Shoot Dry Matter Content Research Articles

Atividade biológica do solo cultivado com feijão-guandu sob diferentes manejos de adubação

ABSTRACT: Fertilization management of pigeon peas can increase soil quality and the N utilization by plants. Therefore, we evaluated the biological activity of soil cultivated with pigeon peas (Cajanus cajan (L) Millsp.) under different fertilization treatments. A randomized block design was used with three replicates and a 3×5 factorial arrangement (genotype×fertilization and inoculation management). At full flowering stage, the plants were collected and shoot dry matter was evaluated. Soil was sampled at 0-20 cm for various analysis viz. nodulation assessment; soil organic carbon; total nitrogen; carbon and nitrogen from microbial biomass; C/N ratio; β-glucosidase and urease enzymatic activity. Data were subjected to analysis of variance and Tukey’s test (P ≤ 0.05). A Pearson correlation matrix was constructed, and the similarity between treatments was evaluated using the Mahalanobis distance and grouping was done using the unweighted pair group method with arithmetic average (UPGMA). Both the experimental genotypes (BRS03 and BRS04) showed similar nodulation and shoot dry matter pattern with respect to fertilizer treatments. Furthermore, the microbial inoculation promoted a higher shoot dry matter content in all the genotypes. The application of mineral N and inoculation increased the total N content in the soil, favoring the mineralization of this nutrient. During the testing phase, the genotypes exhibited an increase in microbial carbon and microbial quotient levels, indicating an improvement in soil quality. The combination of fertilization and inoculation increased the enzymatic activity of β-glucosidase and urease. The correlation matrix showed a strong association between N total and C/N ratio. The formation of groups by UPGMA was observed as a function of inoculation, demonstrating its effect on soil biological variables.

Gradually increasing light intensity during the growth period increases dry weight production compared to constant or gradually decreasing light intensity in lettuce

The objective of this research was to investigate the effects of gradually increasing or decreasing photosynthetic photon flux density (PPFD) during cultivation compared to a constant PPFD on biomass production. Lettuce plants (Lactuca sativa L. ‘Expertise’) were grown in climate rooms in which every three days the PPFD was increased by 16 µmol m−2 s−1 (from 140 to 300 µmol m−2 s−1 from day 0 to 30), decreased (from 300 to 140 µmol m−2 s−1), or kept constant (221 µmol m−2 s−1), while the total light integral at the end of the cultivation period (30 d) was the same for all three treatments. Gradually increasing PPFD resulted in a 16 or 13% increase in total plant dry weight compared to treatments with decreasing or constant PPFD, respectively. This increase was explained by a higher light interception mainly because, in this treatment, most of the light was provided at the end of the cultivation period when the leaf area index was high. Consequently, the light use efficiency based on incident PPFD was highest when PPFD gradually increased, even though the light use efficiency based on intercepted PPFD was highest when PPFD gradually decreased during cultivation. Despite the higher shoot dry weight when PPFD gradually increased, shoot fresh weight was not significantly affected by the light treatments. This difference in response between fresh and dry weight resulted from a higher shoot dry matter content when PPFD gradually increased. Our results show that gradually increasing PPFD had a positive effect on dry weight accumulation and increased dry matter content, but did not affect the shelf life. So, although vertical farms enable growers to keep all conditions constant, some dynamic variation of conditions might be needed for optimizing the light use efficiency.

Rhizobacteria from Root Nodules of Brazilian Native Legumes Promote-Growth Sorghum bicolor L. Under Drought Conditions

ABSTRACT Plant growth-promoting bacteria (PGPB) are bacteria that can enhance protect native plants from abiotic stresses including drought. The inoculation of these PGPB into crop forage plants may increase productivity helping to suppress its growing demand in semiarid regions. The present paper aims to evaluate the Sorghum bicolor L. morphogenic characteristics and growth inoculated with native bacterial isolates from the Brazilian semiarid region under drought conditions. The endophytic bacteria isolated from root nodules of native leguminous plants named Mimosa tenuiflora (isolates – MTBV77, MTP78, MTBV12), Desmanthus pernambucanus (isolates – DPP1) and Mimosa caesalpiniifolia (isolate – MCLR34) were all presumably identified as rhizobia by performing the Polymerase Chain Reaction duplex amplification technique using primers that amplify the nifH and nodC genes. The seeds and roots of sorghum seedlings were inoculated with bacterial isolates. The plants were cultivated in pots under favorable water conditions (80% of the available water) and dry conditions (40% of the available water). The inoculation with bacterial isolates increased emission, elongation and length of the S. bicolor leaves, as well as increased its stem elongation, height, and shoot dry-matter content. However, the magnitude of the effects varied according to the imposed water regime. Thus, rhizobacteria from root nodules of Brazilian native legumes have the potential to promote plant growth. The bacterial isolates DPP1 and MTBV77 attenuate the effects of water stress and promote S. bicolor growth under drought conditions and are therefore promising for the use as an inoculant for S. bicolor sustainable cultivation to forage purposes.

Responses of intraspecific and interspecific variations of plant functional traits to grazing in degraded grassland

Understanding the responses of functional trait variation for grassland plants to grazing disturbance is highly helpful to clarify the community assembly mechanism, functional diversity maintenance, plant adaptation and their strategies. We investigated plant functional traits (plant height, root length, leaf area, root area, leaf dry matter content, shoot dry matter content, root dry matter content, specific leaf area, specific root length and root/ shoot ratio) and the responses of their variation characteristics to grazing disturbance in enclosure and grazing grasslands in Horqin Sandy Land. The results showed that the interspecific variation of functional trait was obviously higher than the intraspecific variation in degraded grassland. The relative contribution of interspecific variation to the overall trait variation ranged from 70.2% to 95.1%, while that of intraspecific variation only contributed 4.9% to 29.8%. However, that did not imply the intraspecific variation could be ignored in the community assembly. The interspecific variation in grazing grassland was lower than that in enclosed grassland, while the intraspecific variation increased but the interspecific variation decreased in grazing grassland. Grazing resulted in the decrease of leaf area and leaf dry matter content but the increase of specific root length for pastoral-resistant grasses. However, pastoral-tolerant forbs would improve their dominance in the community by decreasing specific root length and increa-sing leaf area and leaf dry matter content. The traits sensitive to grazing were leaf area, leaf dry matter content, specific root length, and specific leaf area. Leaf traits and root traits were significantly positively correlated within and with each other. Grazing would enhance the synergy of root traits while reduce the synergy of leaf traits. That meant grazing could change the trade-off strategy of functional traits in individual and population levels, and thus affect vegetation structure and function in community level.

Performance of cover crops under two irrigation regimes in the Coastal Tablelands region of Brazil

There is currently a lack of information regarding the performance of cover crops grown in the Coastal Tablelands region in the North of the Brazilian state of Espírito Santo, where zero tillage is increasingly being adopted. The objective of this study was to evaluate the agronomic performance of six cover crops (ruzi grass, jack bean, and the millets ADR 300, ADR 500, ADRf 6010, and BRS 1501) under two irrigation regimes. A field experiment setup was based on randomized blocks with split plots and four repetitions. Shoot dry matter content, plant height, leaf area, chlorophyll fluorescence, and root growth of the cover crops were evaluated. The irrigation regime influences the agronomic performance of most of the cover crops, with the exception of jack bean and ADRf 6010 millet, which were tolerant to water deficiency, based on our evaluations of the variables shoot dry matter, plant height, and leaf area. In terms of biomass production, ADRf 6010 millet is the most suitable crop for use in conservation systems under conditions of water stress in this region.

Plant Factories Are Heating Up: Hunting for the Best Combination of Light Intensity, Air Temperature and Root-Zone Temperature in Lettuce Production.

This study analyzed interactions among photon flux density (PPFD), air temperature, root-zone temperature for growth of lettuce with non-limiting water, nutrient, and CO2 concentration. We measured growth parameters in 48 combinations of a PPFD of 200, 400, and 750 μmol m–2 s–1 (16 h daylength), with air and root-zone temperatures of 20, 24, 28, and 32°C. Lettuce (Lactuca sativa cv. Batavia Othilie) was grown for four cycles (29 days after transplanting). Eight combinations with low root-zone (20 and 24°C), high air temperature (28 and 32°C) and high PPFD (400 and 750 μmol m–2 s–1) resulted in an excessive incidence of tip-burn and were not included in further analysis. Dry mass increased with increasing photon flux to a PPFD of 750 μmol m–2 s–1. The photon conversion efficiency (both dry and fresh weight) decreased with increasing photon flux: 29, 27, and 21 g FW shoot and 1.01, 0.87, and 0.76 g DW shoot per mol incident light at 200, 400, and 750 μmol m–2 s–1, respectively, averaged over all temperature combinations, following a concurrent decrease in specific leaf area (SLA). The highest efficiency was achieved at 200 μmol m–2 s–1, 24°C air temperature and 28°C root-zone temperature: 44 g FW and 1.23 g DW per mol incident light. The effect of air temperature on fresh yield was linked to all leaf expansion processes. SLA, shoot mass allocation and water content of leaves showed the same trend for air temperature with a maximum around 24°C. The effect of root temperature was less prominent with an optimum around 28°C in nearly all conditions. With this combination of temperatures, market size (fresh weight shoot = 250 g) was achieved in 26, 20, and 18 days, at 200, 400, and 750 μmol m–2 s–1, respectively, with a corresponding shoot dry matter content of 2.6, 3.8, and 4.2%. In conclusion, three factors determine the “optimal” PPFD: capital and operational costs of light intensity vs the value of reducing cropping time, and the market value of higher dry matter contents.

Liming and macronutrient on early growth of Eucalyptus benthamii

ABSTRACT: Macronutrient suppression is one way to identify which chemical elements is the most important in the early development of seedlings of forest species. This study evaluated the initial growth of Eucalyptus benthamii seedlings through morphological and physiological variables, submitted to doses of N, P and K, and liming. The experimental design to install the experiment was completely randomized, with a 2x9 factorial scheme, in which levels of factor “A” referred to absence and presence of liming and levels of factor “B”, to the different treatments of NPK. Morphological variables of SD (stem diameter) and H (height) and the physiological variables of A (photosynthesis), E (transpiration), gs (stomatal conductance), Ci/Ca (relationship between intercellular and atmospheric CO2 concentration) and WUE (water use efficiency) were measured. For morphological variables, the absence of N directly affected the means and there was a direct relationship between increase of the dose and increase of SD and H. There was a positive relationship of P mainly in relation to shoot dry matter content (SDMC) and root dry matter content (RDMC). For the physiological variables, there was no direct response with the doses of N or P, with K being the element that most influenced the variables, especially when limestone was applied, resulting in higher averages for photosynthesis, transpiration and stomatal conductance. With the purpose of meeting the morphological and physiological demands, the recommendation for cultivation of Eucalyptus benthamii under the conditions of this study is the doses 150-200-150, without liming application.

Induce of Plant Growth Regulators with and without Bio-fertilizer for Enhances the Adverse Effect of Salinity on Germination, Growth and Photosynthetic Pigments

This study aimed to explain the induce of plant growth regulators (ascorbic acid - AsA & salicylic acid - SA) in the presence or absence of bio-fertilizer (Acadian extract –ACE) for alleviated the effect of salinity stress on two cultivars of lettuce (Lactuca sativa, L. cv. Paris & cv. Royal). The lettuce seeds for four cultivars (cv. Paris Island Cos (cv. Paris) S1, cv. Royal S2, cv. Nader S3 & cv. Marvilli S4) soaked in PGRs (AsA, SA & GSH – 0.5 mM) and Acadian extract (ACE - 1%) for 12 hours in the dark at 4°C, for test of lettuce seeds viability (germination rate %). Germination both cultivars (cv. Paris S1 & cv. Royal S2) in trays of cork contains 218 eye for 14 days, transplanted the seedlings plant to plastic containers each pot containing one plant was irrigated with using NaCl salinity concentrations (0.00, 50; 100; 150 mM) 1st group alternative with distilled water and 2nd group alternating with ACE (1%), until harvest after 84 days. The results of germination indicated that the PGRs (AsA & SA) with both cultivars (cv. Paris S1 & cv. Royal S2) gives best results more the other PGRs (GSH) & bio-fertilizer (ACE) for the other cultivars. The data explained that the leaf number and leaf area, fresh and dry weights for shoot decreased significantly with increasing salinity concentrations compared with control, whereas the growth increased significantly more in cv. Royal S2 than in cv. Paris S1, particularly with AsA in the absence of bio-fertilizer (-ACE) more than SA compared with control. Whilst, the shoot succulence increased significantly with salinity concentrations more with AsA than SA especially in the absence of bio-fertilizer (-ACE) compared with control. However, the shoot dry matter content % decreased for both cultivars with increasing NaCl salinity concentrations especially with AsA more than SA in the absence (-ACE) compared with control. The evident recorded a significantly increased the photosynthetic pigments (Chl. a, Chl. b, carotenoids and total pigments) of leaves lettuce plant for both cultivars (cv. Paris & cv. Royal) with increasing NaCl salinity, also the photosynthetic pigments increasing more in cv. Royal S2 than in cv. Paris S1 especially with AsA more than SA in the absence (-ACE) under saline or non-saline conditions compared with the control. The data provide strong support to the hypothesis that exogenous application of AsA individually reduces the harmful effects of salinity and increases resistance to salinity in lettuce plant for both cultivars.

Phytotoxicity of Corncob Biochar before and after Heat Treatment and Washing

Biochar from crop residues such as corncobs can be used for soil amendment, but its negative effects have also been reported. This study aims to evaluate the phytotoxic effects of different biochar treatments and application rates on cress (Lepidium sativum). Corncob biochar was produced via slow pyrolysis without using purging gas. Biochar treatments included fresh biochar (FB), dried biochar (DB), washed biochar (WB), and biochar water extract (WE). Biochar application rates of 10, 20, and 30 t/ha were investigated. Significant phytotoxic effects of biochar were observed on germination rates, shoot length, fresh weight, and dry matter content, while severe toxic effects were identified in FB and WE treatments. Germination rate after 48 h (GR48) decreased with the increase of biochar application rates in all treatments. The observed order of performance of the biochar treatments for germination, shoot length, and shoot fresh weight for every biochar application rate was WB>DB>WE>FB, while it was the reverse order for the shoot dry matter content. WB treatment showed the best performance in reducing the phytotoxicity of biochar. The mitigation of the phytotoxicity in fresh corncob biochar by washing and heat treatment was found to be a simple and effective method.

Predicting individual plant performance in grasslands.

Plant functional traits are widely used to predict community productivity. However, they are rarely used to predict individual plant performance in grasslands. To assess the relative importance of traits compared to environment, we planted seedlings of 20 common grassland species as phytometers into existing grassland communities varying in land‐use intensity. After 1 year, we dug out the plants and assessed root, leaf, and aboveground biomass, to measure plant performance. Furthermore, we determined the functional traits of the phytometers and of all plants growing in their local neighborhood. Neighborhood impacts were analyzed by calculating community‐weighted means (CWM) and functional diversity (FD) of every measured trait. We used model selection to identify the most important predictors of individual plant performance, which included phytometer traits, environmental conditions (climate, soil conditions, and land‐use intensity), as well as CWM and FD of the local neighborhood. Using variance partitioning, we found that most variation in individual plant performance was explained by the traits of the individual phytometer plant, ranging between 19.30% and 44.73% for leaf and aboveground dry mass, respectively. Similarly, in a linear mixed effects model across all species, performance was best predicted by phytometer traits. Among all environmental variables, only including land‐use intensity improved model quality. The models were also improved by functional characteristics of the local neighborhood, such as CWM of leaf dry matter content, root calcium concentration, and root mass per volume as well as FD of leaf potassium and root magnesium concentration and shoot dry matter content. However, their relative effect sizes were much lower than those of the phytometer traits. Our study clearly showed that under realistic field conditions, the performance of an individual plant can be predicted satisfyingly by its functional traits, presumably because traits also capture most of environmental and neighborhood conditions.

Effects of tillage options on soil physical properties and cassava-dry-matter partitioning

Conservation tillage is efficient at reducing soil degradation, but affects soil physical properties, and leads to soil compaction, negatively impacting root production, and so it is rarely adopted by cassava cultivators. The objective of this study was to evaluate the dry-matter partitioning (DMP) during a full cassava season under different tillage methods. The effects of minimum tillage (MT), conventional tillage (CT) and no-tillage (NT) on soil water content, soil penetration resistance, macroporosity, microporosity and total porosity were evaluated at 70, 120, 230, 300 and 350 days after planting (DAP). Additionally, the DMP in cassava plants was evaluated every 30 days until 360 DAP at Botucatu, Brazil on an Alfisol soil. Our result revealed that the tillage type affected soil penetration resistance, macroporosity and total porosity as well as the dry matter content (DMC) on cassava leaf, stem, root and planted cutting. No significant difference was observed in total DMC. However, DMP differed significantly between 150 and 210 DAP, corresponding respectively to the root-thickening phase end and the dormancy phase beginning. The highest DMC of stem and planted cutting was observed in NT-developed plants. Shoot DMC was positively correlated with soil penetration resistance. CT and MT did not differ in root yield; hence, MT should be adopted instead of CT, as an effort to control soil erosion. NT increases the soil penetration resistance, and results in greater accumulation of DM in the stem and planted cutting than in the roots. Data suggest that increased soil penetration resistance under NT can decrease cassava root growth and induce the stem and planted cutting to play the role of storage organs.

English

In present study, a total of 104 bacteria and 96 actinomycetes were isolated from rhizosphere plant root of finger millet (Eleusine coracana) from Almora district of Uttarakhand, India. Isolates were characterized using microscopic and morphological methods followed by their biochemical test. Based on functional tests, four most promising isolates were identified using 23S rDNA primers as Streptomyces labedae (SB-9), Streptomyces flavofuscus (SA-11), and 16S rDNA primers as Pseudomonas poae (KA-5), and Pseudomonas fluorescens (KB-7). Influence of Glomus intraradices (G.I.) singly and along with actinomycetes and Pseudomonas spp. were evaluated under irrigated and water deficit conditions. Out of eight treatments studied in this study, a higher significant increase in plant height with S. labedae SB-9 + G.I and P. poae KA-5 + G.I were recorded. In well watered and water deficient conditions, maximum shoot dry matter content was recorded in P. Poae + P. flurosence + G.I and S. labedae + S. flavofuscus + G.I inoculated plants in comparison to their respective control. Under in vitro condition, P. poae KA-5 produced higher amount of indole acetic acid (IAA) among the selected isolates. Anti-oxidant enzyme, superoxide dismutase (SOD) and accumulation of free proline content in leaves were maximum in P. Poae + G.I inoculated plants under water deficit condition. In the presence of Streptomyces and Pseudomonas spp. a better mycorrhizal infection was observed in treated plant roots. This investigation support mutual symbiosis of Streptomyces and Pseudomonas strains with G. intraracides which had synergic effect on finger millet cv. Korchara plant under irrigated as well as under water stress condition. Key words: Glomus intraradices, Streptomyces, Pseudomonas, anti-oxidants, plant growth promotion, IAA production

Shoots, root and flowering time studies in chickpea (Cicer arietinum L.)<br>under two moisture regimes

The shoot and root behavior and flowering time of two chickpea genotypes (kabuli and desi types) was examined under well watered and moisture stress conditions in split drainpipes in 2006. The data on shoot and root fresh weight and dry weight and plant and soil moisture percentage were recorded at the late flowering stage. The observations on root and soil moisture were recorded at three depth level with gap of 15 cm each. The results revealed that both the plant types of chickpea behaved alike except for days to flower initiation which was significantly different in the two varieties. Root and Shoot fresh weights were significantly greater in well watered conditions, but on the other hand, there was no any significant effect of moisture stress on shoot dry matter content, suggesting that higher weight of fresh shoot was due to high uptake of water under well watered conditions which evaporated after drying. Fresh root weight was only significantly affected at 30 cm depth level due to varieties and 45 cm depth level due to treatments. The root moisture percentage was significantly affected at 15, 30 and 45 cm depth level due to varieties × treatments interaction, varieties and treatments, respectively. There found no significant difference in dry weight among the rooting depths. The cultivar Sheenghar-2000 retained higher root moisture content (7.57%) at 15 cm depth level under well watered.

Effect of Seed Source and Watering Intervals on Growth and Dry Matter Yield of Shea Butter Tree (<i>Vitellaria paradoxa</i> Gaertn F.) Seedlings

Shea butter tree seeds obtained from five locations in Guinea and Sudan savanna zones of Nigeria were evaluated for seedling growth under three watering intervals. The accessions were named after the site of collection, which included Makurdi, Minna, Jalingo, Yola and Kano while the watering intervals included 3, 6, and 9 day-intervals. Factorial combinations of the accessions and the watering intervals were laid out in a completely randomized design (CRD) replicated three times. Data on growth pattern, dry matter yield and distribution were collected between July 2006 and April 2007. Result indicated that accession had significant (P < 0.05) effect on all traits except number of leaves, total shoot length, shoot dry matter content and dry matter distribution to the roots and leaves. Watering intervals exerted significant effect only on fresh weight of roots, total fresh weight of seedling, root dry weight, leaf dry weight, total plant dry weight, and per cent total dry matter. Generally, the Jalingo accession was superior in most seedling attributes while Makurdi was the most inferior, a pattern probably associated with heavier seed weight of Jalingo and light seeds from Makurdi used for planting. The interaction between accession and watering intervals was significant (P < 0.05) on most characters except seedling girth, total shoot length, fresh weight of shoot, dry matter distribution to the root and per cent total dry matter. Dry matter content of the leaves and roots varied significantly (P < 0.05) with seedlings from the Makurdi seed source giving the lowest values. Amount of dry matter allocated to the roots was more than 70% in all the accessions. Generally, the longest watering interval produced seedlings with the longest roots. The Kano accession appeared more tolerant to water stress judging mainly from its dry weight/matter traits. On the other hand, the Minna provenance performed better under the 3 and 6 days watering intervals. Other accessions performed more or less uniformly under all watering intervals Keywords: Shea butter tree seeds, Accession, Watering intervals, Seedling growth, Dry matterBio-Research Vol. 6 (1) 2008: pp. 303-307

Genetic mapping of natural variation in potassium concentrations in shoots of Arabidopsis thaliana

Naturally-occurring variation in K(+) concentrations between plant genotypes is potentially exploitable in a number of ways, including altering the relationship between K(+) accumulation and growth, enhancing salinity resistance, or improving forage quality. However, achieving these requires greater insight into the genetic basis of the variation in tissue K(+) concentrations. To this end, K(+) concentrations were measured in the shoots of 70 Arabidopsis thaliana accessions and a Cape Verdi Island/Landsberg erecta recombinant inbred line (RIL) population. The shoot K(+) concentrations expressed on the basis of fresh matter (KFM) or dry matter (KDM) were both broadly and normally distributed as was the shoot dry matter content per unit fresh weight (DMC). Using the data from the RILs, four quantitative trait loci (QTL) were identified for KFM and three for KDM. These were located on chromosomes 2, 3, 4, and 5. Two of the QTLs for KFM overlapped with those for KDM. None of these QTLs overlapped with those for fresh weight or dry weight, but the QTL for KDM located on chromosome 3 overlapped with one for DMC. In silico analysis was used to identify known or putative K(+) and cation transporter genes whose loci overlapped with the QTLs. In most cases, multiple genes were identified and the possible role of their gene products in determining shoot K(+) concentrations is discussed.

Short communication : Phosphorus and nitrogen fertilization in sweet corn (Zea mays L. var. saccharata Bailey)

To evaluate the effect of combining different levels of P and N fertilisation on yield and uniformity of a sweet corncrop hybrid Freshy, a factorial trial combining three levels of N (0, 100 and 200 kg of N ha-1) and three levels of P (0,40 and 80 kg of P2O5 ha-1) was carried out. Total leaf number, height up to ear insertion, leaf width and length, leaf area,plant height, stem diameter, biomass production, shoot dry matter content, harvest index and yield with and withouthusk, husk proportion and ear diameter were measured. Significant differences in leaf width and length, leaf area, plantheight, ear diameter, biomass production and yield with and without husk were observed with N fertilisation. On theother hand, significant differences in leaf length, unit leaf area, ear diameter and biomass production were observedwith P fertilisation. A N x P interaction was only observed for shoot dry matter content

Influence of nutrient solution concentration and a root pathogen ( Pythium aphanidermatum) on tomato root growth and morphology

Young roots, especially those in the root hair zone, are most important for nutrient uptake. However, these roots are also sensitive to high nutrient solution concentration and root pathogens, major problems in soilless culture systems. Supply of nutrient solution at a constant electrical conductivity (EC) can increase the EC in the root environment up to 10 dS m −1. Pythiaceae are among the most important root pathogens in soilless systems. Therefore, investigations were carried out to quantify and compare root damage by high nutrient solution EC and by Pythium aphanidermatum (Edson) Fitzp. Three tomato plants at two-leaf-stage ( Lycopersicon esculentum [Mill] L. cv. Counter) were transferred to a 2 l container filled with aerated nutrient solution. They grew in climate chambers for 14 days (16 h light 600 μmol m −2 s −1, 30/25 °C day/night). In one experiment, a basic nutrient solution of 1.5 dS m −1 was supplemented with either NaCl or macronutrients to give an EC of 1.5, 5 or 9 dS m −1. In another experiment, plants were inoculated with P. aphanidermatum (0, 10 2, or 10 4 oospores ml −1 solution). All treatments were replicated five and four times, respectively. On days 3, 7, 10, and 13 after treatment one plant was sampled from each container. Fresh and dry mass of shoots and roots, total root length, number of adventitious roots and of all tap root laterals decreased with increasing nutrient solution EC. Dry matter content of roots and tap root diameter were not influenced while shoot dry matter content increased with increasing EC. NaCl enhanced root fresh matter, tap root diameter, total root length and number of adventitious roots compared with the macronutrient treatment. On the contrary shoot dry matter content and number of all laterals were reduced by NaCl. Three days after inoculation with P. aphanidermatum the number and length of roots were reduced significantly by the treatment 10 4 oospores ml −1. P. aphanidermatum effects were greatest on young and thin roots, particularly those of the second and third laterals. Reduction increased with time and increasing number of inoculated oospores. Root diameters were greatest in the treatment with 10 4 oospores ml −1. Results confirm that attempts to extrapolate results obtained on average root systems to single root formation could be misleading. Furthermore, a tomato plant can compensate to some extent its water uptake of a root system reduced by nutrition or pathogen effects.

Produção de alface em função de cultivares e tipos de tela de sombreamento nas condições de Mossoró

Conduziram-se dois experimentos na horta do Departamento de Fitotecnia da ESAM, no período de outubro de 1999 a janeiro de 2000. O objetivo do primeiro experimento foi avaliar o desempenho de três cultivares de alface sombreadas por três tipos de tela e o do segundo, comparar a produtividade da alface sob os três tipos de tela de sombreamento com a do cultivo a céu aberto. O delineamento experimental utilizado, em ambos os experimentos, foi de blocos casualizados completos. No primeiro experimento, os tratamentos resultaram de um fatorial 3 x 3, provenientes da combinação dos três tipos de tela de sombreamento (branca e verde, com malha de 2 x 2 mm, e preta com malha irregular) e três cultivares de alface (Great Lakes, Verônica e Regina), com quatro repetições. No segundo experimento, os tratamentos provieram dos três tipos de tela de sombreamento e do cultivo da alface, cultivar Verônica a céu aberto, com três repetições. O espaçamento utilizado em ambos os experimentos foi de 0,20 x 0,20 m. As características avaliadas foram altura e diâmetro de plantas, número de folhas por planta, massa seca da parte aérea, produtividade, taxa de crescimento relativo, ganho de produtividade, rendas bruta e líquida e taxa de retorno. A altura de plantas foi afetada pela interação tipos de tela de sombreamento e cultivares. O diâmetro de planta e o número de folhas por planta foram influenciados apenas pelas cultivares. O teor de massa seca e a produtividade foram influenciados pelos tipos de tela de sombreamento e cultivares. A utilização de tela de cor branca associada com a cultivar Great Lakes na fase de muda constituiu-se em melhor taxa de retorno por Real investido, e numa tecnologia para incrementar a rentabilidade do produtor na região semi-árida do Nordeste brasileiro.

Effect of Temperature on the Growth and Development of Tomato Fruits

Tomato fruits ripened 95, 65, 46 and 42d after flower opening when plants were grown under controlled environmental conditions at 14, 18, 22 and 26°C, respectively. A similar response to temperature was observed when the temperature of individual trusses was modified while the plants were grown at 20°C. These data were used to develop a thermal time model for fruit maturation. However, when buds/fruits were heated at different stages in their development, the thermal time model proved to be a poor predictor of the time of ripening. Fruits were more sensitive to elevated temperature in their later stages of maturation. Temperature also affected the rates of fruit growth in volume; these could be adequately described using a Gompertz function. Low temperatures reduced absolute volume growth rates and delayed the time at which the absolute growth rate became maximal. However, the response of fruit growth to temperature differed when only the temperature of the fruits was modified. There was a tendency towards small parthenocarpic fruits at both high (26°C) and low (14°C) temperature regimes which, combined with low flower numbers and poor fruit set at 26°C, resulted in low fruit yields. Temperature also affected the shoot dry matter content and partitioning.

Seedling growth and leaf surface morphological responses of three rangeland weeds to ultraviolet-B radiation

The influence of ultraviolet-B (UV-B) radiation on seedling growth and leaf surface characteristics of important rangeland weedsCynoglossum officinaleL. (houndstongue),Centaurea diffusaLam. (diffuse knapweed), andTragopogon pratensisL. (meadow salsify) was investigated in a greenhouse by exposing seedlings to 0, 7, or 11 kJ m−2d−1of biologically effective UV-B radiation. UV-B radiation reduced leaf, stem, and root fresh weights, leaf area, and leaf: shoot ratio and increased shoot dry matter content, specific leaf weight, and leaf greenness ofC. officinaleseedlings. Leaf, stem, and root fresh weight, and leaf area ofC. diffusaseedlings decreased, whereas shoot dry matter content, specific leaf weight, leaf: shoot ratio, and leaf greenness were unaffected.T. pratensisseedlings exposed to UV-B radiation had diminished leaf greenness, but no change was observed in leaf or stem fresh weight, leaf area, or leaf: shoot ratio. Uniseriate trichome abundance inC. officinaleseedlings increased and trichome orientation changed in response to UV-B exposure. UV-B treatments decreased uniseriate trichome abundance inC. diffusa; glandular trichome abundance and the ratio of glandular: uniseriate trichomes were not affected.T. pratensisseedlings showed no change in the amount of epicuticular wax on the adaxial leaf surface in response to UV-B irradiation. Shoot dry weight was not influenced by removal of epicuticular wax prior to UV-B exposure. Results suggest that epicuticular wax is not an important factor in acclimation ofT. pratensisseedlings to UV-B radiation. Susceptibility to UV-B–induced damage was greatest forC. officinaleseedlings and least forT. pratensisseedlings. Modification of plant morphology or reduction in growth induced by enhanced UV-B radiation may influence competitive relationships between rangeland weeds and their associated forage species.