discussed.     

A COMPARATIVE STUDY OF THE OLFACTORY SENSITIVITY OF HUMANS AND RATS

Olfactory sensitivity of humans and rats to n-propanol, n-heptanol,benzaldehyde, isobutyln-butyrate, cyclohexanone and 1,4-dioxane(rats only), was determined. Similar results were obtained forboth species, and these compare favourably with those of otherworkers. Since the sensitivities of humans and rats varied fordifferent odorants in a similar manner, it is postulated thatthe mechanisms for detecting odors may be common to many vertebrates.It is proposed, in agreement with Adrian (1956), and Moultonet al. (1960), that the relative area of the olfactory epitheliumdoes not necessarily determine the sensitivity of an animal. ^*This paper reports research undertaken at the School of BiologicalSciences, Macquarie University, North Ryde, N.S.W., 2113, Australia,and the CSIRO Division of Food Research.     

INFLUENCE OF LIPIDS ON THE ACTIVITY OF CEREBROSIDE-SULPHOTRANSFERASE IN MOUSE BRAIN: A COMPARATIVE STUDY OF JIMPY AND NORMAL MOUSE BRAINS 1

Abstract— The effect of lipids other than the substrate cerebroside on the activity of cerebroside-sulphotransferase (CST) in Jimpy and normal mouse brain was investigated. The enzyme activity of an acetone-treated microsomal preparation can be stimulated in the presence of the extracted lipids either with or without addition of exogenous cerebroside as a substrate. The CST activity in the Jimpy mutant compared to that in normal animals differs from 18% in homogenate to approx 80% in solubilized or acetone-extracted microsomes. An addition of total lipid from normal mouse brain to microsomal preparations from which lipid has been removed by acetone results in a stimulation of Jimpy CST activity up to a value of 80% of normal mouse brain microsomes. Both Jimpy and normal mouse brain CST can be also stimulated by the addition of single lipid components such as cholesterol and lecithin by 50% in normal and 100% in Jimpy brain microsomes. These findings lead to the hypothesis that there is a lipid requirement for CST activity other than the substrate cerebroside.     

THE COMPARATIVE AND DEVELOPMENTAL MORPHOLOGY OF THE ROOT SYSTEM OF SELAGINELLA SELAGINOIDES (L.) LINK

All of the roots of Selaginella selaginoides are attached laterally to the base of the shoot, which has monopolar growth as is characteristic of Selaginella. The first three roots are produced by meristematic activity in the cortex of the hypocotyl as in several other species of Selaginella. The fourth root is produced in the same way as the first three, except that not all of the cortical cells which become meristematic mature into root tissue. Some of the meristematic tissue remains undifferentiated and continues to produce additional roots. Potentially an unlimited number of roots could be produced, but no plant was found to have more than eight. There is some secondary growth in the cortex of the basal swelling on the hypocotyl, but no secondary vascular tissue is produced and no cambium of any sort is ever organized. On the basis of comparisons with other living species of Selaginella. the centralized root system of S. selaginoides is interpreted as having been modified from a noncentralized type of root system by the persistence of the juvenile mode of root production.