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Byline: A. M. Almazan (1), X. Zhou (1) Keywords: Sweetpotato biomass; Sweetpotato storage root; Sweetpotato greens; Biomass yield; Biomass composition; Nutrient film technique; Nutritional quality Abstract: Sweetpotato cultivar TU-82-155 grown in a nutrient film technique system and separated into foliage, tips, fibrous, string and storage roots at harvest had a total dry biomass of 89.9 g per plant with 38.4% inedible portion. Tips and storage roots, the traditional edible parts, were analyzed for dry matter, protein, fat, ash, minerals (Ca, Fe, K, Mg, Na, Zn), vitamins (carotene, ascorbic acid, thiamin), oxalic and tannic acids, and trypsin and chymotrypsin inhibitors to determine their nutritional quality. Water soluble matter, minerals (Ca, Fe, K, Mg, Na, Zn), cellulose, hemicellulose and lignin concentrations in the edible and inedible parts were obtained to provide information needed for the selection of appropriate bioconversion processes of plant wastes into food or forms suitable for crop production in a controlled biological life support system. Author Affiliation: (1) George Washington Carver Agricultural Experiment Station, College of Agricultural, Environmental and Natural Sciences, Tuskegee University, 36088, Tuskegee, AL, USA Article History: Registration Date: 26/05/2006 Received Date: 24/07/1996

Wheat cultivars Malviya 206 and 234 when exposed to 0.15 ppm sulphur dioxide (SO2) for 4 hours per day for 45 days resulted in the reduction of plant length, leaf area, total plant biomass and yield. However, wheat plants with nutrient regime have been found to decrease the level of reduction. Moreover, plants grown under optimal levels of Nitrogen, Phosphorous and Potassium were able to relieve the SO2 induced injury to different extents depending upon the nutrient combinations.

Plant biomass can be used in metal reclamation and remediation of heavy-metal-containing waste streams and sludges. This function of plant biomass is determined by screening for metal uptake efficiency. The screening process, ion-selective binding and preconcentration of metals by different biomaterials are discussed. The mechanisms of metal-binding process are also presented.

Various techniques were employed to examine the mechanism of heavy metal complexation by the dry biomass of the brown seaweed Sargassum fluitans at the molecular level. Information about the amount of strong and weak acidic functional groups in the biomass were derived from simultaneous potentiometric and conductometric titrations. The chemical identification of sulfonate groups and alginate corresponding to 2.25 mmol of carboxyl groups/g of biomass confirmed these results. Modification of these functional groups by methanolic hydrochloride or propylene oxide revealed the major role of alginate in the uptake of cadmium and lead.

We tested whether effects of competition and herbivory on plant growth depend on the aboveground biomass of vegetation. Our objective was to test theoretical predictions about the site-dependence of biotic mechanisms of plant population regulation. Biomass ranged from a mean of 64 to 776 g/m² at the eight study sites, which included six old fields and two herbaceous plant communities near water. To measure effects of competition, 4-5 wk old plants of a perennial grass (Poa compressa) were transplanted into plots where neighboring plants were either left intact or removed and after 4 mo the shoot mass of transplants was compared in the two treatments. Transplants were caged in both treatments to exclude herbivores. Removing neighbors increased transplant shoot mass significantly at all sites, indicating that transplants experienced less competition for resources when their neighbors were removed. Regression analysis indicated that the increase in shoot mass due to neighbor removal was significantly greater at sites with higher biomass. This result supports theories that predict competition should increase with increasing biomass. To measure effects of herbivory, the growth of caged and uncaged plants was compared. Caging transplants did not increase their shoot mass significantly at the two sites with the lowest biomass. However, shoot mass was significantly greater for caged transplants than for uncaged transplants at all other sites. Caged transplants lost less tissue to herbivores such as small mammals and molluscs. Regression analysis indicated that the increase in shoot mass due to caging was significantly greater at sites with higher biomass. The combined effect of herbivory and competition was measured by comparing transplant growth in plots where transplants were caged and neighbors were removed with the growth of transplants in plots where transplants were not caged and neighbors were left intact. Transplant shoot mass was significantly greater where herbivores were excluded and neighbors were removed, especially at sites with high biomass. Our results indicate that competition and herbivory each have a greater effect on plant growth at sites with higher biomass and that herbivory has less effect than competition on plant growth at sites with relatively low biomass., Key words aboveground biomass; competition; herbivory; old field: Ontario, Canada; plant growth; Poa; population regulation. INTRODUCTION One goal of plant ecologists is to develop a model of population density regulation [...]

Production of herbaceous biomass for biofuel seeks to maximize lignocellulose yields and minimize N and mineral (especially K) concentrations in the biomass. Our objective was to relate changes in biomass composition of switchgrass (Panicum virgatum L.) to thermal time [degree days (DD), base = 10 [degrees] C] in several environments. 'Alamo' switchgrass at Stephenville, TX, was sampled weekly or every 2 wk from April to June in 1989 and April to September in 1990, 1991, and 1992. Field plots of Alamo and 'Cave-in-Rock' at Stephenville were sampled 17 times during 1993, and at Blacksburg, VA, were sampled on 11 dates in 1992 and nine dates in 1993 from May to September. Biomass samples were analyzed for lignocellulose, crude protein, total ash, K, and Ca concentrations. Linear and nonlinear regressions were used to relate concentrations of constituents to cumulative DD after burning in spring. Concentrations of each constituent were closely related to cumulative DD and a single equation was able to describe the relationship across several years. At Stephenville, lignocellulose concentrations increased linearly up to 800 to 1000 DD. At Blacksburg, lignocellulose concentrations increased linearly up to 400 to 800 DD after burning. At both locations, the time at which the rapid increase in lignocellulose concentration ended coincided with internode elongation. Crude protein, ash, and K concentrations decreased curvilinearly with accumulated DD. There were no differences in composition between Alamo or Cave-in-Rock at Blacksburg. At Stephenville, Alamo had a greater concentration of lignocellulose than did Cave-in-Rock, but similar concentrations of crude protein, ash, and K. The close relation between DD and composition of switchgrass could be used for predictive purposes.

The financial performance of a biomass-dependent production system was evaluated using an inventory control model. Dynamic programming was employed to examine the constraints and capabilities of producing ethanol from various biomass crops. In particular, the model evaluated the plantation, harvest, and manufacturing components of a woody biomass supply system. Using inventory control to establish biomass harvesting policies is one way of achieving a cost efficient operation. The optimum wood to ethanol production scheme could produce 38 million 1 of ethanol in any given harvest year, a 13.6 million 1 increase over the least optimal policy. Delivered cost was $0.38 [l.sup.-1] consistent with the unit costs from other studies. Nearly 60% of the cost was from the manufacturing component of the system. The remaining costs were attributed to growing biomass (14%), harvest and shipment of the crop (18%), storage of the raw material and finished product (7%), and 'lost sales' (2%). Inventory control, in all phases of production, could influence total delivered costs of ethanol by as much as 62%. A comparison between the least costly wood system and alternative systems further illustrated the benefits of inventory control.

We compared growth and biomass allocation patterns of Lonicera japonica, an invasive vine in the southeastern United States, and its native congener, L. sempervirens, among three herbivory treatments. Growth and biomass variables were calculated at nine harvest dates across 14 mo under no herbivory, insect herbivory, and mammal and insect herbivory. In the absence of herbivory, L. sempervirens accumulated greater biomass and had higher growth rates than L. japonica. Lonicera sempervirens, however, experienced more herbivore damage than L. japonica, particularly due to the combined effects of insect and mammal herbivory. Total biomass accumulation and greater allocation to leaves and stems indicate a compensatory response to herbivory by L. japonica. These attributes in response to herbivory coupled with lower herbivory in its new range compared to L. sempervirens could give L. japonica a substantial advantage over its native congener.

Abstract. Foodchain models predict strong positive response of algal biomass to total phosphorus (TP) in odd-link ecosystems where grazers are controlled by planktivores and no significant response of algal biomass in even-link ecosystems where grazers are released from planktivore predation. On the other hand, resource- or ratio-dependent models predict proportional increase in algal biomass with increasing TP. These predictions were tested with field data from a large number of north temperate lake ecosystems exhibiting a wide range of TP. Instead of using the traditional approach of the number of trophic links present in an ecosystem, I used the presence vs. absence or near absence of large Daphnia and planktivorous fish to indicate the functional dominance of odd vs. even links. Results showed that algal biomass response to TP is stronger in dominant odd-link ecosystems than in dominant even-link ecosystems, which is consistent with the predictions of foodchain models. The significant positive slope of the relationship of algal biomass to total phosphorus for dominant even-link ecosystems is not consistent with foodchain models. In addition, a nonlinear response pattern of algal biomass to total phosphorus appears to be inconsistent with both foodchain and ratio-dependent models. Results also showed that even-link ecosystems produce proportionately lower algal biomass, demonstrating that grazers can modify ratio dependence of algal biomass. Overall, algal biomass appears to be both predator and ratio dependent because grazers are capable of modifying algal response to nutrients, and algae show positive response to nutrients even in the presence of large grazers.

Abstract. The woody [C.sub.3] Prosopis glandulosa (honey mesquite) and [C.sub.4] perennial grass Schizachyrium scoparium (little bluestem) were grown along a gradient of daytime carbon dioxide concentrations from near 340 to 200 [micro]mol/mol air in a 38 m long controlled environment chamber. We sought to determine effects of historical and prehistorical increases in atmospheric [CO.sub.2] concentration on growth, resource use, and competitive interactions of a species representative of [C.sub.4]-dominated grasslands in the southwestern United States and the invasive legume P. glandulosa. Increasing [CO.sub.2] concentration stimulated [N.sub.2] fixation by individually grown P. glandulosa and elicited in [C.sub.3] seedlings a similar relative increase in leaf intercellular [CO.sub.2] concentration, net assimilation rate, and intrinsic water use efficiency (leaf net assimilation rate/stomatal conductance). Aboveground biomass of P. glandulosa was not altered by [CO.sub.2] concentration, but belowground biomass and whole-plant water and nitrogen use efficiencies increased linearly with [CO.sub.2] concentration in seedlings that were grown alone. Biomass produced by P. glandulosa that was grown with S. scoparium was not affected by [CO.sub.2] concentration. Stomatal conductance declined and leaf assimilation rates of S. scoparium at near maximum incident light increased at higher [CO.sub.2] concentration, but there was no effect of [CO.sub.2] concentration on biomass production or whole-plant water use efficiency of the [C.sub.4] grass. Rising [CO.sub.2] concentration, especially the 27% increase since the beginning of the 19th century, may have contributed to more abundant P. glandulosa on [C.sub.4] grasslands by stimulating the shrub's growth or reducing the amount of resources that the [C.sub.3] required. Much of the potential response of P. glandulosa to [CO.sub.2] concentration, however, appears to be contingent on the shrub's escaping competition with neighboring grasses.

The results of mapping standing biomass for a northern forest in Maine, using NASA/JPL AIRSAR polarimetric radar data, is presented. By examining the dependence of backscattering on standing biomass using backscatter modeling and aircraft data, it was determined, in agreement with other recent reports, that the cross-polarized (HV) data from longer wavelengths (L, P-band) were the best radar channels for mapping total above-ground forest biomass. The radar signal appeared to lose sensitivity to changes in biomass for dry biomass levels beyond about 15 kg/[m.sup.2] (150 Mton/Ha). The ratio of HV backscattering from two bands, a longer wavelength P (wavelength = 68 cm) or L band (24 cm) to a shorter wavelength C band (6 cm), enhanced the correlation of the image signature to standing biomass ([r.sup.2] = 0.83 for P/C and [r.sup.2] = 0.79 for L/C) and showed increased sensitivity to dry biomass beyond 15 kg/[m.sup.2].

1 Species composition and biomass of vascular plants were determined in a matrix of 29 sites on the wet eastern slope of Mauna Loa volcano, Hawaii. 2 Sites were sampled at five or six altitudes (914-2438 m a.s.l.) on each of five known-age lava flows (5, 47, 137, 300 and 3400 years BP). 3 The resultant age - climate matrix was used to examine patterns of biomass accumulation, species distribution, and diversity during primary succession. 4 Biomass increased with substrate age and ranged from 0 to over 36 000 g m to the -2 across the matrix. Generally, biomass increased as altitude decreased, although the maximum value was observed at intermediate altitude on the oldest flow. 5 Community composition varied dramatically with substrate age and climate; species richness ranged from 0 to 30 species plot to the -1, with the maximum at low altitude on the oldest flow. 6 Succession was more rapid at low than at high altitude, but followed distinct compositional trajectories at each altitude. A number of species were found solely or primarily as specialists at a particular altitude and/or successional position, while others exhibited broad niches.

1 Year-to-year growth dynamics of a long-lived woodland perennial herb, Paris tetraphylla, were investigated based on the diffusion model. The past biomass growth of each harvested individual was traced back by measuring the rhizome volume between stem scars. The population density was 2.47 m to the -2. Interference between individuals was therefore expected to be almost absent. 2 Two-year field observations revealed that there was little mortality and only a few recruits by seed. Branching of rhizomes (vegetative reproduction or clonal growth) was also very rare. Mean absolute growth rate per year of individuals of biomass x at year t (defined as the G(t,x) function representing averaged species characteristics) was nearly 0 irrespective of x and t, whilst variance of absolute growth rates per year of individuals of biomass x at year t (defined as the D(t,x) function which is caused by environmental fluctuations, genetic variation, etc.) was proportional to x(super b) where b ranged between 1 and 2. 3 Theoretically estimated stationary size distributions of individual biomass based on the above results agreed well with the observed ones, suggesting that the Paris tetraphylla population was already long lived and that the size structure was at a stationary state. The variation factor D(t,x), but not the deterministic factor G(t,x), determined the stationary size structure of the population. 4 It was shown theoretically that fluctuations in mortality rate and the magnitude of the D(t,x) function around the values estimated from the field data affect the stationary size distribution only a little. Therefore, the Paris tetraphylla population studied here is regarded as a stable system. As mortality rate decreases and/or the magnitude of the D(t,x) function increases, stability of size structure increases. 5 The growth and size-structure dynamics of Paris tetraphylla are in striking contrast to those of most crowded annuals and trees, where one-sided or strongly asymmetric competition between individuals is the major determinant of size structure and brings about its stability through the G(t,x) function. Therefore, there are two types of stable plant communities: in one type, such as in most crowded annuals and trees, growth, size structure and stability are governed mainly by the G(t,x) function (i.e. effect of the D(t,x) function is relatively small), and in the other mainly by the D(t,x) function such as in P. tetraphylla studied here and the sparse populations. However, the inverse J-shaped size distribution of individual biomass or stem diameter is common to both types.

In maize (Zea mays L.), a strong reproductive (grain) sink has been associated with increased stalk and root lodging. A weak reproductive sink may result in reduced production of photosynthate. Endosperm mutants sugary1 (su1) and shrunken2 (sh2) reduce the strength of the reproductive sink. Our objective was to examine stalk and root quality, biomass production, and reproductive sink size using su1 and sh2 in near-isogenic backgrounds. In 1989 and 1990, seed of two half-diallels made from six inbreds was planted. The same inbreds were used; however, one diallel used su1 versions of the inbreds and the other, sh2 versions. Each diallel was planted twice; in one planting the su1 and sh2 diallels were pollinated with su1 pollen and in the other, they were pollinated with sh2 pollen. This resulted in four sets of hybrids that varied only for endosperm type. Stalk and root quality and biomass and partitioning traits were measured. Percentage root lodging, root pull resistance, stalk diameter, stalk section weight, and grain yield differed significantly between starchy and sh2 endosperm types. Hybrids with sh2 had less grain yield and root lodging, higher root pull resistance and stalk section weight. Starchy types had a slightly higher harvest index than the su1 endosperm types. There were no significant differences in biomass among the four groups. The significant reduction in reproductive sink caused by the sh2 endosperm was not associated with decreased biomass.

Grassland communities dominated by Festuca scabrella or by Stipa curtiseta and Agropyron dasystachyum were burned experimentally in spring or autumn. Forb, shrub and graminoid biomasses were greater in the unburned Festuca community than in the Stipa-Agropyron type. Spring and autumn burning delayed early season growth of graminoids in both grassland types in the 1st growing season after fire. Peak green biomass was reached later in the season in burned plots relative to reference areas. Plant growth in the spring of the 2nd yr after fire was more rapid in burned plots and peak biomass was reached earlier than in the reference plots. Autumn burning reduced forb biomass significantly early in the growing season during 1 of 3 yr that this parameter was measured. No effect of burning on shrub biomass was detected. Autumn and spring burning of Festuca grassland reduced peak, green, graminoid biomass production in the 1st and 2nd yr after fire; autumn burning had the most negative effect. Reductions in graminoid biomass after burning Stipa-Agropyron stands were smaller than in the Festuca community. Nitrogen concentrations in F. scabrella shoots regrown after fire were higher than those from the reference areas. Soil water content during the growing season, and snow trapping were reduced by burning. Peak green biomass and total graminoid biomass in Festuca grassland recovered to the level of the reference plots 2-3 yr after burning. Recovery was slower in the Stipa-Agropyron community.

Boltonia decurrens (Torrey & Gray) Wood, a perennial species endemic to the Illinois River Valley, is threatened with extinction. Construction of a system of dikes along the Illinois River has altered flood patterns during the last 100 years, converting wet prairies and natural marshes to cropland. Remaining shore habitats have been modified by heavy siltation and altered flooding regimes. Boltonia decurrens is now confined to areas that are disturbed by occasional cropping, disappearing from sites after 3 to 5 years of natural succession. This study was conducted to determine the role of light and water availability upon growth and reproduction. Our data indicate that under greenhouse conditions B. decurrens requires high levels of light for optimal photosynthesis and growth, and is more sensitive to reductions in growth light level than to moderate drought-stress. This sensitivity to light regime may help explain its disappearance from disturbed areas after several years of natural succession. If B. decurrens is overtopped by fast-growing species, it could be shaded to the extent that growth and seed production would be severely affected, increasing the likelihood of its extinction.

The impacts of autumn or spring burning on Symphoricarpos occidentalis were studied in Fescue Prairie in central Saskatchewan. Symphoricarpos density increased two- to three-fold over preburn density in the 1st 2 growing seasons following a burn. Individual shoot weights were approximately one-third those of plants in reference (unburned) sites. Leaves that were approximately two to three times larger, combined with increased stem densities, enabled plants in burned stands to re-establish a leaf area index equal to reference sites within 2 mo of growth in the 1st growing season. Total standing crop of S. occidentalis was reduced only for the early part of the 1st growing season following burning. In the 1st growing season following burning, xylem water potentials and stomatal conductance of burned plants equalled or exceeded those of reference sites. A delayed effect of burning was expressed in the 2nd growing season, with soil moisture, xylem water potentials and turgor potentials being lower in burned plants than in the reference. Flexibility in resource allocation, with a larger proportion of biomass in leaves, and unaffected or improved water status are adaptive features that enable S. occidentalis to regain its position in the plant community the 1st growing season following disturbance by burning. One-time burning in autumn or spring should not reduce the dominance of S. occidentalis in this region.

Tall genotypes of elephantgrass (Pennisetum purpureum Schum.) and energycane (Saccharum spp.) are potential biomass energy plants in subtropical areas because annual dry matter (DM) yields often exceed 40 Mg ha to the -1. A field study was conducted to characterize crop performance of these C4 bunchgrasses during the 35- to 40-wk warm season in north-central Florida. Entries included two tall elephantgrasses (PI 300086 and N51), a tall energycane (L79-1002), and an intermediate pearlmillet (Pennisetum glaucum (L.) R. Br.) X elephantgrass hybrid (S41). In 1989 at Gainesville and in 1990 at another location 20 km away, the grasses were mowed on 28 March and fertilized 1 wk later with 200 kg N, 22 kg P, and 83 kg K ha to the -1. One-time harvests of above-ground biomass were made at 28-d intervals from 16 May through 28 November. Final harvest DM yields (2-yr means) were 46 Mg ha to the -1 yr to the -1 for PI 300086, 47 for N51, 49 for L79-1002, and 37 for S41. Near-linear DM accumulation continued for 140 to 196 d at mean crop growth rates ranging from 18 to 27 g m to the -2 d to the -1. For the tall bunchgrasses, DM production at any point during the season was accurately predicted from canopy height, since height was linearly related to the square root of DM yield (0.87 less than or equal to r squared less than or equal to 0.96). Gross energy yields (2-yr means) in barrels of crude oil equivalent (158.8 L barrel to the -1) were 135 ha to the -1 yr to the -1 for PI 300086, 139 for N51, 141 for L79-1002, and 106 for S41. The high-yielding abilities of the grasses were related to the long linear DM accumulation period.

Elephantgrass (Pennisetum purpureum Schum.) and energycane (Saccharum spp.) have been identified as biomass plants for renewable energy. A field study was conducted at Gainesville, FL, in 1989 and 1990 to identify plant attributes that allowed these C4 bunchgrasses to accumulate high annual dry matter (DM) yields and to compute the efficiency by which solar energy is collected and stored in plant biomass. Entries were PI 300086 (PI3) and N51 elephantgrasses, L79-1002 (L79) energycane, and S41 elephantmillet (Pennisetum glaucum (L.) R. Br. X P. purpureum Schum.). Plots were mowed to 10-cm height on 28 March to begin the season. For PI3, light interception by the top green portion of the canopy was greater than 90% from 49 to 217 d after mowing. For L79, interception increased from 83% on 49 d after mowing to 90% on 91 d and remained above 90% to 245 d after mowing. Two-year means for radiation-use efficiency (RUE), computed for near-linear DM accumulation phase, were 1.25 g DM MJ to the -1 of total solar radiation (TSR) for PI3, 1.26 for N51, 1.24 for L79, and 1.11 for S41. Mean energy concentrations of mature growth ranged from 17.1 to 18.2 kJ g to the -1 DM. Two-year average percentages of TSR converted to chemical DM energy, were 2.3 for PI3, 2.3 for N51, 2.2 for L79, and 1.9 for S41. These bunchgrasses produced greater annual DM yields than other C4 plants because tillers grew vegetatively for 30 to 35 wk. During this period, a green canopy top was maintained and light interception and RUE continued at levels generally expected for actively growing C4 grasses.

Growth of vegetative and reproductive structures in Artemisia tridentata is temporally separated during the growing season; vegetative growth occurs during spring and early summer when soil moisture is most abundant, while reproductive growth occurs during summer and fall when soil moisture may be limiting. Vegetative and reproductive structures may therefore exhibit contrasting efficiencies of resource acquisition and investment resulting from temporal differences in resource availability during their development. We examined the effect of water stress on growth, photosynthesis, and resource investment for vegetative and reproductive modules of Artemisia tridentata by applying supplemental water. No differences were observed in vegetative biomass between shrubs in the two watering treatments. Growth of vegetative structures occurred in the spring when water was not limiting, and shrubs in both watering treatments exerted little stomatal control over water loss. Conversely, reproductive growth occurred through the summer when water was limiting, and supplemental watering increased reproductive growth. Shrubs conserved water during summer by abscising leaves and lowering stomatal conductance of both vegetative and reproductive modules in response to decreases in xylem pressure potential and increases in evaporative demand. Leaf abscission can occur without decreasing the amount of carbon available for reproductive growth because inflorescences are capable of positive photosynthetic rates comparable to vegetative leaves. Water stress did not alter tissue construction costs or carbon and nitrogen contents for either vegetative or reproductive modules. Resource limitations were, however, reflected in the efficiency of water use during tissue construction; floral leaves and floral heads of shrubs not receiving supplemental water were produced with higher water-use efficiency. Conservative use of water during production of vegetative modules would offer no advantage to A. tridentata because neighboring species are also most active at this time. Reproductive growth in A. tridentata occurs during summer when neighboring species are largely dormant, and so efficient use of water may allow development of reproductive structures to continue throughout the summer even with limited supplies of water.

The allometry of reproductive biomass M was determined for one moss (Polytrichum commune), four pteridophytes (Psilophyton princeps, Psilotum nudum, Lycopodium lucidulum, and L. clavatum), six gymnosperms (Larix decidua, Pseudotsuga douglasii, Tsuga canadensis, Pinus rigida, Picea abies, and Taxus baccata), and two angiosperms (Crataegus sp. and Quercus bicolor). Biomass M was measured for individual and grouped reproductive organs and regressed as a function of stem diameter D measured proximal to M for representative reproductive stems from each species. Published data for Cooksonia pertoni were used to estimate sporangial M. The data from this vascular plant fossil were compared to those from other species. Least squares regression of the entire data set yielded M = 0.12D(super 2.9) (r squared = 0.94, N = 215), indicating that M, on the average, compiled with M proportional to D(super alpha approximately equal to 3.0). The allometries of the moss, pteridophyte, gymnosperm, and angiosperm species, however, were M = 0.46D(super 4.6) (r squared = 0.99, N = 41), M = 0.07D(super 3.2) (r squared = 0.91, N = 65), M = 0.56D(super 2.2) (r squared = 0.92, N = 85), and M = 0.44D(super 1.8) (r squared = 0.97, N = 21), respectively, indicating that the proportionality M is proportional to D(super alpha approximately equal 3.0 recedes with finer taxonomic resolution. The data for Cooksonia were found to comply with the allometry of Polytrichum when the regression curve of this moss was extrapolated into the size range of the fossil species. Analyses showed that intraspecific allometric scaling factors alpha were dependent upon the manner in which plant stems taper. Species or portions of branching systems with alpha > 4.0 had essentially untapered stems (e.g., Polytrichum commune, Psilotum nudum, twigs of Larix decidua); species with alpha < 2.2 had tapered stems resulting from secondary growth in most cases. The evolution of tapered primary stems and secondary growth was interpreted to alter reproductive allometry.

Increasing atmospheric carbon dioxide (CO2) levels since the last glacial maximum about 18,000 years ago has resulted in increased biomass and efficiency of water-use in carbon 3 (C3) plants. C3 plants including oats, wild mustard and wheat, were compared with C4 grasses under conditions simulating the atmospheric CO2 concentrations since the last glacial maximum. Water-use efficiency and above-ground biomass of the C3 plants were found to increase linearly with CO2 concentration. Models of the global carbon cycle and its climatic correlates must take into account these effects.

1. Allocation of biomass and nitrogen were studied for 1 year in experimental populations of Carex diandra, C. rostrata and C. lasiocarpa (species from mesotrophic fens) and C. acutiformis (a species from eutrophic fens). These species were grown at two levels of N supply (3 center dot 3 and 20 center dot 0 g N m to the -2 year to the -1, respectively). 2. At low N supply, total biomass did not differ between the species. At high N supply, the total biomass of C. lasiocarpa and C. acutiformis ('high-productive species') significantly exceeded that of C. diandra and C. rostrata ('low-productive species'). In all species, percentage nitrogen allocation to the leaves exceeded percentage biomass allocation to the leaves. 3. The high-productive species had a higher shoot:root ratio, a higher percentage biomass allocation to the leaves (leaf weight ratio, LWR), a higher total nitrogen content and a higher percentage nitrogen allocation to the leaves than the low-productive species. However, the low-productive species had higher leaf nitrogen concentrations (on a weight basis) than the high-productive species. 4. Parameters which are related to light interception, such as the specific leaf area (SLA: m squared of leaf per kg of leaf), the leaf area ratio (LAR: m squared of leaf per kg of plant), the leaf area index (LAI: m squared of leaf per m squared of soil) and the ratio between total leaf area and total root length, did not differ consistently between the high-productive and the low-productive species. 5. Compared with the high-productive species, the low-productive species invested relatively more biomass and nitrogen in plant parts which contribute to the acquisition of below-ground resources. 6. At low N supply, there was a decrease in all species of the shoot:root ratio, LWR, LAR, LAI, and the ratio between total leaf area and total root length. 7. The rank order of potential productivity of the species in this study did not match the rank order of nitrogen availability in their natural habitat. It is suggested that the distribution of these species is not only determined by their potential productivity, but also by specific demands on the water chemistry and by their competitive ability.

1. A growth analysis was conducted on seven annual/perennial pairs of grasses (six congeneric and one pair taken at random) grown in a hydroponic culture system under constant, productive conditions, in order to investigate the mechanisms responsible for the higher relative growth rate (RGR) of annuals as compared to perennials. 2. All the production parameters (RGR, relative leaf production rate, unit leaf rates), were higher in annuals than in perennials. There were very few differences between the two life forms in biomass allocation to the different organs (except a higher allocation to sheaths in perennials). The specific leaf areas and the leaf area ratios were higher in annuals, whereas the dry-weight:fresh-weight ratios of all the organs were higher in perennials. These differences between annuals and perennials were almost systematic when the comparisons were made within a given genus, but not when they were made between annuals and perennials in different genera. 3. The wide range of RGR obtained for the 14 species also permitted general relationships between RGR and the various components of growth to be discussed. RGR was significantly correlated with: (i) unit leaf rate, (ii) specific leaf area, (iii) leaf area ratio, (iv) dry-weight:fresh-weight ratio of the whole plant, and (v) dry-weight:fresh-weight ratio of roots. Surprisingly, RGR was not correlated with any of the biomass allocation parameters. The single factor that best explained the differences in RGR was the specific leaf area. 4. If, as has been hypothesized elsewhere, the annual life form is derived from the perennial one, the results presented here suggest that the same morphological changes have occured repeatedly in different genera. It is argued that these changes, which are probably correlated with differences in anatomical features, mainly affect the specific (i.e. per unit weight or area) uptake capacities of the plant organs, leading to the higher seedling growth rate observed in annuals.

The effectiveness of selected crop biomass inputs at the soil surface is determined. Results show that stover yields significantly increase with irrigation. The incorporated soybean stover is the least effective in developing water-stable soil aggregates in the surface 1.5 cm. Generally, a soil surface with greatly increased rainfall infiltration is obtained in four or five years by a no-till culture that provides about 12 Mg per hectare per year of decomposing crop biomass on the soil surface.

1. Veronica chamaedrys, V. montana and V. officinalis were grown in either shaded or unshaded conditions in a field experiment lasting 18 months. V. officinalis failed to grow beneath shading as a result of slug grazing. Between May and October of the first year, unshaded V. officinalis had the highest relative growth rate (RGR) and shading significantly reduced RGR in both V. chamaedrys and V. montana but to a greater extent in V. chamaedrys. 2. The proportion of biomass allocated to roots was rapidly reduced by shading, but at the end of the experiment differences between species and light environments were negligible. Root phenology was unaffected by shading. In unshaded plants, allocation to stem (SWR) was higher in both V. chamaedrys and V. montana than in V. officinalis. Shading increased SWR and allocation to petioles but only altered stem phenology. The difference in SWR between shaded and unshaded plants of V. montana became less with time. Total allocation to leaves (TLWR) in unshaded plants was ranked V. montana > V. officinalis > V. chamaedrys. The contribution of dead leaves to TWLR was greatest in unshaded plants. Shading increased TLWR in V. chamaedrys but not in V. montana. 3. In unshaded plants, biomass allocation to sexual reproduction was ranked V. officinalis > V. chamaedrys > V. moiziana. Whilst shading reduced allocation to sexual reproduction in V. chamaedrys, it increased allocation in V. montana. Inflorescences were subdivided into: pedicels plus peduncles; capsules plus calyces; and seeds. A second quotient (|relative allocation') was devised by expressing the biomass allocated to each of these subgroups as a proportion of the total allocated to inflorescences. Whereas shading had no influence on relative allocation in V. montana, there was an increase in the pedicel + peduncle component in V. chamaedrys. Pedicels + peduncles accounted for 50% of inflorescence biomass in unshaded V. chamaedrys, but only 30% in V. montana and V. officinalis. Relative allocation to seeds was ranked V. montana > V. officinalis > V. chamaedrys. 4. Growth form, photosynthetic characteristics and slug grazing all hindered the proliferation of V. officinalis under shading. V. officinalis had a high RGR and allocated c. 25% of plant biomass to inflorescences. 5. Shading modified allocation within and between vegetative and reproductive organs of V. chamaedrys. V. chamaedry did not acclimatize to shading; increases in SWR in the second year, coinciding with tree canopy expansion, were supplementary to those incurred in the first year. 6. Shading had little effect on the allocation of biomass within either vegetative or reproductive organs of V. montana: changes detected in previous short-term experiments were transient. At high irradiances, V. montana was susceptible to chlorophyll photodegradation and could not sustain sexual reproductive output.

In Carpinteria Salt Marsh, Salicornia virginica (pickleweed) grows at lower marsh elevations than does Arthrocnemum subterminalis (Parish's glasswort). Standing biomass of both species was greatest immediately adjacent to their abrupt border, suggesting that conditions for plant growth were best here. We utilized field experiments, in which growth rates of naturally occurring and transplanted individuals of both species were measured in four marsh zones, to investigate the role of edaphic factors and competition in maintaining this zonation pattern. The frequency of flooding, and hence soil waterlogging, was greatest at lower marsh elevations, whereas salinity was highest at higher marsh elevations. Consequently, it was not clear, a priori, which part of the marsh had the most severe physical conditions. In our field experiments, both Salicornia and Arthrocnemum grew better in the two middle marsh zones (high Salicornia zone and Arthrocnemum zone) than in either the low marsh (low Salicornia zone), where flooding was frequent and soils were waterlogged, or the high marsh (transition zone), where soil salinity was extremely high during much of the year and plant water potentials very low. However, Salicornia appeared better able to tolerate flooding, and so persisted in the low Salicornia zone, whereas Arthrocnemum appeared better able to tolerate high salinities, and so persisted in the transition zone. Interspecific competition was most important in the relatively benign middle marsh zones, where each species excluded the other from a portion of this prime habitat. In this marsh, flooding, soil salinity, and competition all interacted to determine plant zonation patterns, but the relative importance of these factors varied at different elevations. Key words: Arthrocnemum; competition; edaphic conditions; halophytes; physical gradient; Salicornia; salt marsh; soil salinity; tidal flooding; zonation.

A production model for short rotation, intensive culture (SRIC) plantations was developed to determine the energy and financial costs of woody biomass. The model was based on hybrid poplars planted on good quality agricultural sites at a density of 2100 cuttings ha to the -1, with average annual growth forecast at 16 metric tonne, oven dry (Mg(OD)). Energy and financial analyses showed preharvest costs of 4381 magajoules (MJ) Mg to the -1 (OD) and $16 (U.S.) Mg to the -1 (OD). Harvesting and transportation requirements increased the total costs to 6130 MJ Mg to the -1 (OD) and $39 Mg to the -1 (OD) for the delivered material. On an energy cost basis, the principal input was land, whereas on a financial basis, costs were more uniformly distributed among equipment, land, labor, and materials and fuel.

(1) The relative magnitudes of environmental vs. genetic influences on the growth of Scirpus americanus and Scirpus maritimus were examined in an intertidal marsh on the Fraser River Delta, British Columbia. Intraspecific comparisons at the high and low parts of an elevational gradient were made for shoot, inflorescence, root, rhizome and corm mass over a 16-month period. (2) S. americanus plants on the high marsh had greater shoot densities, flowering frequencies, above- and below-ground masses than plants growing on the low marsh. Shoot density of S. maritimus was highest on the low marsh but its flowering frequency, and above- and below-ground masses were greatest on the high marsh. At all sites sampled, vegetative reproductive effort exceeded sexual reproductive effort; within each species, total reproductive effort on the high marsh exceeded that measured on the low marsh. (3) Shoot growth rates were calculated after controlling for below-ground mass and the duration of tidal exposure. For both species, low-marsh stands had higher shoot growth rates per gram below-ground mass per hour of tidal exposure than high-marsh stands, but shoot mass [m.sup.-2] was greatest on the high marsh. Enhanced plant mass on the high marsh is associated with larger below-ground reserves, but is ultimately a product of prolonged aerial exposure. (4) Reciprocal field-transplant experiments indicated that the high- and low-marsh populations of S. americanus and S. maritimus consist of different genotypes which show similar phenotypes when grown in a common environment. Genotypes moved into new environments grew as well as the residents, suggesting that there is no local genetic differentiation.

Potted fireweeds plants, Epilobium angustifolium L., were grown both from seed and root segments and subjected to early, late, and continuous defoliation and to apical excision during a single growing season. Seed-grown plants and root regenerates compensated completely for the early defoliation treatment and did not differ significantly from controls with respect to the dry weight of any yield component. Late defoliation significantly reduced the weight of flowers and fruit in seed-grown plants and root regenerates, and the annual increment of root weight in root regenerates. Continuous defoliation (early + late) significantly reduced the weight of flowers in seed-grown plants and the weight of both flowers and fruit in root regenerates. Apical excision significantly increased the total weight, shoot weight, and root weight of seed-grown plants but did not significantly affect any yield component in root regenerates. Reproductive allocation, defined as the percentage of total biomass in flowers and fruit, was significantly reduced in both seed-grown plants and root regenerates by the late and continuous defoliation treatments.

A sequential coring approach was used to measure root biomass and production over 1 year in four different communities within the Great Dismall Swamp. A second method, an implanted bag technique, was also used to measure root production, and values were generally lower using this technique. On all sites, fine roots were the most dynamic root component. Both biomass (1,887 g/[m.sup.2]) and production (354-989 g [m.sup.-2] [yr.sup.-1]) were highest on the mixed hardwood site, the least flooded site, and second highest on the cedar site, the site with the longest duration of soil saturation (1,033 g[m.sup.2] and 274-366 g [m.sup.-2] [yr.sup.-1). The maple-gum (696 g/[m.sup.2] and 59-91 g [m.sup.-2 yr.sup.-1) and cypress (824 g/[m.sup.2] and 68-308 g [m.sup.-2] [yr.sup.-1) sites had similarly low amounts of biomass and rates of production. Environmental parameters that influenced production include frequency and duration of flooding, and soil type. Peaks in belowground production were observed on the most productive sites (mixed hardwood and cedar) in summer and late fallwinter; the other two sites exhibited little seasonal variability. The least flooded stand appears to allocate a greater percentage of net primary production belowground than the more extensively flooded stands. The ratio of above- and belowground allocation appears to change in response to a flooding gradient. This has major implications for ecosysten functions as carbon allocation patterns determine the array of litter types generated (leaves vs. roots) which affect decomposition rates and nutrient availability.

Research was conducted to enhance an understanding of the factors controlling phytoplankton biomass and primary production in the zone between 40 and 50 degrees S in summer. A north-south transect along 152 degrees E from 40 degrees S to 50 degrees 30 min S, which was part of a multidisciplinary cruise, was performed from Jan 10-30, 1990. Results demonstrated undersaturation by 50-100 microatmosphere throughout the transect.

The cloning, expression, purification, and characterization of the Thermobifida fusca enzyme, Lam81A, are reported. The microarray analysis has indicated that Lam81A plays a role in biomass degradation and its characterization has shown that the enzyme is specific for [beta]-1,3-linked glucose polysaccharides, is endohydrolytic, and utilizes an inverting mechanism for substrate hydrolysis.