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Pascal Nzokou and Bert M. Cregg

and 26 Sept. 2008). Height and diameter growth were calculated as the difference between the final and initial measurements. Ten trees were randomly selected and used determination of the initial root, stem, and foliar biomass in May 2007. At the end

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Handell Larco, Bernadine C. Strik, David R. Bryla, and Dan M. Sullivan

ammonium sulfate also affected biomass accumulation and allocation ( Bañados et al., 2012 ); however, the impact of organic fertilizers on blueberry growth and allocation has not been reported. Organic blueberry farmers commonly use fertilizer products

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Au Trung Vo, Imane Haddidi, Hussein Daood, Zoltan Mayer, and Katalin Posta

plants were watered two times a week for 7 weeks. Each treatment had 10 biological replicates. Assessment of plant growth rate and biomass. Plants were harvested after 7 weeks of growth; fresh and dry weight of shoots, roots, and leaf area were estimated

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André Snyder, Matthew J. Morra, Jodi Johnson-Maynard, and Donald C. Thill

species, but may also differentially affect the microbially mediated soil N cycle. Our objectives were to assess the effects of three Brassicaceae seed meals with different GLS profiles and similar N contents on plant growth and seasonal N mineralization

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K.T. Morgan, J.M.S. Scholberg, T.A. Obreza, and T.A. Wheaton

Growth and nitrogen (N) accumulation relationships based on tree size, rather than age, may provide more generic information that could be used to improve sweet orange [Citrus sinensis (L.) Osbeck] N management. The objectives of this study were to determine how orange trees accumulate and distribute biomass and N as they grow, investigate yearly biomass and N changes in mature orange trees, determine rootstock effect on biomass and N distribution, and to develop simple mathematical models describing these relationships. Eighteen orange trees with canopy volumes ranging between 2 and 43 m3 were dissected into leaf, twig, branch, and root components, and the dry weight and N concentration of each were measured. The N content of each tree part was calculated, and biomass and N distribution throughout each tree were determined. The total dry biomass of large (mature) trees averaged 94 kg and contained 0.79 kg N. Biomass allocation was 13% in leaves, 7% in twigs, 50% in branches/trunk, and 30% in roots. N allocation was 38% in leaves, 8% in twigs, 27% in branches/trunk, and 27% in roots. For the smallest tree, above-/below-ground distribution ratios for biomass and N were 60/40 and 75/25, respectively. All tree components accumulated biomass and N linearly as tree size increased, with the above-ground portion accumulating biomass about 2.5 times faster than the below-ground portion due mostly to branch growth. The growth models developed are currently being integrated in a decision support system for improving fertilizer use efficiency for orange trees, which will provide growers with a management tool to improve long-term N use efficiency in orange orchards.

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Conny W. Hansen and Jonathan Lynch

Whole-plant biomass accumulation, P dynamics, and root-shoot interactions during transition from vegetative to reproductive growth of `Coral Charm' chrysanthemum (Dendranthema ×grandiflorum Ramat.) (Zander, 1993) were investigated over a range of P concentrations considered to be deficient (1 μm), adequate (100 μm), and high (5 mm). In nondeficient plants, transition from vegetative to reproductive growth resulted in reduced relative growth rate and root and shoot biomass accumulation. Reproductive plants showed a higher commitment of the whole plant to the production of developing flowers than to leaves and roots, whereas, in vegetative plants, the highest component production rate was in leaves. This indicates changes in the source-sink relationships during transition from vegetative growth making developing flowers stronger sinks for photoassimilates than roots. Phosphorus allocated to developing flowers was predominantly lost from leaves. Phosphorus-deficient plants showed characteristic P-deficiency symptoms and favored root growth over shoot growth regardless of growth stage. Phosphorus availability in nondeficient plants affected root growth more than shoot growth. No substantial differences in shoot biomass production, relative growth rate, and CO2 assimilation rates were observed in adequate-P and high-P plants. However, the root component production rate, root to shoot ratio, root length ratio, specific root length, specific root area, root mass to leaf area ratio, and root respiration increased in adequate-P plants compared with high-P plants, which indicates that high root activity was maintained without affecting shoot biomass in buffered P conditions. Our results suggest that the high P concentrations used in many horticultural systems may have no benefit in terms of shoot growth and may actually be detrimental to root growth.

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Rinaldi Laura*

Olive plants for commercial production are vegetatively propagated by cutting and grafting. While genetic identity can be maintained by “own root”; plants by cutting, the grafted plants may show different growth characteristics due to the influence of the rootstock. The selection of mother plants, able to produce seeds with desirable characteristics and rootstocks that may control seedling growth in grafted stock, can be an objective of study to facilitate the development of olive breeding programmes. The relationship between seed biomass, mineral nutrient reserves, time to germination and seedling growth was analysed for six cultivars of Olea europaea. The cultivars, exhibiting initial differences in seed biomass, differed significantly with respect to germination capacity, germination time and mineral content. Significant variation among cultivars was also evident in the linear growth of seedlings, evaluated at different intervals from 2 to 30 weeks. The seeds from all six cultivars exhibited low germination. There is a significant effect of cultivar on the levels of single mineral nutrient content of seeds, high concentrations of N and significant concentrations of K, P, Mg, and Ca were detected. Seed biomass was not related to time to germination and the levels of single nutrients of the seeds themselves. For seed tissue, significantly positive correlations existed only between K, and Mg concentrations. Seed biomass was positively and significantly related to root biomass. The seedlings obtained from larger seeds showed a substantially greater proportion of biomass to roots. Some root traits may be important for survival and the establishment of the seedlings, not least under conditions of limited water availability.

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D.G. Mortley, C.K. Bonsi, P.A. Loretan, W.A. Hill, and C.E. Morris

Growth chamber experiments were conducted to study the physiological and growth response of sweetpotato [Ipomoea batatas (L.) Lam.] to either 50% or 85 % relative humidity (RH). Vine cuttings of T1-155 were grown using the nutrient film technique in a randomized complete-block design with two replications. Temperature regimes of 28/22C were maintained during the light/dark periods with irradiance at canopy level of 600 μmol·m-2·s-1 and a 14/10-hour photoperiod. High RH (85%) increased the number of storage roots per plant and significantly increased storage root fresh and dry weight, but produced lower foliage fresh and dry weight than plants grown at 50% RH. Edible biomass index and linear growth rate (in grams per square meter per day) were significantly higher for plants grown at 85 % than at 50% RH. Leaf photosynthesis and stomatal conductance were higher for plants at 85 % than at 50% RH. Thus, the principal effect of high RH on sweetpotato growth was the production of higher storage root yield, edible biomass, growth rate, and increased photosynthetic and stomatal activity.

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Leopold M. Nyochembeng, Caula A. Beyl, and Rodulfo P. Pacumbaba

Current goals for space exploration are predicated upon long-term manned space flights and colonization of planetary habitats. Long periods in space without payloads of necessary items from Earth require the development of a self-sustaining ecosystem that will allow astronauts to grow their own food and efficiently recycle the waste products. Crops suggested for growth in space include wheat, rice, carrots, soybean, mushrooms, etc. Optimal and rapid biodegradation of lignin and other cellulosic material of crop residues by candidate edible white rot fungal strains is paramount in the use of these organisms to achieve effective biomass recycling in an advanced life support system (ALS). The incorporation of organic N into the substrate and pairing crop residues may enhance growth and fruiting of the edible fungi, thus increasing the rate of biodegradation of the substrates and biomass recycling. We investigated the mycelial growth of two strains of Pleurotusostreatus (`Grey Dover' and `Blue Dolphin') on processed single vegetative residues of soybean, cowpea, tomato, sweetpotato, or their 1:1 combination with wheat or rice straw. Growth and fruiting of the two strains including another strain (`Pohu') on rice straw mixed with solid thermophilic aerobic reactor (STAR) effluent for degradation and recycling were also studied. Mycelial growth and fruiting in `Grey Dover' and `Blue Dolphin' were significantly repressed on sweetpotato and basil; however, growth of the two strains was improved when sweetpotato and basil substrates were paired with rice or wheat straw. Fruiting was prolific in paired combinations of soybean with wheat or rice straw. High concentration of STAR residue enhanced mycelial growth; however, a relatively lower concentration was required for abundant fruiting.

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Clyde Wilson, Xuan Liu, Scott M. Lesch, and Donald L. Suarez

Over the last several years, there has been increasing interest in amending the soil using cover crops, especially in desert agriculture. One cover crop of interest in the desert Coachella Valley of California is cowpea [Vigna unguiculata (L.) Walp.]. Cowpea is particularly useful in that as an excellent cover crop, fixing abundant amounts of nitrogen which can reduce fertilizer costs. However, soil salinity problems are of increasing concern in the Coachella Valley of California where the Colorado River water is a major source of irrigation water. Unfortunately, little information is available on the response of cowpea growth to salt stress. Thus, we investigated the growth response of 12 major cowpea cultivars (`CB5', `CB27', `CB46', `IT89KD-288', `IT93K-503-1', `Iron Clay', `Speckled Purple Hall', `UCR 134', `UCR 671', `UCR 730', `8517', and `7964') to increasing salinity levels. The experiment was set up as a standard Split Plot design. Seven salinity levels ranging from 2.6 to 20.1 dS·m–1 were constructed, based on Colorado River water salt composition, to have NaCl, CaCl2 and MgSO4 as the salinization salts. The osmotic potential ranged from –0.075 to –0.82 MPa. Salt stress began 7 days after planting by adding the salts into irrigating nutrient solution and ended after 5 consecutive days. The plants were harvested during flowering period for biomass measurement (53 days after planting). Data analysis using SAS analysis of variance indicated that the salinity in the range between 2.6 and 20.1 dS·m–1 significantly reduced leaf area, leaf dry weight, stem dry weight and root dry weight (P ≤ 0.05). We applied the data to a salt-tolerance model, log(Y) = a1 + a2X + a3X2, where Y represents biomass, a1, a2 and a3 are empirical constants, and X represents salinity, and found that the model accounted for 99%, 97%, 96%, 99%, and 96% of salt effect for cowpea shoot, leaf area, leaf dry weight, stem dry weight and root dry weight, respectively. We also found significant differences (P ≤ 0.05) of each biomass parameter among the 12 cultivars and obtained different sets of the empirical constants to quantitatively describe the response of each biomass parameter to salinity for individual cowpea cultivars. Since a significant salt × cultivar interaction effect (P ≤ 0.05) was found on leaf area and leaf dry weight, we concluded that salt tolerance differences exist among the tested cultivars.