摘要:

Alfalfa (Medicago sativaL.) plants differ in nectar volume production per floret. These differences are heritable, but no information is available on what type of structural variation may be responsible for these differences. One high, one intermediate, and one low nectar‐volume‐producing clone was selected from each of two alfalfa cultivars. Results from light and scanning electron microscopy indicated that alfalfa has an annular nectary located on the staminal column and primarily on the receptacle. It is composed of several cell layers subtended by vascular bundles containing both xylem and phloem. Vascular tissue does not extend into nectariferous tissue. Permanently open stomata are present in the epidermal layer and are thought to function in nectar secretion. These stomata did not respond to stimuli known to affect leaf stomata. Number of stomata per nectary among the six clones ranged from 24.7 ± 1.9 to 6.8 ± 0.5. Nectar‐reservoir diameters among clones ranged from 1.07 ± 0.09 mm to 0.70 ± 0.01 mm. Clones producing the most nectar were characterized by a large nectar reservoir and moderate to high numbers of stomata.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07670.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The first occurrence of attached fertile structures to foliage assignable to the form genusTriphyllopterisSchimper is reported from the early Carboniferous Price Formation of southwestern Virginia. Sporangium‐bearing branch systems consisting of a basal undivided foliar region and a distal much‐divided fertile region are described as a new speciesT. uberisSkog and Gensel. Ovoid fusiform sporangia, 2.0 mm long and 0.5 mm wide and containing trilete spores, terminate ultimate divisions of the branch systems and collectively form masses up to 4 cm in all dimensions.T. uberisis compared to previously known sporangiate organs of Late Devonian and early Carboniferous age, many of which lack attached foliage. Similarities in the overall branching pattern of many of these non‐synangiate, sporangiate organs of early Carboniferous age is noted. The possible mode of dispersal and affinities of the plant bearingT. uberisfertile foliage is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07671.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Lipids and proteins in substantial quantities are present as storage products in spores ofOnoclea sensibilis. They fill the sparce spore cytoplasm and ultrastructurally are indistinguishable from reserve materials observed in storage tissue of higher plants. Hydrolysis of both products is correlated with early stages in spore germination.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07672.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Light and electron microscopy revealed no stimulation of oleosome disappearance or chloroplast development associated with zeatin‐enhanced growth of excised radish cotyledons. Accelerated protein body breakdown was the only detectable effect of zeatin treatment. Isocitrate lyase activity, disappearance of total lipids, and appearance of galactolipids, phospholipids, and chlorophyll were unaffected by zeatin. Results indicate that cytokinins do not accelerate conversion of radish cotyledons from storage to photosynthetic organs.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07673.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The development of radial growth which leads to the pachycaulous form was investigated in eight of the 10 genera of the Cycadales; i.e.,Ceratozamia, Cycas, Dioon, Encephalartos, Macrozamia, Microcycas, Stangeria, andZamia. In all taxa, development of radial growth is essentially the same: a primary thickening meristem is differentiated in the stelar region of the cotyledonary node of the seedling at germination and produces derivatives mainly centrifugally. This primary thickening meristem (PTM) then differentiates acropetally and becomes continuous with the peripheral zone of the shoot apex. At first the PTM is a vertical cylinder, but as the seedling continues to grow into an adult plant, the PTM shows a more horizontal orientation (like an open umbrella) and produces the broad cortex. Secondary growth is by a vascular cambium which produces secondary xylem to the inside and secondary phloem to the outside. The broad pith originates from derivatives of the rib meristem of the massive shoot apex. The seedling and young plant is composed of a shortened shoot (i.e., no internodes) produced by the PTM and rib meristem, and a large fleshy primary root which results from a diffuse growth pattern. Individual cells in both the pith and cortex of the root divide. Their derivatives divide at right angles to the original division plane. Thus, quartets and even octets of cells are recognizable and can be traced to individual parent cells.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07674.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

An essentially unidirectional lateral meristem differentiates in the outer cortex at the hypocotyl‐primary root juncture. This meristem, termed the secondary thickening meristem (STM), then differentiates acropetally towards the shoot apex. It produces secondary tissue (conjunctive tissue) centripetally. Desmogen strands (secondary amphivasal vascular bundles) differentiate from prodesmogen strands in the conjunctive tissue. Root primordia also differentiate from derivatives of this meristem. A primary thickening meristem (PTM) which appears to be continuous with the shoot apex differentiates basipetally. The PTM gives rise to the large primary body of the cortical region of the shoot, and its activity results in the elevation of the leaf bases. In the seedling stages (i.e., for about 2 years) the PTM and STM are longitudinally continuous as a result of the basipetal differentiation of the former and acropetal differentiation of the latter. In adult shoots, however, the two are discontinuous.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07675.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Myrsine floridanaproduces all of its vegetative branches, other than those resulting from pruning or damage, by syllepsis, i.e. by the continuous development of an axillary meristem into a branch without an intervening stage of rest. These sylleptic branches, produced in series, have long and conspicuous hypopodia, broad pith connections with the parent axis, and expanded prophylls. Bud dormancy may be imposed when an axillary meristem is in the axil of the sixth or seventh youngest leaf of the parent shoot. Such axillary meristems may remain at the bud stage with only two pairs of scalelike leaves but these may later give rise to inflorescences or proleptic branches. Proleptic branches lack hypopodia, have narrow piths at their bases, and a series of leaves transitional from the original prophylls to normal foliage leaves within about ten leaves.Myrsine floridanahas cortical bundles in the stem, related to the formation of minor lateral leaf traces. The hypopodia of sylleptic branches, since they are leafless, do not have cortical bundles.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07676.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Ammonium ion induces phenovariation inGymnocolea inflata(Huds.) Dum. (Lophoziaceae) similar in nature to that induced in representatives of four other families of leafy liverworts by antagonists of hydroxyproline‐protein metabolism. That is, in the presence of ammonium ion, ventral leaves developed and the lateral leaf morphology and the branching pattern of the plants changed. These changes, which reflect altered patterns of morphogenesis, were correlated with statistically significant (P ≥ 0.01) differences in peptidyl‐hydroxyproline between normal and NH4+‐induced phenovariant plants. The results support the hypothesis that cell wall‐associated hydroxyproline‐protein plays a morphoregulatory role and that any of a number of factors, genetic, epigenetic or environmental, that could alter the synthesis/distribution of this moiety could cause changes in form.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07677.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Morphometric analysis of orchid seeds indicates that testa and embryo dimensions, color and morphology as well as the presence, absence or nature of reticulation on seed coat walls are of diagnostic value. These studies also point to structure and function correlations in orchid seeds.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07678.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Spermatial differentiation inPolysiphonia hendryibegins after nonpolar, avacuolate spermatia are cleaved from their mother cells. The spermatia and their mother cells are embedded within the spermatangium, a confluent wall matrix of the male branch. As the young spermatium enlarges and becomes ellipsoid, the wall fibrils of the spermatangium are compressed, forming a separating layer. Spermatia become polar with rough endoplasmic reticulum coalescing to form a large, fibrillar spermatial vacuole that becomes extracytoplasmic in later development. Following spermatial vacuole formation, dictyosomes form and deposit a spermatial wall, severing the spermatial mother‐cell pit connection. Enlargement of younger spermatia, which are lateral to the older ones, squeezes the maturing spermatia, pushing them from the male branch, and leaving a scar that compresses and heals. Through this release mechanism, new sites are created for additional spermatial proliferation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07679.x

出版商:Wiley    

年代:1980

数据来源: WILEY