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Studies with Eudorina elegansL. were done to provide additional information on the effect of phenyl urea herbicides on phytoplankton. Colonies were grown in various concentrations of DCMU, 3(3,4‐dichlorophenyl)‐1,1‐dimethylurea. DCMU at 10‐5m induced an algicidic response. DCMU at 10‐7M and 10‐9M caused a significant reduction in the growth of colonies. Photosynthesis was significantly inhibited at all concentrations of DCMU. A rapidly growing population of algae treated with 10‐7m and 10‐9m DCMU showed a reduced motile/non‐motile balance of colonies.

Vegetative seedlings of the Ceres strain Brassica campestrisL., a quantitative, long‐day plant, were induced to flower by exposure to a 16‐hr, long‐day cycle. Cytohistological and cytohistochemical changes associated with inflorescence development were examined. Developing shoot apices were classified in vegetative, transitional, and reproductive stages. The vegetative apex possessed a biseriate tunica, central zone, peripheral zone and pith‐rib meristem. The transitional stage at 48 hr was marked by an increase in size and by a stratification of the upper cell layers of the shoot apex with a concurrent decrease of apical cytohistochemical zonation. The reproductive stage was initiated at 58 hr by periclinal cell divisions in the 3rd and 4th cell layers of the flank region. Cytohistochemical zonation in the vegetative apical meristem was restored in the floral apex. An “intermediate developmental” phase was not observed between the vegetative and reproductive stage.

This study uses SEM and LM to investigate the ontogeny and histogenesis of the tassel and ear spikes, spikelets and florets of diploperennial teosinte, Zea diploperennislitis, Doebley, and Guzman. The pattern of development observed in this teosinte is compared to the literature descriptions of corresponding development in Zea maysL. The data indicate two distinct developmental patterns in teosinte: one characteristic of the male and mixed inflorescences; the other the female inflorescence. The branching pattern we observed in male and mixed inflorescences of diploperennial teosinte is identical to that described in both the male and female inflorescences of Z. mays.The initial primordium, a bract produced along the primary axis, subtends an axillary branch which bifurcates unequally, forming two spikelets, pedicellate and sessile. The sessile spikelet is interpreted as a branch of the pedicellate spikelet. The first bract produced on each spikelet is the outer glume. The developmental pattern of a mixed inflorescence shows a transition from distichous four‐rowed staminate spikelets to distichous two‐rowed cupulate fruitcases. At the transition node, a staminate pedicellate spikelet and a pistillate sessile spikelet is observed. In the pistillate spikelet, the outer glume becomes part of the cupulate fruitcase. In the female inflorescence, only a single spikelet forms in the axil of the initial primordium: the axillary branch primordium becomes the spikelet apex; and the initial primordium becomes the outer glume, eventually a part of the cupulate fruitcase. The first bract produced by the spikelet apical meristem is the inner glume. There is only one observable spikelet and no recognizable rudimentary spikelet, pedicellate or sessile. Therefore, while the cupulate fruitcases of female and mixed inflorescences appear identical at maturity, they do not have the same ontogeny. The evidence supports a hypothesis that the progenitor of a Z. maysear may be a mixed teosinte inflorescence rather than a pure male tassel or pure female spike. The developmental morphology of male and female inflorescences of other Zeaspecies should be examined.

Glucose‐6‐phosphatase (G6P) activity was determined in fresh‐frozen, cryostat sections in the shoot apical meristem of Brassica campestrisL. Enzymatic activity was differentially distributed in a zonate pattern in the vegetative meristem, but not in the transition and floral meristem. Vegetative apices showed a heterogenous localization with the highest activity in the central zone and the pith‐rib meristem zone. At the early transition stage of development, G6P activity in the peripheral zone increased slightly. At the late transitional (prefloral) stage, G6P activity was not localized within the peripheral zone in island‐like areas of activity. This is the first demonstration of G6P in shoot apical meristem at the vegetative, transition, and floral stage. The results indicate that G6P activity 1) is an accompanying event of evocation, but 2) does not mark incipient floral primordia. G6P may play an important role in the maintenance of glucose‐6‐phosphate homeostasis in an evoked shoot apical meristem.

An assay system has been developed for the histochemical determination of glyceraldehyde 3‐phosphate dehydrogenase (G3PD) activity to indicate glycolytic pathway capacity during evocation in the shoot apical meristem of Brassica campestrisL. G3PD activity was differentially distributed in a zonate pattern within the meristems at the vegetative, the transition, and the floral stages. The activity of G3PD changed in all apical zones of evoked apices, but especially in the central and the peripheral zones of apices at the prefloral stage. In the prefloral stage of development heavy enzyme activity was localized in island‐like areas within the peripheral zone. These results indicate that 1) the capacity of glycolysis fluctuates during evocation, 2) during floral evocation the capacity of the glycolytic pathway parallels the capacity of the citric acid cycle and the electron transport system only at the prefloral stage, and 3) G3PD activity marks incipient floral primordia. It is proposed that the enzymic marking of an incipient floral primordium indicates the end of evocation in Brassica.

Vegetative plants were induced to flower by 16‐hr‐long days. Apical buds were collected at intervals during several developmental phases up to 63 hr. A stereologic analysis and mitotic index study was conducted on median longitudinal sections of shoot apical meristems. A rise in the mitotic index occurred between 12 and 24 hr within central, peripheral and pithrib meristem zones. Preceding the floral stage a second increase in the mitotic index was observed in peripheral and central zones, but not in the pith‐rib meristem zone. A significant rise in apical volume, cell number, height, and width began in the transitional stage and continued to the floral stage. Significant correlation coefficients were observed between these apical parameters. Relative volume and cell population of each zone remained constant from the vegetative to the reproductive stage. Volume fraction occupied by the nucleus and nucleolus remained constant within each zone during the same time period. In each zone the volume of the nucleus was significantly correlated to volume of the nucleolus. It appears a pre‐inflorescence apex, while larger, is structurally similar to a vegetative apex.

The ontogeny of tassels and ears in two annual Mexican teosintes, Zea mayssubsp. mexicanaand Z. mayssubsp. parviglumis, was examined using scanning electron microscopy and light microscopy. Ear development in these annual teosintes follows a pattern previously described as leading to the bisexual mixed inflorescence in Z. diploperennis.Common bud primordia are initiated in the axils of distichously arranged bracts along the ear axis. These common primordia bifurcate to form paired sessile and pedicellate spikelet primordia. Development of pedicellate spikelets is arrested leaving the sessile spikelets, along with the adjoining rachis segment, to form solitary grains enclosed within cupulate fruitcases. Development of the central tassel spike is similar to that previously described in the Z. diploperennistassel, except that the first formed axillary bud primordia form precocious tassel branches. The origin of these tassel branches suggests a possible mechanism for the transition from a distichous spike, characteristic of teosinte, to a polystichous spike, typical of maize.

The ontogeny of tassels and ears in a perennial Mexican teosinte, Zea perennis(Hitchc.) Reeves and Mangelsdorf, was examined using scanning electron microscopy and light microscopy. Ear development follows a pattern previously described for two annual teosintes, Z. mayssubsp. mexicanaand Z. mayssubsp. parviglumisvar. parviglumis(race Balsas), and for the bisexual mixed inflorescence in a diploperennial teosinte, Z. diploperennis; it differs from that described for the ear of Z. diploperennisplants grown at the latitudes of Iowa and Wisconsin. Common bud primordia of the ear are initiated in the axil of distichously arranged bracts along the ear axis. These common primordia bifurcate to form paired pedicellate and sessile spikelet primordia. Development of the pedicellate spikelets in the ear is arrested leaving the sessile spikelets, along with the adjoining rachis segment, to form solitary grains enclosed within cupulate fruitcases. The organogenesis of the central spike of the tassel is similar to that previously described in other Zeataxa. This developmental study supports the hypothesis that both femaleness and maleness are derived from and expressed on a common background; it is consistent with the view that the maize ear was derived from the central spike of a male inflorescence terminating a primary branch of the main axis of the inflorescence.

A complement of more than 800 soluble proteins was resolved at each of the first five successive stages of early development of the Zea mays ovulate inflorescence by high resolution two-dimensional polyacrylamide gel electrophoresis and a multicolor silver stain. Among the polypeptide complement a subset of 39 occurred that appeared and/or disappeared during the first five organogenic stages of development. All individual subset polypeptides were observed at one or more stages of development, but not all five. The temporal modifications in appearance and/or disappearance of polypeptides during development fell into several distinct patterns. None of these proteins appeared exclusively at either the stage with branch primordia or floral primordia with lemmas. In contrast, the appearance of some proteins in the subset was restricted to only the terminal meristem, the spikelet primordia, or the spikelet primordia with lemmas. Most of the subset polypeptides appeared first in association with spikelet primordia. These observations indicate that early morphologic events of female inflorescence development in maize are linked to a distinctive pattern of protein change.

A method is described for estimating proteins in the same plant tissue sample that is solubilized for separation by two-dimensional polyacrylamide gel electrophoresis. The method uses a modified bicinchoninic acid (BCA) protein assay procedure and a modified standard urea solubilization buffer to estimate microgram values of unknown protein concentration, in the presence of 9 M urea and 4% Nonidet P-40, from a linear standard curve. A method for a quantitative determination of protein concentration by BCA in a sample containing 9 M urea and 4% Nonidet P-40 is also described. This method is effective for the determination of proteins in minute non-green and green plant tissue, and is especially designed for vegetative and floral shoot apices, and the primordia of inflorescences.