摘要:

A series of experiments to determine the effect of light quality and light intensity on sexual expression inEquisetumgametophytes showed that one species,E. arvense, is strongly affected by light intensity; another species,E. hyemale, is strongly affected by light quality; and a third species,E. fluviatile, is relatively unaffected by either light quality or light intensity. Supplementation of mineral media with sucrose indicates that this light effect is not photosynthetic, and in fact suggests that sucrose itself has a morphogenetic effect on sexual determination inEquisetumgametophytes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09985.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Explants of pith parenchyma excised from Romaine lettuce heads(Lactuca sativaLinn. var. Romàna) exhibited xylogenesis after four days dark incubation on a Murashige and Skoog (1962) medium containing auxin (IAA, NAA, or 2,4‐D), cytokinin (zeatin, kinetin, or benzyladenine), sucrose, and agar. With the exception of 2,4‐D, xylogenesis required both an exogenous auxir and cytokinin. The greatest numbers of tracheids were produced by the IAA (5.0 mg/liter)‐zeati (0.1 mg/liter) and 2,4‐D (0.07 mg/liter)‐zeatin (0.1 mg/liter) treatments, whereas the most effective treatment for callus formation was the NAA (0.5 mg/liter)‐zeatin (0.1 mg/liter) medium. In the absence of exogenous cytokinin, 2,4‐D stimulated xylogenesis after 14 days culture at a concentration of 0.02 mg/liter, but was ineffective at 0.07 mg/liter and 0.2 mg/liter. The 2,4‐D treatment induced tracheids to form in small meristematic nodules; aberrant tracheids were also observed. Different patterns in the differentiation of tracheids were associated with the various auxin‐eytokinin treatments. All IAA‐cytokinin treatments produced perpendicular strands around the periphery and tracheid formation throughout the lower half of the explants. The pattern of IAA‐induced xylogenesis was modified by the particular cytokinin employed. Treatment with NAA‐cytokinin induced horizontal strands which were branched, and the xylogenesis pattern was the same regardless of the cytokinin employed. The xylogenesis pattern produced by 2,4‐D‐cytokinin varied with the 2,4‐D concentration, and was independent of the cytokinin employed. Small numbers of tracheids were observed in explants cultured under xylogenic conditions and treated with caffeine (1000 mg/liter) for the inhibition of cytokinesis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09986.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

A complete kinetic analysis of temperature‐induced changes in primary root growth ofHelianthus annuuswas undertaken. Growth rate was expressed in terms of the rate of cell production per file and the average cell length at maturity. Growth rate increased from 0.014 cm · hr−1at 10 C to a maximum of 0.162 cm · hr−1at 25 C and decreased at higher temperatures. The rate of cell production per file, which is dependent on the mitotic cycle duration and the number of proliferating cells in the meristem, reached a maximum of 8.55 cells hr−1at 25 C. The mitotic cycle duration decreased from 46.4 hr at 10 C to a minimum of about 6.3 hr at 30 and 35 C. The mitotic index remained constant between 10 and 35 C. At 30 and 35 C the duration of the S period was about 65% of the total cycle time, while at 10 C it was about 50%. The number of proliferating cells in a meristem remained constant between 15 and 25 C and decreased with further increase in temperature. Therefore, the temperature at which the rate of cell production was maximum was not the temperature at which cycle time was minimum. The maximum length of mature cells occurred between 15 and 30 C. The contribution of each of the above parameters to temperature‐induced changes in growth rate is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09987.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

The rate of leaf development was used for detecting and evaluating growth responses of carnations to environmental factors. Studies were conducted in two separate greenhouses with different temperature, humidity, and soil moisture conditions. Quantitative morphological stages of leaf growth were recorded on a daily basis until buds formed at which time daily bud diam measurements were begun. The cumulative data were transformed into growth rates. Environmental data were obtained daily. Lags in the effect of each environmental factor on growth were obtained by simple correlation analyses using environmental data on the day of growth and each of five previous days. Multiple regression analyses using leaf growth rate or bud growth rate as the dependent variable and environmental data with appropriate lags as independent variables were conducted to determine the relationship of the various environmental factors to growth rate. Equations were developed to predict plant growth under varying environmental conditions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09988.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

A new technique has been employed to trace pollen dispersal in populations ofDelphinium cardinale(Ranunculaceae), a herbaceous perennial native to southern California. Radioactive iodine (I131) was applied directly to fresh pollen on stamens of living plants and subsequently traced and recorded on other plants in the field. While absolute amounts of I131or pollen dispersed were not determined, monitor detection showed that radioactive pollen was dispersed to open flowers (more often to the brightest flowers higher on the plants), and not randomly to stems or unopened flower buds. All dispersal was attributed to hummingbirds—the only observed flower visitors and pollen vectors for these plants. One very denseDelphiniumpopulation had almost 140 lambda of I131applied over 8 days to 76 flowers on six plants in the center of an area 22 m in diam. One fourth of this area monitored after 30 hr showed radioactive pollen on flowers of 8.9% of the 271 flowering stems; 8 days after the first application of I131another fourth of the area showed radioactivity on flowers of 58.2% of the 323 stems in it. A second study area 22 m in diam had 18 lambda of I131applied to 18 flowers on one plant in the center; 64.2% of all (137) flowering stems in the area had radioactive pollen detectable 24 hr later. It is clear that pollen from very few flowers and plants can quickly reach a large proportion of the individuals in such populations. The strongly protandrous nature of the flowers, the frequent flower visits of nectar‐gathering hummingbirds, and the regular adhering of pollen to birds' chins suggest that cross pollination (xenogamy) regularly occurs in these delphiniums. Further study of such pollen vectors' habits and flight patterns, while using pollen tagged with I131, should lead to quantitative expressions of pollen (and gene) dispersal within and among spatially separated plant populations such as these.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09989.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

The plasma membrane in immature cells is often irregular in contour. Some irregularities become conspicuous folds that continue to enlarge into the cytoplasm. These invaginations may continue to increase in size and typically expand into the central vacuole. Sections show two closely parallel membranes in areas where the invagination projects into the vacuole. A narrow layer of cytoplasm may traverse the intermembrane zone between the membranes. The interior of an invagination may lack obvious content, or may be occupied by a fibrous material, or vesicular and tubular structures. The small vesicles bound by a single membrane appear to be derived from a projection formed most frequently near the orifice of the invagination. The origin of large vesicles and tubules possessing one membrane is not certain although they may arise by the fusion of several small vesicles. Alternatively, tubules, once formed, often possess constrictions along their length which suggest that these structures may become divided into a series of smaller vesicles. There is some evidence that cytoplasmic vesicles may fold into the membrane of the invagination and subsequently be pinched off into the interior of the sac. These vesicles are bounded by two membranes. Vesicles frequently contain an electron‐dense content more or less homogeneous in composition and unlike the typical ribosomal character of the cytoplasm. The function of the invaginations or their content remains to be elucidated.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09990.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

The margin of the pinnule inG. linearisbecomes determined early in ontogeny. The bulk of the lamina is derived from an intercalary meristematic band between the margin and the midvein. The sporangiferous receptacle possesses a pronounced tetrahedral apical cell and has over‐all organization comparable to the apex of an axial entity. The receptacle is traceable to the marginal series just lateral to the apical cell of the pinnule. The receptacle is described as neither marginal nor superficial in origin, but apical, and it is interpreted as a branch of the pinnule.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09991.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

The dark transformations of phytochrome were investigated in two members of the Centrospermae:Mirabilis jalapaL. (Four o'clocks) hypocotyl hooks andSpinacia oleraceaL. (Spinach) hypoeotyls plus cotyledons. After an exposure to red light, decay of total phytochrome was observed in both species. No evidence was found for the dark reversion of Pfr2to Prin sections kept in buffer or when decay was inhibited by sodium azide. The rate of loss of total phytochrome under continuous illumination inMirabilishypocotyl tissue depended on the Pfr/Ptotalratio whether maintained by the red or blue regions of the spectrum. The lack of reversion in the species investigated here, as inAmaranthus caudatusL. (Love‐lies‐bleeding) another member of the Centrospermae, suggests that the order is an exception among dicotyledons and in this respect resembles the monocotyledons.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09992.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Excised internodal segments of flowering specimens ofVerbascum thapsus, with and without vascular tissues, were grown on a nutrient medium which lacked added growth regulators such as auxin and cytokinin. Stem segments which contained vascular tissues formed numerous buds in superficial layers of newly formed tissue within two weeks after transfer of the explants to the medium. Tangential cell divisions in the cambium and phloem are thought to be primarily responsible for the newly formed tissue. A regenerated bud displays dendritic trichomes on its first leaf primordium, whereas the earliest that such trichomes appear on intact seedlings is on the second foliage leaf primordium. Pith explants without vascular tissues become brown in a matter of two to three weeks with no visible sign of growth. Endogenous growth regulators supplied by vascular tissues are believed to be major factors in bud formation in excised internodal segments of this species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09993.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Two species of Leguminosae and five species of Rosaceae have been studied in an attempt to determine the relationship between the development of primary vascular bundles and their morphology, and the variation in morphology among vascular bundles of different types in the stem. A residual meristem occurs in all species. The direction of differentiation of provascular tissue and primary phloem is acropetal and continuous, but differentiation of primary xylem is usually basipetal in the stem. Rare acropetal differentiation of primary xylem was observed in two species only, and in these it is restricted to axial bundles. In order to identify the different types of vascular bundles and to understand their relationship to each other and to the organs they supply, the architecture of the primary vascular system was determined. The several types of vascular bundles are highly variable in size and tracheary cell content. Of all the vascular bundles, the leaf traces are the largest and contain the greatest number of files of tracheary elements. Whereas leaf traces gradually increase in size from the levels of their divergence from axial bundles to the levels at which they enter leaf bases, axial bundles maintain a size in approximate proportion to the diameter of the vascular cylinder. Branch traces decrease in size acropetally. In axial bundles there are usually only one or two files of tracheary elements in contrast to as many as nine files in the median leaf traces of some species. In apical regions where the axial bundles are the sole means of continuous longitudinal transport in the stem, effective water and mineral conduction occur through a relatively small number of tracheary elements. In leaf traces, the much larger number of tracheary elements may have, among other functions, adaptive value in compartmentalization of transport.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09994.x

出版商:Wiley    

年代:1971

数据来源: WILEY