摘要:

In species ofCasuarinawith multileaved whorls, each stem vascular bundle divides radially into two at the site of a leaf trace separation, and the same two bundles rejoin acropetally to where the trace supplies a leaf. Such divisions are divisions of a single vascular bundle, and the rejoining of bundles forms a single bundle. Proposals that the extant primary vascular systems of dicotyledons may have been derived as in conifers are incorrect in so far asCasuarinais concerned, or the system has evolved beyond that so far proposed for dicotyledons. Reasons are offered, however, for considering that fernlike leaf gaps are not present. Leaf traces supply leaves at the first nodes distal to their origins. The ways by which an increase or decrease of stem bundles occur are described. Phyllotactic patterns range from helical (rare) to whorled. In the embryo, where leaves occur decussately, of certain species with multileaved whorls, and in the shoot apices of species with tetramerous whorls, slight differences in the levels of leaf attachments and the bending of leaf traces indicate the probable evolution of extant whorled phyllotaxies from one or more helical arrangements. Stages in the evolution are suggested. The leaves in most species with multileaved whorls are in true whorls. The original periderm of branchlets lies internally to the internodal traces and chlorenchyma, but is otherwise external to the vascular system. It is concluded that each leaf originates at its level of separation from the axis despite several structural features suggesting that the leaf bases have become congenitally adnate to the stem.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07634.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The algal coenocyteCaulerpa proliferaproduces three types of organs, each with a different orientation. The effect of gravity in controlling the development of these organs was investigated. We inverted plants by rotating them 180° around the horizontal rhizome axis, then compared development of the inverted plants with plants matched by size and differentiation. Quantitative data were obtained from photographic records. After inversion the site of organ differentiation was changed with no change in the timing: the next rhizoid (and all subsequent ones) differentiated on the “now‐under side” of the inverted rhizome, the next leaf formed on the “now‐upper side.” Despite the fast change in the site of organ differentiation, other parameters were not changed by inversion (e.g., rate of elongation of rhizomes or leaves, rate of formation of leaves or rhizoids). Because such changes also occurred in plants with balanced lighting from two sides, it is clear that gravity alone can control these changes without reinforcement from top illumination. After leaves were initiated, they did not change their orientation, showing neither positive phototropism (at our light levels) nor negative geotropism, even when elongating substantially. Torsion of the rhizome tip did not precede the change in site of rhizoid initiation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07635.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The anatomy of the stem, root, and leaf ofSimmondsia chinensis(Link) Schneider was investigated, as well as the mode of tissue formation in the stem. Perivascular tissue is present as part of the primary body; outermost cell layers of this tissue mature as a fibrous sheath. The first short‐lived extrafascicular cambium is generated within the remaining parenchymatous perivascular tissue. Successive independent extrafascicular cambia, organized as complete rings or large arcs, arise within peripheral conjunctive parenchyma produced by previous cambia. Extrafascicular cambia produce secondary xylem centripetally and conjunctive tissue bands and strands of secondary phloem centrifugally. Conjunctive tissue initials produce raylike structures of conjunctive tissue; true vascular rays are absent. The phellogen is actually a region of transition where the peripheral conjunctive parenchyma of previous extrafascicular cambia undergoes further cellular subdivision; a true phellogen is lacking. Xylem bands do not represent annual or seasonal growth increments, and secondary growth inSimmondsiais an unequivocal example of the “concentric” anomaly.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07636.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The date palm (Phoenix dactyliferaL.) is a long‐lived, dioecious, arborescent monocotyledon which must be propagated vegetatively by offshoots to maintain clones. An extensive breeding program begun in 1948 at Indio, California, to obtain superior lines has resulted in the production of several seedling populations of known parents. These were used to study the genetic control of isozymes of alcohol dehydrogenase, esterase, glutamate oxaloacetate transaminase, phosphoglucose isomerase and phosphoglucose mutase from leaf tissue. The five enzyme systems are specified by seven polymorphic genes with 14 alleles. Additional polymorphism was found in two other species ofPhoenix. Twenty‐six female and 20 male date palm cvs. were genotyped to provide, insofar as is known, the first single‐gene markers for the date palm and perhaps for any arborescent monocotyledon.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07637.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Bush bean plants (Phaseolus vulgarisL. cv. Contender) were treated once a week for six weeks with simulated acid mist at five pH levels ranging from 5.5 to 2.0. Leaf injury developed on plants exposed to acid concentrations below pH 3 and many leaves developed a flecking symptom similar to that caused by ozone. An adaxial, interveinal bleached area resembling SO2injury also developed on some trifoliate leaves at the low pH treatments. Microscopic observation of injured trifoliates indicated that the palisade cells were plasmolyzed and that the chloroplasts lost structural integrity. Reductions in plant weight and chlorophyll content were detected across the pH gradient. Seed and pod growth were reduced at some intermediate acid depositions even though no visible foliar injury developed. Foliar losses of nitrogen, calcium, magnesium and phosphorous increased with decreases in acid mist pH, whereas foliar potassium concentrations were unaffected by acid mist treatment.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07638.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

At germination the shoot apical meristems ofEchinocereus engelmanniiwere discs with a volume of 666,000 μm3and were composed of a unistratose tunica (volume: 260,000 μm3) and a corpus which was two cell‐layers thick (volume: 406,000 μm3). Four days after germination the nucleus constituted 28.9% of the volume of the cell, and the vacuole constituted 24.5%. The mitochondria were 13.3% of the volume of the tunica cytoplasm, the chloroplasts 9.4%, and the dictyosomes only 1.2%. The endoplasmic reticulum was too sparse to be accurately measured. The organelles of the corpus were identical in size and shape to those of the tunica, but there were statistically significant differences in their cellular and cytoplasmic densities: the more distal corpus layer (C1) was less vacuolate (16.6% of the cell volume), and both corpus layers contained more chloroplasts, 12.0% of the cytoplasmic volume in C1 and 14.3% in the more proximal corpus layer (C2). During the first four days after germination there was a dramatic increase in the size of the central vacuole (e.g., from 15.4% to 24.5% in the tunica), and the mitochondria increased in density from 10.2% of the cytoplasmic volume to 13.3%. Chloroplast density also increased in all meristem layers, but the dictyosome density decreased, as much as a 30% loss in C2. There was also a highly significant reduction in the number of cisternae per dictyosome, from 5.47 to 4.77. Surprisingly, there was no change in heterochromatin: ca. 27% of the volume of the nuclei of all layers was heterochromatic at all stages studied. Thus, the organellar structure of corpus cells is distinctly different from that of tunica cells, and as the apical meristem becomes active after germination, the changes which occur are not uniform in the meristem but rather are zone‐specific.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07639.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The floral biology ofNelumbo pentapetala(Walter) Fernald, the American lotus, native to Texas, was investigated. Anthesis occurs over three consecutive days with flowers opening each morning and closing around noon. First‐day flowers are protogynous with the perianth parts partially expanded so that pollen‐covered insects which are attracted by floral color and the intense “fruity” odor (diffused with the aid of increased floral temperature) are directed on to the flattened receptacle (= carpellary receptacle) from which the receptive stigmas protrude, thus accomplishing pollination. During the second morning anther dehiscence begins and insects which visit and forage within the flower become covered with pollen and typically crawl over the still receptive stigmas achieving “facilitated” self‐pollination (indirect autogamy). By mid‐morning of the second day the stigmas dry and become non‐receptive to pollen. During the third day of anthesis perianth and staminal parts quickly abscise and over the period of a few weeks the receptacle and enclosed fruits mature. In most populations studied, Hymenoptera (e.g.,Lusioglossumspp., andApis mellifera) were the most abundant and effective pollinators. In some populations, however, Coleoptera (e.g.,Chauliognathus) were also numerous and effective pollinators. It is suggested that the overall floral structure (e.g., large numbers of stamens, masses of pollen, staminal appendages) are adaptations which facilitate the pollination ofNelumboby beetles.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07640.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Developing sieve elements of pennycress (Thlaspi arvenseL.) were studied with the electron microscope. The maturation of sieve elements involved loss of ribosomes from cytoplasm; degeneration of nulcei; modification of endoplasmic reticulum (ER); loss of tonoplast; and disappearance of dictyosomes and dictyosomes vesicles, coated vesicles, microtubules, and microbodies. Such changes produce a mature, presumably conducting cell that contains no nucleus or central vacuole but which retains a thin layer of peripheral cytoplasm with plastids, mitochondria, and smooth ER. Some similar changes have been described in a variety of developing sieve elements of angiosperms, but coated vesicles and microbodies previously have not been followed through sieve‐element maturation. Likewise, few developmental studies have been made of plant sieve elements that exhibit two types of P‐protein, the tubular type and the granular P‐protein body.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07641.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Three protein polymorphisms and annual width increments measured from cores were used to study the ecology and evolution of quaking aspen,Populus tremuloidesMichx., in the Front Range of Colorado. Correlations among elevation, age and diameter of the largest standing ramet, and sex and mean growth rate of 106 clones are reported and discussed. The variance of growth rate was apportioned within and among ramets of a clone; the majority of the variance is environmental, with broad heritability estimated as less than or equal to .32. Analyses of gene and genotypic frequencies of polymorphic proteins revealed little differentiation with elevation, but substantial differences between the sexes. For one of three pairwise tests, the genotypes are not distributed independently of one another; linkage disequilibrium between a peroxidase locus and phosphohexose isomerase is significantly different from zero. Multiple regression revealed a positive correlation between mean growth rate and degree of heterozygosity.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07642.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The caloric content of pollen for several different species was determined by using a semimicro oxygen bomb calorimeter. The species studied were divided into subsets for statistical comparisons. The subsets considered were wind‐pollinated dicots, monocots and gymnosperms; insect‐pollinated dicots; and taxonomic subclasses of the wind‐pollinated angiosperms (Asteridae, Hamamelidae, Caryophyllidae and Commelinidae). The results indicated a statistically significant caloric content difference (0.05 or higher) between wind‐pollinated dicots vs. monocots and gymnosperms. There was no statistical difference between wind‐pollinated dicots and insect‐pollinated dicots. All subclasses were significantly different from one another. A statistically significant difference was found between two tribes in the Asteraceae which have shifted from insect to wind pollination, providing additional evidence for an independent evolution of the two. The need for future research in this area is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07643.x

出版商:Wiley    

年代:1980

数据来源: WILEY