Plasticity In Biomass Allocation Research Articles

Competitive ability of two Brassica varieties in relation to biomass allocation and morphological plasticity under varying nutrient availability

Green cabbage (Brassica campestris, leafy variety) and turnip (Brassica campestris var. rapifera, rooty variety) were grown in both monocultures and mixtures at three nutrient levels to investigate their responses to nutrient availability with respect to biomass allocation, morphological plasticity and competitive ability. Their allocation parameters and leaf morphological traits were affected by both nutrient availability and developmental stage. Both of the varieties had a smaller biomass allocation to leaf blades, but a greater allocation to petioles at high nutrient levels. Root:shoot ratio (RSR) of green cabbage decreased with increasing nutrient availability, whereas that of turnip increased. Turnip had a smaller leaf blade weight ratio (LBWR) than cabbage, being compensated for by larger leaf area ratio (LAR) and specific leaf area (SLA). Leaf area ratio and SLA of both the varieties increased with increasing nutrient availability as did their mean dry weights. The mean dry weight of turnip was slightly greater than that of green cabbage in their respective monocultures, while that of green cabbage was greater than that of turnip in their 1:1 mixture. Therefore, green cabbage, having inherently greater biomass allocation to leaves, was generally more competitive than turnip with more biomass allocation to roots, especially at higher nutrient levels. However, within a variety, morphological plasticity (variation in LAR and SLA) was more important than the plasticity in biomass allocation (e.g. variation in RSR and LBWR) in determining competitive ability. The implication of our results is that competition models based on biomass allocation pattern alone may fail to predict competitive outcomes and that such models should also take morphological plasticity into full account.

Plasticity of high and low nutrient‐adapted grasses to added sulfur and nitrogen

Crop and native plants can be characterized as high and low nutrient‐adapted based on their expected response to native and applied nutrients. Our objective was to compare the plasticity of biomass allocation and tissue nutrient concentrations to added sulfur (S) and nitrogen (N) across a continuum of high and low nutrient‐adapted grasses, represented by barley (Hordeum vulgare), smooth brome (Bromus inermis), bluebunch wheatgrass (Pseudoroegneria spicata), and Idaho fescue (Festuca idahoensis). In our greenhouse study, treatments included two S sources (pyrite and gypsum), at 150 and 300 kg S ha‐1, N at 50 kg ha‐1, and a check. Shoot biomass of barley, smooth brome, and bluebunch wheatgrass was enhanced by S plus N. Shoot biomass of barley and smooth brome was greater with pyrite than with gypsum. Root biomass of smooth brome and bluebunch wheatgrass was greater with pyrite than with gypsum. Plant S concentrations of barley and Idaho fescue were enhanced by added S. Plant S concentrations in barley and smooth brome were greater with gypsum than with pyrite. Except for barley, plant S pools (shoot biomass x shoot S concentration) were enhanced with S plus N compared with no added nutrients. Nitrogen pools of barley, smooth brome, and bluebunch wheatgrass were higher with pyrite than with gypsum. Soil sulfate (SO4) was greater when S or S plus N was added than without any added nutrients. For barley and smooth brome, soil sulfate tended to be lower with pyrite than with gypsum. For all soils, pH was lower with added S or added S plus N compared with unamended soils. While pyrite lowered soil pH, gypsum tended to increase soil pH. Overall, barley and smooth brome were highly plastic in responding to enhanced nutrient levels, bluebunch wheatgrass was relatively responsive, and Idaho fescue was least responsive.

Morphological plasticity and regeneration strategies of velvet leaf blueberry ( Vaccinium myrtilloides Michx.) following canopy disturbance in boreal mixedwood forests

The effects of canopy disturbance on the abundance, growth, morphological plasticity, biomass allocation and fruit production of velvet leaf blueberry ( Vaccinium myrtilloides Michx.) were examined in 1996 in a second-growth boreal mixedwood forest near Nipigon, northwestern Ontario that had been logged by either shelterwood cutting or clearcutting in 1993. We found that V. myrtilloides was able to persist in both open and closed canopy boreal mixedwood forests managed for commercial timber extraction. Persistence under heavy shade conditions was accompanied by significant morphological and biomass allocation plasticity. Specific leaf area, leaf area, individual leaf weight, and the proportion of total biomass in stems and foliage changed along an understory light gradient from 0% to 67% percent photosynthetic photon flux density (% PPFD). The degree of above-ground morphological plasticity may explain blueberry's ability to survive under low light conditions. Reproductive performance of V. myrtilloides was greatest under the partial shade conditions associated with shelterwood cutting. Blueberry bushes growing in clearcuts overgrown with 3-year old aspen ( Populous tremuloides Michx.) saplings remained mostly vegetative whereas the number, fresh weight and dry weight of berries in shelterwood cuts was 94% grater than that produced after clearcutting. We attributed the lower fruit yields in the clearcuts to heavy shading from regenerating hardwoods, and mechanical damage to above-ground biomass. The paucity of seedling regeneration as well as extensive mechanical damage to above-ground stems by logging equipment delayed vegetative regeneration of V. myrtilloides in large canopy openings of the clearcut blocks. Unlike other more aggressive ericaceous species (e.g. Kalmia angustifolia var. angustifolia L., Gaultheria shallon Pursh.), V. myrtilloides was unable to resist invasion from faster growing hardwood species (e.g. P. tremuloides) and was rapidly overtopped. V. myrtilloides plants in the uncut control blocks received 3.9% of full sunlight, whereas those growing in the partial cut and clearcut blocks received an average of 25.3% and 32.5% PPFD, respectively. Cover of vegetation over-topping blueberry plants was highest in the uncut forest (90.3%), but was not significantly different between the partial cut (45.5%) and clearcut (50.1%) treatment blocks.

Variation and Plasticity of Biomass Allocation in Daphnia

1. For organisms with indeterminate growth a trade-off between growth and reproduction is expected. The detection of this trade-off depends not only on the covariance between these two traits, but also on the variation of their sum, the total production (TP = growth + reproduction). The smaller the relative variation in TP, the more likely it is to detect the trade-off. To investigate this trade-off, we studied biomass allocation and variation of 56 clones of Daphnia magna from two populations under two food conditions. 2. Broad-sense heritabilities of clutch mass, growth, TP and the allocation ratio (R = clutch mass/TP) were higher in rich than in poor food conditions. Growth and R showed no genetic variation at the low food level

Plasticity in life-history traits of Plantago major L. ssp. pleiosperma Pilger

Plasticity in life-history characteristics was investigated in three populations of Plantago major L. ssp. pleiosperma (Pilger), a self-compatible, wind pollinated species with a high self-fertilization rate. The populations studied were selected for their marked differences in biomass accumulation and habitat characteristics such as nutrient availability and interspecific interaction. Plants, raised from seeds collected at three sites, were grown in a greenhouse at three nutrient levels. In addition, a reciprocal transplant experiment was carried out. In both experiments variances in variables of growth and reproduction were largely due to environmental factors. Besides this overall result, population and population x environment interaction effects existed for most of the variables. Differences in plasticity between populations were further analysed. In the greenhouse experiment plants from a river-side population showed a high degree of plasticity in reproductive effort, whereas plants from two other populations, one series from a beach plain and the other from a salt meadow, showed a high degree of plasticity in shoot-root ratio. Plasticity in biomass allocation to either vegetative or generative parts is suggested to be an important response to selective forces related to either interspecific competition or temporal variability.