THE DEVELOPMENT OF THE SEED OF ABUTILON THEOPHRASTI. II. SEED COAT

Winter , Dorothy M. (Iowa State U., Ames.) The development of the seed of Abutilon theophrasti. II. Seat coat. Amer. Jour. Bot. 47(3) : 157—162. Illus. 1960.–The integuments of Abutilon theophrasti Medic. undergo a rapid increase in size, predominantly by anticlinal cell divisions during the first 3 days after fertilization. Within 7 days, the outer epidermis of the inner integument becomes thick walled. At maturity this compact, lignified, and cutinized palisade layer accounts for more than half the thickness of the seed coat. During early growth, the palisade cells form a continuous layer in the micropylar region. In the chalazal region the palisade layer is discontinuous in a slit-shaped region, 60 × 740 microns. The shape of this discontinuity constitutes a major difference between dormant-seeded Abutilon and non-dormant Gossypium seeds. Exterior to the palisade layer is the outer integument which consists of a small-celled layer and a large-celled layer sparsely covered with unicellular, lignified hairs. Interior to the palisade is the thick mesophyll of the inner integument which is largely digested during seed growth and leaves only 2 pigmented cell layers in most regions at maturity. The inner epidermis is small-celled, pigmented and cutinized and adheres tightly to the endosperm. Seed coat impermeability increases with seed maturity. Even immature seeds will germinate, if scarified, indicating a lack of embryo dormancy.     

INFLORESCENCE AND FLOWER DEVELOPMENT IN THE PIPERACEAE. II. INFLORESCENCE DEVELOPMENT OF PIPER

The inflorescence development of three species of Piper (P. aduncum, P. amalago, and P. marginatum), representing Sections Artanthe and Ottonia, was studied. The spicate inflorescences contain hundreds or even thousands of flowers, depending on the species. Each flower has a tricarpellate syncarpous gynoecium and 4 to 6 free stamens, in the species studied. No sepals or petals are present. In P. marginatum the apical meristem of the inflorescence is zonate in configuration and is unusually elongate: up to 1,170 μm high and up to 480 μm wide during the most active period of organogenesis. Toward the time of apical cessation both height and diameter gradually diminish, leaving an apical residuum which may become an attenuate spine or may be cut off by an abscission zone just below the meristem. The active apex produces bract primordia; when each is 40–55 μm high, a floral apex is initiated in its axil. Both bract and floral apex are initiated by periclinal divisions in cells of the subsurface layer. The bracts undergo differentiation rather early, while the floral apices are still developing. The last-produced bracts near the tip of the inflorescence tend to be sterile.     

ONTOGENY OF CHICKEN HEMOGLOBIN II. CHROMATOGRAPHIC STUDY OF THE HETEROGENEITY OF HEMOGLOBIN IN DEVELOPMENT

Some properties of the carbonmonoxyhemoglobin (HbCO) from chicken embryos of ages 5, 10 and 15 days of incubation, from 1-day posthatching and from adult chickens have been investigated by chromatography on carboxymethylcellulose (CM-cellulose) column and by starch gel electrophoresis.
Chromatogram of the hemoglobin (Hb) from 5-day chicken embryos has shown that it consists of at least 6 components. Starch gel electrophoresis of each isolated component from the column in phosphate (pH 6.8), in borate (pH 8.6) and in formate buffer (pH 1.9) has shown later that there are 3–4 embryonic type Hb components in 5-day embryos.
Chromatogram of the hemoglobin from adult chickens has shown that it consists of at least 4 components, but the examination of each isolated component from the column by electrophoresis in phosphate (pH 6.8), in borate (pH 8.6) and in formate buffer (pH 1.9) has shown that there are 4–6 adult type Hb components in adults.
In ontogenic process, embryonic Hb type is detectable in embryos up to 15 days of incubation. Fetal Hb type, which is not detectable in adult chickens, can be first found in 10-day embryos.     

CHARACTERIZATION OF DEVELOPMENT IN MAIZE THROUGH THE USE OF MUTANTS. II. THE ABNORMAL GROWTH CONDITIONED BY THE KNOTTED MUTANT

The maize mutant Knotted (Kn) is characterized by hollow, finger-like outgrowths (knots) occurring mainly in the leaf blade. Portions of the ligule are displaced from the normal position to more distal locations within the blade. Knots apparently result from continued meristematic activity of isolated patches of cells surrounded by maturing tissue. Small knots appear to be centers of cell division. Epidermal cells overlying a small knot have been observed to undergo periclinal divisions. In addition to cell division, a reorientation of the axis of cell elongation is associated with knot formation. The pattern of knot distribution varies at different levels on the plant axis and within a leaf blade. From leaf 4 to leaf 10 or 11 the number of knots per leaf increases progressively, then declines in leaves initiated later. Knots always occur in association with lateral veins. The greatest number per vein occurs on the 3rd or 4th vein from the midrib. One plant developing from an X-rayed heterozygous seed possessed a sector of normal tissue bisecting the plant in a vertical plane passing through the midrib of each leaf except the top two. The normal sector was knot-free and had the ligule restored to the normal position. These observations suggest that cells with the characteristics of those from intercalary meristems occur throughout the blade in Knotted plants.     

CULTURE CONDITIONS AND THE DEVELOPMENT OF THE PHOTOSYNTHETIC MECHANISM : II. AN APPARATUS FOR THE CONTINUOUS CULTURE OF CHLORELLA

1. An apparatus has been developed which maintains a constant density of population of Chlorella by automatic dilution of the growing culture with fresh medium. 2. Cells harvested from the apparatus in daily samples are highly uniform in rate of growth and rate of photosynthesis measured under arbitrarily chosen conditions.     

Growth and Development in the Young Tomato: II. THE EFFECT OF DEFOLIATION ON THE DEVELOPMENT OF THE SHOOT APEX

In tomato seedlings the effects of high temperature in delayingthe enlargement of the shoot apex and of increasing the numberof leaves produced before flowering, were counteracted by removalof the first two leaves during the early vegetative phase. Inplants grown at 25° C. defoliation was followed by rapidenlargement of the apex and earlier flower initiation, the numberof leaves produced before flowering being reduced to that inplants grown at 15° C. Defoliation of plants grown at 15°C. resulted in only a slight increase in the rate of apicalenlargement, and the time to flowering and number of leaveswere unaffected. Growth analysis showed that at the time ofremoval, the first two leaves were not self-supporting and at25° C. were utilizing a much higher proportion of assimilatetranslocated from the cotyledons than at 15° C. These resultsare considered to support the view that at higher temperatures,the first two leaves compete strongly with the shoot apex forsupplies of assimilate.     

GROWTH AND DEVELOPMENT OF THE MYXOMYCETE PERICHAENA VERMICULARIS. II. CHROMOSOME NUMBERS AND NUCLEAR CYCLES

Chromosome counts of dividing nuclei of the myxomycete Perichaena vermicularis indicate a number of 25 ± 2 in the amoebae and 50 ± 4 in the Plasmodia, confirming earlier reports that amoebae are haploid and plasmodia diploid. Chromosome numbers obtained from nuclei during sporangial development indicate a fluctuation in the location of meiosis influenced by environmental conditions. The implications of these observations are discussed in reference to past conflicting evidence of the location of meiosis.