摘要:

Plants ofAgropyron spicatum(Pursh) Scribn. and Smith. from populations native to serpentine and nonserpentine soils were grown at varying levels of magnesium and calcium in culture solutions. The yields of plants from the two populations were different. At high Mg levels (low Ca) the yield of the serpentine population was significantly higher than that of the nonserpentine population. At low Mg the yield of the serpentine population leveled off at a Mg: Ca ratio of 1:2, while the yield of the nonserpentine population increased up to a Mg:Ca ratio of 1:8 and showed no leveling off. Chemical analyses of tissue showed that the Ca uptake of plants from the serpentine population was significantly higher than that of the nonserpentine population. In addition, the serpentine population maintained a lower Mg concentration in the shoots than the nonserpentine population at comparable Mg substrate levels. The two populations showed differences in Ca and Mg uptake efficiency and Mg/Ca, Ca + Mg/K + Na, and Ca + Mg + K + Na in the shoots. The ecotypic differentiation with respect to Mg and Ca between native populations of serpentine and nonserpentineA. spicatumdoes not appear to be due to any single mechanism but, rather, a combination of several possible mechanisms, i.e., differences in root morphology, uptake mechanisms, translocation of nutrients, and interactions between cations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb14032.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

Leaf structure inDoxantha unguis‐catiis polymorphic. The usual mature compound leaf is composed of two lanceolate leaflets and a terminal tripartite spine‐tendril. Leaf primordia are initiated simultaneously in pairs on opposite flanks of the shoot apical meristem by periclinal cell divisions in the third subsurface layer of the peripheral flank meristem. Two leaflet primordia are the first lateral appendages of the compound leaf. Initiation of these leaflet primordia occurs on the adaxial side of a compound leaf primordium 63–70 μm long. Lamina formation is initiated at the base of a leaflet primordium 70–90 μm long and continues acropetally. Mesophyll differentiation occurs in later stages of development of leaflets. The second pair of lateral appendages of the leaf primordium differentiate as prongs of the tendril. Initiation of the second pair of lateral appendages occurs on the adaxial side of a primordium approximately 168 μm long. Acropetal procambialization and vacuolation of cells extend to the apex of tendrils about 112 μm long, restricting the tendril meristem to the adaxial side of the primordium and resulting in curvature of the tendril. The tendril meristem is gradually limited to a more basipetal position as elongation of apical cells continues. Initiatory divisions and early ontogenetic stages of leaflets and tendrils are similar. Their ontogeny differs when the lateral primordia are approximately 70 μm long. Marginal and submarginal initials differentiate within leaflets but not in tendrils. Apical growth of tendrils ceases very early in ontogeny as compared with leaflets.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb14033.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

Germination response to thermoperiod and seedling response to photoperiod‐thermoperiod treatments and to uniform field conditions were compared for 12 populations ofSpartina alternifloraLoisel. from along the Atlantic and Gulf coasts. Germination above 50 % was attained by seeds from all populations in 25–10, 30–15, and 35–20 C alternating diurnal thermoperiods following three months storage in estuarine water at 2–3 C. Except for Massachusetts, Connecticut, and Virginia, seedlings of populations from Ocracoke Island, North Carolina, and northward produced significantly more total biomass in the long‐ than in the short‐day photoperiod in the 30–26 C thermoperiod. Seedling biomass of populations southward of Ocracoke Island, North Carolina, was not significantly affected by photoperiod in either the 18–14 or 30–26 C thermoperiods. Seedlings of all populations from Georgia and northward were significantly shorter and produced significantly more culms in the short‐ than in the long‐day photoperiod in the 30–26 C thermoperiod. Seedlings from Mississippi and all populations from Virginia and northward had significantly lower shoot to root plus rhizome ratios under the short‐ than the long‐day photoperiod in the 30–26 C thermoperiod. Flowering occurred only in populations from Ocracoke Island, North Carolina, northward in the 30–26 C thermoperiod. In a field study, flowering occurred in a north to south sequence and in all populations by the end of the second growing season. Controlled environment and field seedling studies indicated that southern populations flowered later, exhibited longer growing periods, and were less sensitive to photoperiod than northern populations. New England, Mid‐Atlantic, South Atlantic, and Gulf coast populations differed in height, color, flowering time, length of growing period, and morphology through two growing seasons in the field study.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb14034.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

An enzymatic digestion procedure is presented which allows for the isolation of large quantities of mesophyll cells and minor veins ofNicotiana tabacumL. cv. ‘Wisconsin 38’. Isolated mesophyll cells exhibited CO2fixation rates in excess of 150 μmoles CO2mg chl‐1hr‐1, while bundles consistently fixed CO2at much lower rates, viz. 10–20 μmoles CO2mg chl‐1hr‐1. Various physical and biochemical parameters of the isolates have been compared with intact leaf disks.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb14035.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

Leaves ofQuercus velutinaLam. parasitized byTaphrina caerulescens(Desm.) Tulanse were examined with the electron microscope to ascertain cellular aberrations that were induced by the fungus. Major changes were most apparent in the lower epidermis, where cellular divisions and enlargement were common, the cell walls becoming irregularly thickened. Many of the ultrastructural features of the diseased cells resembled those of meristematic cells; the absence of a large central vacuole, a disproportionately large nucleus, and an abundance of cytoplasmic organelles. Chloroplasts with large amounts of starch were also routinely observed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb14036.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

Earlier investigators established that a finger‐like colleter with elongate axial cells and a palisade epidermis is the standard type in the Rubiaceae. This type, with some variation, also prevails inPsychotria, based on a worldwide anatomical survey of vegetative buds from herbarium specimens of 296 species (about 50 % of total). It is virtually the only type found outside of continental Africa. Among African species, it is most common in subgenusPsychotria, with mostly nodule‐free species. In subgenusTetramerae, with only leaf‐nodulated species, there is a strong tendency toward brushlike and dendroid colleters in which epidermal cells are extremely elongate and separated from each other. It is speculated that this change in colleter morphology associated with presence of nodule bacteria may be correlated with a change in secretion product more suitable for support of bacteria. Three morphological forms of crystal occur: raphides, styloids, clustered crystals. They may occur singly or in combination. Several patterns and trends were noted in crystal distribution that could be of taxonomic significance.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb14037.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

A survey of the species of the genusNicotianawas carried out to determine the distribution and the cytological characteristics of heterochromatin in this genus. All examined species of the genus possess knob‐type heterochromatin, which is defined as spherical, densely staining regions of the pachytene chromosomes. These knobs are most frequently located near the centromere, the nucleolar organizer, and the ends of the chromosomes. Block‐type heterochromatin, defined as any longer‐than‐broad heterochromatic segment seen at pachytene, was found in three species of the section Paniculatae, three species of the section Tomentosae, and two species of the section Noctiflorae. Three categories of the block‐type heterochromatin, corresponding to the three subgenera, were found to differ with respect to overall size, staining properties, and location of the blocks. The distribution of these three types of block heterochromatin is discussed in the light of the latest taxonomic treatments of the genus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb14038.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

The distribution of B‐chromosomes throughout the range ofXanthisma texanumhas been determined from approximately 750 individuals from 80 wild populations in Texas, Oklahoma, and New Mexico. Counts of meiotic chromosome figures of n = 4II+ 1 BIand n = 5II(4II+ IBII) are reported for the first time for subsp.texanumvar.texanumand for subsp.texanumvar.orientalis.The wide occurrence of B‐chromosomes in natural populations of subsp.drummondiiis also documented. B‐chromosomes are present in 22 (27.2%) randomly distributed populations whose characteristics are in no way distinct from populations without B‐chromosomes. In populations with B‐chromosomes present, 19.8% of the plants contained one or two B‐chromosomes, but in total only 5.8 % of all plants contained one or two B‐chromosomes. All populations in one isolated population group of subsp.drummondiilack B‐chromosomes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb14039.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

MedullosaandSutcliffiaspecimens from the Paleozoic of North America and Europe are examined to determine the architecture of the cauline vasculature and mode of leaf trace production. Emphasis is placed on the identification and characterization of protoxylem strands and their relationship to leaf trace production. Organization of the primary xylem varies from a single protostele to a dissected stele composed of two to many more or less independent bundles. InMedullosathe bundles of primary xylem are each surrounded by secondary xylem, forming separate segments of vascular tissue (‘steles’ of previous workers). These vascular segments may divide and fuse at different levels in the stem. A definite number of protoxylem strands occur near the periphery of the primary xylem. The protoxylem strands divide at intervals producing protoxylem to the departing leaf traces. Leaf traces thus formed arise from all the vascular segments in a coordinated and predictable way and pass outward through emission areas in the secondary xylem. This type of cauline vascular architecture is compared to that of other seed plants. The vascular system ofMedullosastems is interpreted as a dissected monostele. Sympodial vascular architecture has apparently evolved from a protostele separately within the medullosan pteridosperms.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb14040.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

Apical buds ofXanthiumwere grown in aseptic culture under short‐day cycles known to induce flowering in the intact plants or under “light‐break” conditions known to prevent flowering. The total light provided in each 24‐hr cycle was the same under the two photoperiods. Various numbers of leaves were excised from the apical buds. Excision of leaves did not change the response to photoperiod: even with all leaves excised the apical buds cultured under short‐day conditions reached the same average floral stage as the control buds, and those under light‐break conditions all remained vegetative. Fresh weight was not significantly changed by the excisions, either. However, excision of the young leaves resulted in an increase in the number of new leaves developed by the apical bud during the two‐week culture period.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb14041.x

出版商:Wiley    

年代:1974

数据来源: WILEY