摘要:

Differentiation of the primary thickening meristem (PTM) was investigated in seedlings and older plants ofPhytolacca americanaL. Initiation of the PTM occurs in pericycle or inner cortex at the hypocotyl‐primary root junction of young plants. Differentiation of the PTM in stems occurs acropetally in a cylinder of randomly dividing cells termed the diffuse lateral meristem (DLM). The PTM produces secondary tissue to the inside (internal conjunctive tissue) and to the outside (external conjunctive tissue). Patches of xylem and phloem differentiate, opposite each other, in recently produced internal and external conjunctive tissue, respectively. The resulting strands (desmogen strands) of xylem and phloem are secondary in origin, and are peripheral to primary vascular tissues. Phloem of desmogen strands usually differentiates first. Xylem of desmogen strands is composed of both tracheids and vessel elements; the latter sometimes becoming occluded with tyloses and unidentified substances. As root and hypocotyl increase in diameter, cylinders of PTMs differentiate successively and centrifugally in external conjunctive tissue. Even though the first PTM differentiates in pericycle or inner cortex and later PTMs differentiate in external conjunctive tissue, all are referred to as PTMs because of their similar activity. Multiple rings of desmogen strands can be observed in transections of lateral roots, primary roots and hypocotyls. Throughout the length of the stem, only one ring of desmogen strands is present. Fewer rings of desmogen strands are present in the top of the hypocotyl and cotylendonary node, as compared to the subjacent hypocotyl, due to anastomoses of centrifugally differentiating desmogen strands.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06314.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Presence of buried viable seeds at three depths in freshwater marsh soils was determined by observing seedling emergence in the greenhouse. These results were compared with field germination. For the greenhouse study soils were collected in December 1976, and March 1977, from six vegetation types in the Hamilton Marshes near Trenton, New Jersey. Three to five times more seeds and almost three times as many species germinated in the greenhouse than in the field. Of the ten most numerous species in greenhouse samples, 7.2 ± 0.2 SE species were also observed as seedlings at that site in the field. Annuals comprised seven of the ten most numerous species in both the greenhouse and in the field. Estimated seed densities for the top 10 cm of marsh soil ranged from 6,405 to 32,400 seeds m−2. Germination in soils collected in March was 31% greater than for those collected in December. Decrease in species number with depth was significant for March soils. While seedling numbers also decreased with depth, considerable variability occurred and the differences were not significant. The seed bank profile suggests that viability and/or dormancy are prolonged in these freshwater tidal marsh soils.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06315.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Vetches(Viciaspp.) were studied in the San Francisco Bay Area of California in the spring of 1978. The stipular nectaries of the vetches are visited by the Argentine ant,Iridomyrmex humilisMayr. The nectaries were removed to exclude ants in controlled experiments to determine if these ants protect the vetches from herbivores or seed predators. Plants with excised nectaries suffered substantially greater damage to their foliage than control plants, indicating that ants protect the foliage. There was no indication that ants protect the vetches from seed predators, but fruit set was substantially lower in plants with excised nectaries. Analysis of sugar and amino acid composition of extrafloral nectar served as a basis for feeding tests with Argentine ants by using artificial nectar solutions. Ants preferred sucrose and glucose solutions over fructose. They showed no preference for any one sugar mixture over another, nor did they exhibit differential recruitment to artificial nectar solutions containing only sugars or sugars and amino acids.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06316.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

In previous work with strain 6746 ofLemna paucicostataHegelm. in heterotrophic culture, changes in the light schedule affected certain features of the daily respiratory pattern, on some but not all nitrogen sources, in a manner parallelling their effects on timing in the photoperiodic flowering response. Seeking further guidance on which metabolic processes should be investigated to understand this relationship, twelve additional strains were compared with 6746 in regard to 1) heterotrophic flowering under short‐day skeleton photoperiods, and 2) daily respiratory patterns under 0.25 hr daily of dim red light. Heterotrophic flowering occurred in eight strains; among these, several differed sharply from 6746 in the character of their respiratory patterns and the probable relation of those patterns to photoperiodic timing. For example, in 6746, the second daily peak on NO3, NH4and probably on glutamine reflects photoperiodic timing; the patterns on N‐deficient, aspartate and glutamate media do not. In strains 6609 and 381, in contrast, glutamate also elicits a second peak probably reflective of photoperiodic timing; in strain 421, neither the NO3nor NH4patterns resemble those reflecting photoperiodic timing in 6746. Other strain differences in flowering, respiratory patterns and heterotrophic growth provide useful material for studying phytochrome action, N assimilation and respiration, and they confirm the view that strain identity may be crucial in biochemical investigations on Lemnaceae. These results also reinforce the concept that the “temporal compartmentation” of systems entrained to light/dark cycles can provide important insights, and should be more widely used, in work on regulation of plant metabolism.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06317.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

The morphology and distribution of intracellular crystals of calcium oxalate in taro(Colocasia esculenta)was studied by light microscopy. The modified Pizzolato (AgNO3‐H2O2) method was used to localize crystals in cleared corm cross sections. Crystals of two forms were found: druses and raphides. The numbers and density of the crystals in corms increase rapidly in early development, then level off, and eventually decrease in older and larger corms. An especially high concentration of druses was observed 2‐3 mm from the exterior edge of many corms. This corresponds to a ring of vascular tissue which circumscribes the corm at approximately the same distance from the surface. Observations suggest that the development of these highly specialized cells and the formation of calcium oxalate crystals is a dynamic process.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06318.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

A study of ovule and megagametophyte development in field‐ and greenhouse‐grown plants ofGlycine max(L.) Merrill andPhaseolus aureusRoxb. reveals several consistent features for both species. These features include: a multiple archesporium, enlargement of a primary sporogenous cell directly into a megasporocyte, production of unequal dyad cells, a functional chalazal megaspore,Polygonum‐type development, and a hypostase. A filiform apparatus was not observed in either species. Several marked differences in development also occur.Phaseolususually produces one sporogenous cell per ovule;Glycineproduces 2–3 sporogenous cells per ovule. Meiosis II is synchronous inPhaseolusbut nonsynchronous inGlycine. Linear tetrads are produced inPhaseolus, whereas linear and T‐shaped tetrads are found inGlycine. Starch grains accumulate in the mature megagametophyte ofGlycinebut are absent at that stage inPhaseolus. The usefulness of the modified clearing fluid, benzyl benzoate‐4½, for the study of ovule and megagametophyte development inGlycine maxandPhaseolus aureusis here demonstrated. In addition, the study indicates for both species that megagametophyte development in plants grown under field conditions is markedly similar to development in plants grown in the more uniform conditions of the greenhouse. Accordingly, these findings suggest generally that embryological data collected from plants grown under greenhouse conditions will reflect those from plants found in nature.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06319.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Opening and closure movements of individual stomata were analyzed by light microscopy, scanning electron microscopy, and time‐lapse photomicrography. Turgor‐pressure‐induced changes in pore shape ofCommelina communisL. stomata were observed in vivo and in fixed material. The ventral wall of the guard cells undergoes three‐dimensional alterations during opening and closing. Stomatal aperture increases with increase in light intensity and with decrease in CO2concentration as previously described, while reactions to relative humidity and anaerobiosis are somewhat divergent from common experience. Low humidity induces opening rather than closure of stomata in well watered greenhouse plants, and lack of oxygen induces consecutive opening and closure movements. Individual stomata characteristically open by three distinct steps: (1) rapid opening; (2) immobility or slow closure; (3) relatively rapid opening. Since the timing of the second step varies for individual stomata, it is obscured by methods that integrate the responses of several stomata. The movements of individual stomata are well synchronized, but active communication between stomata in different areas can not be confirmed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06320.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Hydrophyllumis a group of mesophytic herbs occurring in two disjunct groups in North America. The genus is a natural taxonomic entity with the constituent species showing low levels of variability. Morphological similarities of the disjunct species suggest a close affinity betweenH. tenuipesandH. virginianumand a lesser, yet distinct, affinity betweenH. occidentaleandH. macrophyllum. Biosystematic studies that included herbarium comparisons, field descriptions, artificial hybridizations, chromatographic studies, and electrophoretic analyses characterize the interrelationships of the various species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06321.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Two populations ofSagittaria brevirostrafrom the same lake were sampled 10 years apart and yielded similar data on inflorescence structure and on numbers and ratios of male and female flowers. Larger inflorescences have relatively more male than female flowers than do smaller inflorescences. Pollination success is unrelated to inflorescence size or sex ratio within an inflorescence.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06322.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

By making appropriate crosses between heterothallic sexual clones ofDidymium iridiswe can recover apogamic lines in the F1generation. In this organism, heterothallic forms typically produce a haploid myxamoebal stage, but recently two diploid myxamoebal clones homozygous for mating types were discovered. When these are crossed, A2A2xA5A5, tetraploid Plasmodia are produced which later yield diploid F1meiospores. Sixty‐four percent of the single‐spore‐derived clones produce both myxamoebae and Plasmodia, while the remainder do not progress past the myxamoebal stage. These results are consistent with the predictions that from tetraploid nuclei, mating types should segregate in the meiospores in a ratio of 1A2A2:4A2A5:1A5A5, and that myxamoebae heterozygous, A2A5, for mating type should yield Plasmodia apogamously. As the means for verifying relative ploidy levels of myxamoebae and Plasmodia, nuclear DNA was measured with a scanning microspectrophotometer.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06323.x

出版商:Wiley    

年代:1979

数据来源: WILEY