摘要:

Trichome density and type and cannabinoid content of leaves and bracts were quantitated during organ ontogeny for three clones ofCannabis sativaL. Trichome initiation and development were found to occur throughout leaf and bract ontogeny. On leaves, bulbous glands were more abundant than capitate‐sessile glands for all clones, although differences in density for each gland type were evident between clones. On pistillate bracts, capitate‐sessile glands were more abundant than the bulbous form on all clones, and both types decreased in relative density during bract ontogeny for each clone. The capitate‐stalked gland, present on bracts but absent from vegetative leaves, increased in density during bract ontogeny. The capitate‐stalked gland appeared to be initiated later than bulbous or capitate‐sessile glands during bract development and on one clone it was first found midway in bract ontogeny. Nonglandular trichomes decreased in density during organ ontogeny, but the densities differed between leaves and bracts and also between clones. Specific regulatory mechanisms appear to exist to control the development of each trichome type independently. In addition, control of trichome density seems to be related to the plant organ and clone on which the gland type is located. Cannabinoid synthesis occurs throughout organ development and is selectively regulated in each organ. Typically, cannabinoid synthesis occurred at an increasing rate during bract development, whereas in developing leaves synthesis occurred at a decreasing rate. Cannabinoid content on a dry weight basis was generally greater for bracts than leaves. Analyses of leaves indicate that other tissues in addition to glands may contain cannabinoids, while for bracts the gland population can accommodate the cannabinoid content for this organ. The functional significance of trichomes and cannabinoids in relation to evolution is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07774.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Sampling in a soybean field established that presence of velvetleaf (A. theophrasti) weeds interfered with soybean production. Number of soybean pods and number of pods/stem were significantly lower in transect segments adjacent to velvetleaf plants. In bioassays for phytotoxicity of velvetleaf, several dilutions of aqueous extracts from fresh field‐collected leaves depressed germination of radish seeds and inhibited growth of soybean seedlings. Seed germination bioassays from eluates of chromatograms developed in one dimension showed that two of three bands containing phenolic compounds were inhibitory to radish seed germination. Soybeans inhibited by aqueous velvetleaf extracts had increased diffusive resistance, suggesting partial stomatal closure. Inhibited plants also gave evidence of water stress, with leaf water potentials often as low as –20 bars and reduced water content, when compared with controls. Quantification of chlorophyll on a leaf area basis showed that chlorophyll of inhibited plants was below controls. These data demonstrate the allelopathic potential of velvetleaf and suggest that interference with water balance and chlorophyll content may be two mechanisms of inhibitory action of toxins present in the leaves of velvetleaf.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07775.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The timing and patterns of initiation and differentiation of strobili on three clones of loblolly pine located in Washington, N.C., were similar, although the cone‐producing abilities of these clones were significantly different over a 5‐yr period. Male strobili were initiated in early July and were differentiated by mid‐September. Female strobili were initiated about the last week in August and were fully differentiated by mid‐November. There were significant differences in the developmental patterns of the long shoots on these three clones.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07776.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The dynamics of ponderosa pine (Pinus ponderosaDougl.) stands in western North Dakota were studied to determine the influence of plant‐produced chemicals on nitrification rates and competitive interactions within the stands. Ponderosa pine accounted for more than 98% of all tree and shrub stratum stems in this climax community. Low levels of nitrate‐nitrogen relative to ammonium‐nitrogen and low numbers ofNitrosomonasandNitrobacterin the soils indicated that nitrification rates were low. Inhibition of nitrification is often attributed to low soil pH in coniferous forests, but the slightly alkaline soils in this study (pH 7.25–7.75) suggested that another factor caused the low nitrification. Evidence obtained suggested that the reduction in nitrate synthesis was due to the production and subsequent transfer to the soil of secondary plant chemicals that were toxic toNitrosomonas. Chemical inhibitors of nitrification, including caffeic acid, chlorogenic acid, quercitin, and condensed tannins, were found in extracts from ponderosa pine needles, bark, and A horizon soils. These extracts proved to be toxic to soil suspensions ofNitrosomonascausing reductions of from 68–93% of the control. These findings indicate that climax ponderosa pine communities minimize the conversion of ammonia‐nitrogen to nitrate‐nitrogen by chemically inhibiting nitrification.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07777.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The pattern of variation in mature corolla form has been documented throughout the main shoot inflorescence of the cleistogamous speciesLamium amplexicauleL. A heteroblastic development occurs within the cymose inflorescence at a single node as well as between different nodes. Variation involves an increase in cell number and expansion in the upper corolla and also an increase in cell number in the anther sacs, expressed as pollen count increases, in progressively produced flowers in the inflorescence. The corolla base region in all flowers shows an increased cell expansion from the first produced cleistogamous (CL) flowers to the later produced chasmogamous (CH) flowers which expand at anthesis. Cell numbers are equivalent in the corolla base region of all flowers. It appears that in successively produced flowers in the inflorescence, prolonged cell division and expansion occurs in both the upper corolla region and the anthers until a threshold is reached, at which point flowers may undergo anthesis and become CH. The CL corolla form inLamium amplexicauleis not caused by a lack of cell expansion alone; rather, both cell division and expansion are arrested in the upper corolla region.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07778.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Five controlled burns (ca. 2 ha each) were conducted in the Coast Range of northern California near Hopland, California, between November 18, 1975 and September 15, 1976 to determine the effect of shrub phenology on the sprouting response of chamise (Adenostoma fasciculatumH&A) following fire. The time of burn had little effect on the amount of shoot growth that occurred after fire, although the pattern of growth was altered. Shrubs burned on June 22 or August 2, 1976 grew continually until August 1977, while unburned shrubs or those burned at other times ceased seasonal growth during the first summer after fire. Neither the amount nor the pattern of shoot growth was influenced by the shrub water status before the fire occurred. The relationship between chamise shoot growth after fire,14CO2fixation, xylem sap tension, and air temperature was also studied. The growth rate of regrowing shrubs was highly correlated with14CO2fixation prior to the growth measurement. Water status (pre‐dawn xylem sap tension) had a negative correlation with14CO2fixation. The abundance of carbohydrate at the shoot apex is believed to influence the seasonal pattern and rate of chamise shoot growth following fire.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07779.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

A salt marsh species,Jaumea carnosa, was used in hydroponic experiments to test the effects of increasing NaCl concentrations on leaf succulence and plant accumulations of K, Ca, Mg, Na and Cl. A nested experimental design was used with four salinity levels. Plants were grown in full Hoagland's solution plus different amounts of NaCl (0.0–1.2 osmoles). Leaf succulence was measured as percent water content as well as vertical elongation of mesophyll cells. There were no corresponding increases in leaf succulence with increasing concentrations of NaCl in the root zone. Plants receiving aerosol spray (40 mg/dm2/day) did not show significant increases in leaf succulence. Leaf succulence was significantly increased when the plants were removed from the NaCl solutions and placed in non‐salinized Hoagland's solution. Osmotic concentrations of cell sap in leaf tissues showed significant increases as NaCl concentrations increased in the root zone. The concentrations of K, Ca and Mg were higher in plants grown without NaCl than in those grown with NaCl. The accumulations of K in the root tissues were always higher than those of the shoot tissues. Although there was a two‐fold difference in NaCl concentrations at the highest levels, the concentrations of Na in the shoot tissues were relatively similar. The results of the Cl analyses of shoot tissues showed a similar pattern of regulation of uptake. This regulation of salt uptake may be important in preventing injury by limiting accumulations of salt in plant tissues when growing in soils of high osmotic potentials.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07780.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

The effects of salt stress on water balance, growth and anatomy ofJaumea carnosa(Asteraceae) were investigated under field conditions and in greenhouse hydroponic culture experiments. In salt marshes near Santa Barbara, California, soil salinities at root zone varied from 0.37–2.33 osmoles during a 1‐yr study period. These salinities were used to plan hydroponic experiments in a nested experimental design of five salinity treatments. The plants were propagated from rhizome cuttings and were grown in aerated full‐strength Hoagland's solution plus varying amounts of NaCl (range 0.0–2.0 osmoles). Optimum growth was recorded at 0.3 NaCl osmole and the limit of salt tolerance was between 1.2 and 2.0 osmoles. The range of salinity tolerance established for the species in hydroponic experiments was very similar to the range recorded in the root zone in field samples. Dry matter production was significantly lower in plants grown without NaCl than in those grown at 0.3 NaCl osmole. There were no significant differences in saturation water deficit between plants grown at 0.3 and 0.6 NaCl osmole, but the saturation water deficit in plants grown at 1.2 NaCl osmoles was significantly higher than that of plants grown at the lower salt concentrations. As salinity increased both in field conditions and in hydroponic experiments, measurements of anatomical features revealed changes in few of the structural features often associated with salinity stress. With increasing salt concentrations, decreases in internodal length, leaf area, cell size, and stomatal frequency were measured. Diameter of the internode and stele, and thickness of the leaf and stem cuticle showed no significant variations under conditions of increasing salinities. In field samples significant increases in salt concentrations at the root zone during the study did not result in significant increases in leaf succulence. Similarly there were no corresponding increases in leaf succulence with increasing salt concentrations in the hydroponic culture experiments.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07781.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

A study of the morphologies and evolutionary relationships of Upper Carboniferous coal swamp lycopods indicated that plants traditionally treated asLepidodendron hrevifoliumwere distinct fromLepidodendronat the generic level, and were not part of a morphological cline betweenLepidodendronandLepidophloios. The description of a new genus and species by Morey and Morey (1977), based on a specimen identical toL. brevifoliumdistal branches, results in the inclusions ofL. brevifoliuminParalycopodites, in which it has nomenclatural priority overP. minutissimus. The small trees or shrubs had deciduous lateral branches and permanently retained leaves; in these characters,Paralycopoditesis most similar to the compression‐impression genusUlodendronas delimited by Thomas. BisporangiateLepidostrobuscones are closely associated with the vegetative remains; the cones can be assigned to three stratigraphically complementary species throughout the range ofParalycopodites—Visean to Westphalian D (Middle Pennsylvanian). Extreme evolutionary conservatism is indicated by the low vegetative morphological variability and the great similarities in morphology of associated cones; in combination with the sudden Visean appearance ofP. brevifoliusand the lack of intermediates among major lycopod genera, this lends support to punctuated equilibria hypotheses.Paralycopoditeswas generally rare in coal swamps, possibly related to its production of megaspores lacking specialized adaptations for flotation. Its pattern of late Middle Pennsylvanian extinction parallelsLepidodendronandLepidophloios.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07782.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

This study describes a further investigation into the meaning of patterns of cell wall orientation in plants and outlines a modified method for the generation of patterns of principal stresses in a two‐dimensional model. Evidence from simple photoelastic models is presented which supports the concept that the initial location of a presumptive axillary bud primordium may be controlled by mechanical stress in the region of the leaf axil.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07783.x

出版商:Wiley    

年代:1980

数据来源: WILEY