Smaller Plant Size Research Articles

Taxonomy and morphology of the Elymus parviglumis group (Triticeae: Poaceae)

The Elymus parviglumis group, characterized by having relatively small plant size, single spikelets per rhachis node, nodding spikes, and small to medium sized glumes, is revised taxonomically. Previously, a total of twenty seven taxa have been described in this group. In the present treatment, fifteen tetraploid species (2n = 4x = 28) and one interspecific hybrid are recognized, namely, E. antiquus, E. burchan‐buddae, E. sclerus, E. schugnanicus, E. jacquemontii, E. yangii, E. cacuminus, E. retroflexus, E. serotinus, E. altissimus, E. anthosachnoides, E. formosanus, E. longearistatus, E. canaliculatus, E. caucasicus, and E. × russellii. Synonymy, morphological description, cytogenetic data, and a key to these species are presented in this paper.

Macrozoobentos da praia do Codó (Ubatuba, SP) e a presença de Halodule wrightii Ascherson

A year's survey conducted at a seagrass (Halodule wrightii Ascherson) bed and an adjacent bare sand area, on Codo Beach, Ubatuba, southern Brazil, showed that the macrobenthic species composition was different at the two habitats. Surface deposit feeder infaunal polychaetes were the dominant species in the Halodule site and omnivorous/carnivorous and filter feeder polychaetes, in the bare sand. These differences could be explained mainly by the characteristics of the sediment and the stability of the bottom and, secondly, by the presence of Halodule. The presence of vegetation has no effect on density of macrobenthos, probably due to the small size of Halodule plants, which do not support an abundant epifauna. Despite that fact, both number and diversity of species were higher in the seagrass area than in the unvegetated site, as was epifaunal abundance. Significant patterns of temporal fluctuations of macrobenthos abundance and species diversity were not observed, but diversity was the highest in Spring at both habitats. The temporal fluctuations of abundance differed in the two habitats. At the unvegetated site instability of the substrate seems to be responsible for the observed fluctuations in densities. At the Halodule site only light fluctuations occurred, though they did not follow those of macrophyte biomass. Macropredator effects are suggested to be one of the controling factors of macrobenthos density at the vegetated habitat.

Water pumping using a photovoltaic d.c. solar pump without energy storage

A model for the simulation of photovoltaic d.c. solar pumping plants is presented. The model also includes simple meteorological data simulations. The computations are based on an energy balance at the pump input and take into account the effect of meteorological data on the array efficiency and the effect of the configuration instantaneous state on the subsystems efficiency. The results allow explanation of the morning/afternoon dissymmetry of the flow and show that the price of a cubic meter of water can be optimized to improve the benefit/cost ratio. The dissymmetry and the variation of the cubic meter price are explained as follows: small-sized plants are affected by the threshold effect of the pump, and large-sized plants work under a higher manometric head in the afternoon.

112 PRESIDEDRESS SOIL NITRATE TEST FOR SWEET CORN

The presidedress soil nitrate test (PSNT) is an in-season soil test that evaluates the N supplying capacity of soil before side dressing to adjust N application rates. Increasing acceptance of this soil test among field corn growers in New Jersey has shown it to be an effective practice. Nitrogen application rates were reduced by an average of 45 kg-1 ha without loss of crop yield. Field calibration research to extend use of the PSNT to sweet corn has the potential to improve N fertilizer recommendations for this crop. A critical concentration of 25 mg kg-1 NO3-N in the surface 30 cm of soil is generally considered adequate for field corn. Certain crop features of sweet corn (earlier harvest, smaller plant size and population) suggested that the critical NO2-N level might be lower than for field corn while market quality suggested that it might be a higher value. Results from 40 sweet corn field calibration sites in New Jersey indicate that the PSNT critical soil NO3-N concentration may be greater for sweet corn than field corn. A preliminary critical level of 30 mg kg-1 NO3-N in the surface 30 cm of soil is suggested for use of the PSNT on sweet corn. Further research is being conducted to improve sidedress N recommendations based on the PSNT.

Effects of Contrasting Climate and Paclobutrazol on the Growth and Water Use of Two Container-Grown Landscape Plants

Abstract A study was conducted under contrasting climates [southwestern Georgia (humid, temperate) and central Arizona (arid, Sonoran desert)] to evaluate the effects of paclobutrazol on the growth and water use of container-grown Feijoa Sellowiana O. Berg and Ligustrum japonicum Thunb. Plants grown in Georgia were taller, had approximately twice as many leaves and five times more canopy leaf area, a lower shoot:root ratio, and generally higher water use compared to plants grown in Arizona. Differences in meteorological factors such as higher maximum and minimum temperatures and increased solar radiation in Arizona compared to Georgia were coincident with smaller plant size and lower water use of plants grown in Arizona compared to those grown in Georgia. Paclobutrazol inhibited height growth of plants grown in Arizona; however, this growth inhibition was not affected by application concentration. In Georgia, paclobutrazol inhibited height growth of all plants; however, Ligustrum treated with 250 ppm paclobutrazol appeared to begin to overcome growth suppression after five months. Paclobutrazol reduced canopy leaf area and water use for all plants except for Arizona Feijoa.

The effects of crop development upon slug distribution and control by Abax parallelepipedus (Coleoptera: Carabidae)

SummaryThe polyphagous carabid beetle Abax parallelepipedus has been shown to be capable of controlling slugs within a lettuce crop in previous studies. This report describes experiments undertaken in plots within a polythene tunnel. Field slugs, Deroceras reticulatum, were introduced to plots containing either large or small lettuce plants, at 30 slugs per plot. The plots were further subdivided into those with or without six beetle predators. Slug numbers were assessed after two weeks, and were found to be affected by plant size, both with and without the presence of predators. These two factors had an additive effect, with both small plant size and the presence of beetles causing significant reductions in slug numbers. Plots with beetles contained either males or females, and females were shown to be significantly better at reducing slug numbers than males, particularly within plots of small plants. The four principal treatments (combinations of two plant sizes and the presence/absence of beetles) generated four distinct patterns of slug distribution within the plots. The potential of the residual slug populations to inflict further damage was measured in a subsequent crop of seedling lettuces. It appeared that the beetles were generally incapable of capturing slugs within large lettuce plants, but were effective predators at soil level. Possible reasons for the survival of fewer slugs in plots with small plants, both with and without the presence of predators, are discussed.

Leaf expansion, photosynthesis, and water relations of sunflower plants grown on compacted soil

Leaf expansion and growth response of sunflower (Helianthus annuus, L.) to soil compaction were investigated in relation to compaction effects on water relations, nitrogen nutrition, and photosynthesis. A series of field experiments were conducted with plants grown in 20 cm-diameter cylinders with soil bulk densities ranging from 1.2 to 1.7 g cm−3 at the 0–20 cm depth (equivalent to 0.8 to 2.4 MPa soil strength measured with a soil penetrometer). Relative leaf expansion rate (RLER) decreased linearly with increasing soil strength. Smaller plant size in compacted treatments was due not only to slower expansion rates, but also smaller maximum size of individual leaves. Sensitivity of leaf expansion to soil strength was best illustrated by a reduction in RLER and maximum size of the first leaf to emerge in a treatment with only the lower 10–20 cm of the profile compacted (bulk density of 1.7 g cm−3). Root growth was less affected than shoot growth by compaction and root:shoot ratios of compacted treatments were significantly higher than the control.

Les ouvriers et leurs carrières : enracinements et mobilités

ALAIN CHINU Between 1960 and 1990, three men out of ten in the labor force have been blue collar workers throughout their life and three others at some point in their career. Thus, the long term study of occupational and social mobility evidences that most workers' path through the labor force is a complex one : the shift from a blue collar worker position to small firm manager or to white collar positions is fairly frequent. Blue collar workers are most likely to remain in the same position throughout their life in semi-rural small size plants (canning, plastic, carton paper boards, foundry, shoe making industry).

Union-nonunion compensation differentials and industry structure

This paper examines the impacts of industry output and labor (input) market structures on workers' total compensation in U.S. manufacturing. For empirical analysis, CPS May 1983 data were matched with 1982 Census of Manufacturing. Results indicate that employees in highly concentrated product markets [proxied by four-firm concentration ratio (CRR)] earn more. independent of their union membership. Second, union members in the smaller plant sizes have the most to gain and the ‘union advantage’ disappears for medium to large plants. Third, and perhaps most important, the joint effects of unionism and CRR on earnings depend on the size of the manufacturing plant. In conclusion, the paper finds support for Dowrick's (1989) conjecture, that profits-enhancing product market conditions generally tend to increase earnings.

Growth of wild rice ( Z. palustris L.) in fertilized flocculent sediments

Agriform 20-10-5 slow-release and urea fertilizers were used on highly flocculent lake sediments to determine if they would produce commercial yields of wild rice. A small pilot study demonstrated that these fertilizers stimulated wild rice growth, but the results were highly variable because of small plot size and low plant density. Individual yield components generally showed a trend towards increasing production with increasing fertilizer application rate. The rate of maturation of the plant increased with fertilization and may account for some of the variability observed. A model of individual plant response to fertilization was developed using the yield component data of the pilot-scale study. This was incorporated into an econometric model to determine the profit-optimizing fertilizer application rate for whole-lake fertilization. Subsequent fertilization of the experimental lake demonstrated that fertilization of flocculent sediments can result in the production of a commercial crop. Differential effects of fertilization on yield components are discussed and suggestions made for more efficient applications.

Adaptive phenology of desert and Mediterranean populations of annual plants grown with and without water stress.

The dynamics of vegetative and reproductive growth were compared in matched pairs of Mediteranean and desert populations of three unrelated annual species, Erucaria hispanica (L.) Druce, Brachypodium distachyon (L.) Beauv. and Bromus fasciculatus C. Presl., under high and low levels of water availability in a common-environment experiment. Plants of all desert populations showed earlier switches to reproductive development and to subsequent phenophases, and the transition to flowering occurred at smaller plant sizes. Water stress had no effect (E. hispanica) or slightly accelerated the transition to flowering in B. fasciculatus (by 1-2 days) and in B. distachyon (by 4-6 days). Plant senescence was strongly enhanced by water stress, and this enhancement was greater in desert populations than in corresponding Mediterranean ones. Duration of life cycle was greatly shortened by water stress in all three species. Desert and Mediterranean populations of the three species exhibited small differences in their relative response, i.e. phenotypic plasticity, to water stress for phenological and plant size parameters. In E. hispanica and B. fasciculatus the population x water regime interaction amounted to less than 3% of total variance. By contrast, the Mediterranean population of B. distachyon was much more plastic in its response to water stress than the desert population in its transition to plant senescence. Plants from the desert populations appeared to be adapted to shorter, more compact growth cycles, culminating in earlier dates of seed maturation and plant senescence. In addition, they showed larger phenotypic plasticity in the transition to plant senescence, which trait was enhanced or magnified by sustained or repeated lack of water. By contrast, plants from Mediterranean populations delayed switchover from one phenophase to the next, seeming thus to "bet" on more water being forthcoming.

Control of Cotton Aphid, 1989

Abstract Five chemical treatments and an untreated control were compared in 6 row by 1,254-ft plots of cotton grown on 38-inch rows on a commercial farm located near Robstown, TX. All treatments were applied on 4 May and were replicated 3 times in a randomized complete block design. Tractor mounted spray equipment was calibrated to deliver a total spray volume of 10 gal/acre through 2, size 8002 nozzle tips/row at 38 psi. Flat fan spray tips were used due to the wind speed (15-28 mph) and the small size of plants (pinhead square stage). However, wind was blowing exactly parallel with the treatd rows, thus drift between plots was minimal. Insecticide efficacy was measured by (1) counting the no. of aphids on 20 randomly chosen individual plant “key leaves” from the center 2 rows of each plot (the “key leaf was the third leaf down the main stem from the terminal; usually it is the highest fully expanded leaf on the plant), (2) hand harvest of 13.75 row-ft subplots on 10 and 18 Jul at 3 sites from the center 2 rows of each plot, and (3) evaluation of cotton fiber properties. Harvested seed cotton was ginned on a 10-saw Eagle laboratory machine. Lint samples were sent to the International Center for Textile Research and Development, Lubbock, TX for fiber analysis on a High Volume Instrument Tester manufactured by Motion Control.

Functional Morphology of Mountain Plants )

Summary A quantitative survey of the differences in morphology and anatomy in shoots and leaves from contrasting altitudes in different mountain areas, including the tropics, is provided. The majority of data was obtained for herbaceous perennial plants in the Central Alps, where traits of 20 to 30 species from low (600m) and high (3,000m) altitude have been analysed. These results are representative of trends observed in other mountain areas and can be summarized as follows: 1. Individual plants at high altitude occupy 1/5 of the ground area, attain 1/7 of the height, and 1/9 of total shoot leaf area of low elevation taxa, although the mean number of leaves per individual (21) remains similar. Leaf inclination tends to be steeper, and self-shading by leaves and flowers is greater at high altitude. 2. Leaves from high altitude taxa attain 1/11 of the area of leaves of low altitude species. Turgid water content and degree of succulence are not different. At high altitude specific leaf area (SLA) is reduced and leaf thickness is increased. Length and dry matter fraction of petioles are drastically reduced at high altitude. 3. Leaf tissue: in alpine species air space volume in the mesophyll and mesophyll surface/leaf area ratio are one third larger, and the palisade tissue, on an average, consists of 2.7 instead of the 1.7 cell layers found in low altitude forbs. 4. Cell size in leaves and fine roots shows no statistically significant difference between elevations. Some of the highest ranging alpine species exhibit particularly large cells. 5. The thickness of cell walls, particularly in the epidermis, is greater at high altitude. 6. Stomata: Plants from high altitude show a greater fraction of adaxial stomata. In a global comparison stomatal density correlates with the radiation regime and thus shows no uniform altitudinal trend. In most areas investigated, however, density rises with elevation and then declines near the upper elevational limit of a species. A large portion of the leaf characteristics observed at high altitude is lost when plants are transplanted to low elevations. It is suggested that low temperature at high elevation is responsible for small plant and organ size, increased cell wall thickness, and in part, also greater leaf thickness. High light intensities exert additional increases of mesophyll thickness and affect distribution and density of stomata. Nutrient supply and partial pressure of CO 2 appear to be uneffective in this respect. Thus, low temperature and strong light co-determine leaf structures at high altitude in the Alps, leading to highly efficient leaves with respect to photosynthesis (Korner & Diemer 1987). The fact that cell size is not reduced at high altitudes, indicates that mountain plants and their respective organs are small because they produce fewer cells.

Yields of Tomato Phenotypes Modified by Planting Density, Mulch, and Row Covers

Abstract Bare ground (BG), black polyethylene mulch (ML), and polyester row covers with mulch (MRC), combined with three planting densities, provided increasing levels of cropping intensity to study phenotypic response. Four tomato (Lycopersicon esculentum Mill) phenotypes, ‘Sub Arctic Maxi’ (SAM), ‘New Yorker’ (NY), UNH-328 (328), and ‘Westover’ (WVR) represented combinations of small and large plant size and early and late maturity. Early and total yield responses to planting density were linear whether in ML, MRC, or BG treatments, and each phenotype also showed predominantly linear yield increases with increasing density. These linear increases were enhanced in SAM by ML and MRC, but the same mulch and row cover treatments tended to reduce the density response in other phenotypes. The difference was believed to relate to flowering pattern and time relative to vegetative development. Within MRC, compact plants were the most responsive to density in total, but not in early, yield. The predominant effect of ML and MRC was to improve earliness, with each treatment contributing an increment increase in early yield. However, the performance of one phenotype (328) was unchanged by ML or MRC, perhaps reflecting inherent stability.

Effect of incandescent and fluorescent lighting used in photoperiod extension on the vegetative growth and floral development of four lines of pigeonpea

The effects of light quality, as used in photoperiod extension, on vegetative growth and floral development of pigeonpea [ Cajanus cajan (L.) Millsp.] were studied using three photoperiod-insensitive lines, QPL2, Prabhat, and Hunt, and one photoperiod-sensitive line, Royes. Plants were grown in controlled-environment cabinets under day/night temperature regimes of 24/16°C (low) and 28/24°C (high) for 72 days after emergence (DAE). The five light treatments consisted of 12 and 16-h photoperiods and a 12-h photoperiod extended to 16 h with low-intensity lighting from either incandescent (I), fluorescent (F), or incandescent plus fluorescent (I+F) lamps. Little genetic variation occurred in vegetative response (main stem length and node number, leaf area and shoot dry weight) to extension light source. Response varied with temperature, plant age and growth stage. Main stem node appearance and stem extension tended to decline following floral initiation (FI), whereas leaf area and shoot dry weight accumulation increased rapidly after 35 or 42 DAE, irrespective of whether plants were vegetative or floral. Plants were larger under the high-temperature regime. Temperature altered plant response to extension light source. I-extension promoted growth under both temperature regimes, whilst I+F promoted growth under high temperatures but was unexpectedly inhibitory under low. Under high temperatures F extension was inhibitory prior to FI, but promoted later growth during floral bud development (FBD). Under low temperatures, F-extension was not inhibitory during the pre-initiation phase. The four genotypes differed in their floral response to extension light source, the effect on initiation and development of floral primordia varying dependent upon temperature. Low temperatures resulted in sensitivity to extension light source, delaying FI and FBD. In Royes, failure to initiate under low temperatures was associated with small plant size (≤3.5 g shoot dry weight). High temperatures tended to negate the delaying effects of extension light source, but resulted in photoperiod sensitivity, delaying FI in the early-flowering lines QPL-2 and Prabhat. Under high temperatures, Royes was insensitive (FI and FBD) to extensions containing incandescent light (I, I+F). Under high temperatures, time of flowering was least affected by incandescent extensions (I, I+F), and most by F-extension, which delayed FBD in all lines. Under low temperatures, I+F extensions resulted in the greatest variation in flowering time. It was concluded that where heterogeneity exists in floral response to the intensity and/or quality of light, use of artificial lighting to select for photoperiod sensitivity may lead to misclassification.

The Relationship Between Plant Scale and Product Diversity in Canadian Manufacturing Industries

When multiproduct plant economies exist, plant size and diversity decisions are closely linked. The disadvantage of small plant size can be offset by product-packing. The paper shows that within 4-digit industries, larger plant size is associated with greater product diversity. Then a cross-sectional regression at the 4-digit level indicates that Canadian plant size relative to an estimate of US MES is related positively to industry measures of average plant diversity. This suggests that inherent plant scale disadvantages in small economies such as Canada are offset by product-packing.

The Costs of Leaf Support in Understory Palms: Economy Versus Safety

Biomass allocation to nonproductive leaf-support structures represents an inescapable compromise between economy and safety. In the bifid-leaved understory palm species Geonoma cuneata and Asterogyne martiana, the costs of leaf support increase disproportionately with leaf size and crown size. Greater leaf longevities of larger leaves are insufficient to compensate for these escalating costs. Increases in leaf size also entail increases in stresses acting on the petiole, resulting in lower factors of safety in the largest leaves. In Geonoma congesta, ontogenetic changes in leaf morphology from bifid to split leaves at larger leaf sizes result in reduced costs of leaf support relative to bifid juvenile leaves. Despite differences in maximum leaf size, the leaves of reproductive individuals in all three species have similar factors of safety, indicating that mechanical constraints may be limiting leaf size in these species. Although reproductive G. congesta leaves have the greatest leaf-support efficiency (leaf area per unit of support biomass), total leaf area per whole-plant biomass is lowest. In the reproductive stage, plants of G. cuneata, the smallest species, have the highest leaf-support efficiency at leaf and crown levels and the highest total leaf area per whole-plant biomass. These characteristics, largely a consequence of small leaf and plant size, enable G. cuneata to exploit the most heavily shaded microsites within the rain-forest understory.

THE EVOLUTION OF TRACHEID DIAMETER IN EARLY VASCULAR PLANTS AND ITS IMPLICATIONS ON THE HYDRAULIC CONDUCTANCE OF THE PRIMARY XYLEM STRAND.

A cumulative correlation analysis of the maximum diameter of primary xylem tracheids recorded for 41 tracheophyte fossils, plotted against their ages (ranging from the Upper Silurian to the Lower Devonian), yields a Spearman rank coefficient (rsp ) of 0.696 (P < 0.01). Data for specimens taxonomically referable to zosterophyllophytes and lycopods reveal an increase in the range and maximum diameter of tracheids from the Siegenian to the Emsian. Correlation analysis of these data yields an rsp value of 0.95 (P < 0.02). The mean and maximum tracheid diameters recorded for rhyniophytes, when correlated against stratigraphic occurrence, yield rsp values of 0.81 (P < 0.05) and 0.85 (P < 0.02), respectively. A correlation analysis of the data for rhyniophytes, trimerophytes and progymnosperms yields an rsp value of 0.87 (P < 0.01). Therefore, despite a relatively small sample size of early Paleozoic plants, the available data show a surprising level of statistical robustness. The data are interpreted to indicate that during the early evolution of tracheophytes, both the range and maximum tracheid diameter of the primary xylem increased, while in some plant lineages (zosterophyllophytes) there is evidence for a plateauing of maximum tracheid diameters by the Middle Devonian. The statistical trends in the data are interpreted within the context of the evolution of the hydraulic conductance of tracheophyte primary xylem.

Pilot-scale operation and economic assessment of a two-stage, straw—manure fermentation system

A two-stage fermentation system was evaluated. The system consisted of a high-rate fermenter (to produce methane from beef-cattle manure) and a low-rate fermenter (to produce methane from straw and slowly degrading material in the effluent from the high-rate fermenter). Three trials were completed. Results from these trials showed that methane yields of 0.25 m 3 CH 4/kg volatile solids (VS) straw can be achieved in less than 100 days of fermentation at 35°C, and that injection of anhydrous ammonia does not significantly increase the methane yield. Using only the effluent from the straw fermenter as make-up liquid in the system inhibited methane production. This inhibition was attributed to salt accumulation. Based on the assumptions used to design the system (40 Mg total solids (TS) per day) and in the economic analysis, a straw cost of slightly over $15/Mg TS was the break-even cost below which it was economically advantageous to add straw to manure for fermentation to methane. It was economically advantageous to compact the straw to densities between 150 and 300 kg/m 3 to reduce the straw fermenter volume and cost. Economies of scale were apparent, especially at the smaller plant sizes. The discounted cash flow rate of return (DCFRR) increased rapidly up to a plant size of about 20 Mg TS/day, then increased linearly as plant size continued to increase. The plant sizes necessary to achieve a DCFRR of 15% were 6.4, 13, and 43 Mg/day for straw costs of $0, $15, and $30/Mg, respectively. Income tax bracket had only minimal effect on the DCFRR.

Systematics of Bangia (Rhodophyta) in North America. I. Biogeographic trends in morphology

A total of eight species of Bangia have been recognized from North America but only one or two are presently included in taxonomic works. To clarify the systematics of this genus, 84 sites were sampled throughout its range, including south-east Alaska to the Baja Peninsula, Newfoundland to northern Georgia and Lake Michigan to Lake Ontario. Filament length and pigmentation proved to be of little value in differentiating populations. In contrast, significant differences were found when filament diameters were grouped according to the basin from which the samples were collected (P < 0. 001). The mean in situ diameters of monospore releasing filaments from the Pacific, Atlantic and Great Lakes were 157, 91.6 and 75.3 μm, respectively. Similar size differentials were observed for male and female plants in the field. In addition, growth in culture under controlled or varied conditions resulted in a similar trend of basin-based differences in filament diameters for asexual germlings, mature asexual plants or conchocelis filaments. The asexual monospore-releasing plants had average diameters remarkably similar to those of field-collected plants: 163, 91.6 and 74.4 μm for Pacific, Atlantic and Great Lakes filaments, respectively. At least five populations were sampled at each of the type localities of B. enteromorphoides Dawson, B. maxima Gardner and B. vermicularis Harvey. There appears to be no basis for continuing to recognize these populations as being separate from those of the rest of the Pacific. In summary, there are minimally two species of Bangia in North America, representing the populations of the Atlantic (B. atropurpurea (Roth) C. Ag.) and the Pacific (B. vermicularis). The small size of the Great Lakes plants may indicate incipient speciation and hence a new variety may be warranted.