Root Dry Matter Production Research Articles

Subproduto da indústria de alumínio como amenizante de solos contaminados com cádmio e chumbo

A poluição do solo com elementos-traço tem sido motivo de preocupação nos últimos anos, o que justifica melhor conhecimento da disponibilidade desses elementos no ambiente, visando amenizar seus efeitos em áreas contaminadas. Este trabalho teve como objetivo avaliar o desempenho de um subproduto da indústria de alumínio como amenizante de solos contaminados com Cd e Pb. Foram utilizados um Neossolo Quartzarênico (930 g kg-1 de areia, 20 g kg-1 de silte e 50 g kg-1 de argila) e um Latossolo Vermelho (360 g kg-1 de areia, 100 g kg-1 de silte e 540 g kg-1 de argila) contendo 15 % de solo contaminado com Cd e Pb. Foram feitas cinco repetições testando-se o efeito da aplicação do subproduto in natura a 0; 0,25; 0,50; 1,00; e 2,00 %. Para comparação, utilizaram-se calcário, silicato e turfa a 0,25; 0,50; e 2,00 %, respectivamente, e cada um dos solos sem contaminação. Cultivou-se B. decumbens, fazendo coletas de lixiviado e determinando o pH e a CE. As concentrações de Cd e Pb foram avaliadas no lixiviado não-filtrado e filtrado (0,45 µm). Avaliaram-se a produção de matéria seca de raízes (MSR) e da parte aérea (MSPA) e as quantidades de Cd e Pb em ambas após digestão nitroperclórica. Os amenizantes contribuíram para aumentar o pH dos lixiviados do Neossolo Quartzarênico e do Latossolo Vermelho, tendo este último apresentado menores valores de condutividade eletrolítica quando comparado ao primeiro. Os teores de Cd nos lixiviados filtrados (fração solúvel) foram os mesmos dos lixiviados não-filtrados, enquanto os de Pb apresentaram diferenças. As produções de MSR e MSPA aumentaram com o aumento das taxas de aplicação do subproduto, e a quantidade de Cd na MSPA da B. decumbens foi maior que a de Pb.

Produção e valor nutritivo do capim-tanzânia fertilizado com nitrogênio e fósforo

O experimento foi realizado em casa de vegetação com o objetivo de avaliar o efeito da adubação nitrogenada e fosfatada sobre a produção de matéria seca (MS) da parte aérea e das raízes, o teor e a produção de proteína bruta (PB) e de fibra em detergente neutro (FDN). Utilizou-se o delineamento experimental inteiramente casualizado em esquema fatorial 4 × 2, composto de quatro doses de nitrogênio (0, 50, 100 e 150 mg/dm³) e duas doses de P2O5 (0 e 45 mg/dm³) com quatro repetições. As sementes da gramínea foram estabelecidas em vasos com capacidade de 6,3 L, de modo que, após desbaste, permaneceram três plantas por vaso. Observou-se interação entre doses de nitrogênio e a produção de MS da parte aérea e de raízes. As produções estimadas de MS da parte aérea obtidas com associação de nitrogênio (0, 50, 100 e 150 mg/dm³) e P2O5 (45 mg/dm³) foram de 4,7; 18,5; 32,3 e 46,1 g/vaso e a produção de MS de raízes, de 6,3; 41,7; 77,1 e 112,5 g/vaso, respectivamente. As doses de nitrogênio e fósforo não influenciaram o teor de FDN, mas afetaram o de PB, que foi maior nas doses mais altas de nitrogênio sem adição de fósforo. A adubação com doses crescentes de nitrogênio associadas a P2O5 aumenta a produção e o valor nutritivo do capim-tanzânia.

Inoculação de Azospirillum amazonense em dois genótipos de milho sob diferentes regimes de nitrogênio

A adaptabilidade de genótipos de milho a ambientes onde os nutrientes não estejam prontamente disponíveis pode ser relacionada com a adaptação à predominância, nos solos, das formas de N nítrica e amoniacal e à associação com microrganismos benéficos como as bactérias diazotróficas e, ou, promotoras de crescimento de plantas. O objetivo deste trabalho foi verificar o comportamento de dois híbridos intervarietais de milho sob diferentes doses e formas de N, assim como o efeito da inoculação com Azospirillum amazonense, em um ensaio em casa de vegetação, utilizando vasos preenchidos com vermiculita e solução nutritiva de Hoagland como fonte de nutrientes. O delineamento experimental foi de blocos ao acaso em esquema fatorial, constituindo os tratamentos em: dois híbridos intervarietais, H1 (Carioca x Eldorado) e H2 (Palha Roxa ES x Sol da Manhã); plantas inoculadas ou não inoculadas com A. amazonense, e três regimes de N, conforme doses e proporções seguintes: 126 mg semana-1 de N (75 % NH4+ : 25 % NO3-); 126 mg semana-1 de N (25 % NH4+ : 75 % NO3-), e 12,6 mg semana-1 de N (50 % NH4+ : 50 % NO3-). Vinte e cinco dias após o plantio, as plantas foram separadas em raiz e parte aérea para determinação da matéria seca, conteúdos totais de N e P, atividade das enzimas nitrato redutase e glutamina sintetase e açúcares solúveis totais. O híbrido H1, mais eficiente em avaliações preliminares em campo, produziu mais matéria seca e apresentou maior eficiência na utilização de N e P. Plantas que receberam a maior dose de N, independentemente do predomínio da forma nítrica ou amoniacal, apresentaram maior acúmulo de N (nas raízes e parte aérea) e P (na parte aérea) e maior índice de utilização de P. Com o predomínio da forma amoniacal, observou-se incremento na produção de matéria seca da parte aérea e na atividade da glutamina sintetase, bem como decréscimo na concentração de açúcares solúveis totais nas raízes. A inoculação com A. amazonense promoveu maior produção de matéria seca e acúmulo de N nas raízes.

Uptake, Subcellular Distribution, and Chemical Forms of Cadmium in Wild-Type and Mutant Rice

Wild-type (Zhonghua 11) and mutant rice ( Oryza sativa L.) plants were used to investigate the efiect of cadmium (Cd) application on biomass production, to characterize the influx of Cd from roots to shoots, and to determine the form, content, and subcellular distribution of Cd in the roots, leaf sheaths, and leaves of the rice plants. Seedlings were cultivated in a nutrient solution and were treated with 0.5 mmol L −1 of Cd 2+ for 14 d. The sensitivity of rice plants to Cd toxicity was tested by studying the changes in biomass production and by observing the onset of toxicity symptoms in the plants. Both the wild-type and mutant rice plants developed symptoms of Cd stress. In addition, Cd application signiflcantly ( P ≤ 0.01) decreased dry matter production of roots, leaf sheaths, and leaves of both types, especially the mutant. The Cd content in roots of the mutant was signiflcantly ( P ≤ 0.05) higher than that of the wild-type rice. However, there was no signiflcant difierence in the Cd content of roots, leaf sheaths, and leaves between the wild-type and mutant rice. Most of the Cd was bound to the cell wall of the roots, leaf sheaths, and leaves, and the mutant had greater Cd content in cell organelles than the wild type. The uneven subcellular distribution could be responsible for the Cd sensitivity of the mutant rice. Furthermore, difierent chemical forms of Cd were found to occur in the roots, leaf sheaths, and leaves of both types of rice plants. Ethanol-, water-, and NaCl-extractable Cd had greater toxicity than the other forms of Cd and induced stunted growth and chlorosis in the plants. The high Cd content of the toxic forms of Cd in the cell organelles could seriously damage the cells and the metabolic processes in mutant rice plants.

Influência de diferentes doses de corretivo e de camadas de correção da acidez de um neossolo litólico distrófico na produção de matéria seca de milho

The effects of different bases saturation values and corrected layers of soil acidity on dry matter production of maize plants were studied under controlled conditions. With the increase of lime doses, the values of pH (CaCl 2 ) and base saturation were increased. On the other hand, the exchangeable aluminum values were reduced. The values of shoot and roots dry matter production were significantly higher then the control. The increases of deep correction layers resulted in an increase of dry matter production of maize plants. On the other hand, for the same correction layer, the values of dry matter production was not significantly different between the bases saturation treatments. Even though the maize plants have presented a positive answer to liming, the values of bases saturation higher than 40% did not significantly increase dry matter production of maize plants

Nutrição mineral do mangarito num Latossolo Vermelho Amarelo

Com o objetivo de caracterizar as limitações nutricionais para a produção de matéria seca do mangarito [(Xanthosoma mafaffa (L.) Schott)], conduziu-se um experimento em casa de vegetação com amostras da camada de 0-20 cm de um Latossolo Vermelho Amarelo sob vegetação de cerrado, coletado no município de Montes Claros, MG. O cultivo foi realizado em vasos de 3 L de capacidade. O delineamento experimental foi inteiramente casualizado, em treze tratamentos, com três repetições. Os tratamentos foram baseados na técnica do elemento faltante (em que se omite a calagem e cada um dos macronutrientes e micronutrientes). A ordem decrescente dos tratamentos que mais afetaram a produção de matéria seca da parte aérea foi: -Calagem> -P > -S > testemunha > -B > -Calagem+Ca+Mg > -N > -K. A omissão de Ca, Mg, Zn e Cu não afetaram a produção de matéria seca da parte aérea. A ordem decrescente dos tratamentos que mais afetaram a produção de matéria seca de raízes foi: -B > -Mg > -Calagem+Ca+Mg > -K > -N > -Zn > -Calagem > -S > -Cu > -Ca > -Cu > -Ca > testemunha > -P.

Root growth, aerenchyma development, and oxygen transport in rice genotypes subjected to drought and waterlogging

Soils under field conditions may experience fluctuating soil water regimes ranging from drought to waterlogging. The inability of roots to acclimate to such changes in soil water regimes may result in reduced growth and function thereby, dry matter production. This study compared the root and shoot growth, root aerenchyma development, and associated root oxygen transport of aerobic and irrigated lowland rice genotypes grown under well-watered (control), waterlogged, and droughted soil conditions for 30 days. The aerobic genotypes were as tolerant as the irrigated lowland genotypes under waterlogging because of their comparable abilities to enhance aerenchyma that effectively facilitated O 2 diffusion to the roots for maintaining root growth and dry matter production. Under drought, aerobic genotypes were more tolerant than the irrigated lowland genotypes due to their higher ability to maintain nodal root production, elongation, and branching, thus, less reduction in dry matter production. Aerenchyma was also formed in droughted roots regardless of genotypes, but was resistant to internal O 2 transport under O 2 deficiency. The ability of roots to resist temporal variations in drought and waterlogging stresses might have strong implications for the adaptation of rice growing in environments with fluctuating soil water regimes.

Root-invading fungi of milk vetch on the Loess Plateau, China

Root-invading fungi of milk vetch ( Astragalus adsurgens) at different growth stages grown in three ages of sown pasture soil were studied in Huanxian county, Gansu province, China. Pathogenicity was tested by seed and soil inoculation. A total of 44 fungi were isolated from milk vetch roots, 32 from the roots of field plants and 37 from the roots of potted seedlings. The total percentage of root segments yielding fungal colonies increased with age of plants; they were 70.5%, 82.3% and 97.8% in 1-, 3-, and 5-year-old plant roots, respectively, differences that were significant ( P < 0.05). The frequency of isolation from roots of plants at re-greening, branching, flowering and yellowing growth stages were 62.0%, 95.3%, 93.0% and 83.7%, respectively. The total percentage of root segments yielding fungal colonies from 3-, 6- and 12-week-old potted seedlings were 21.8%, 44.7% and 32.0%, respectively, differences that were also significant ( P < 0.05). Seedlings were easily infected and symptoms of damping-off disease were common in seedlings younger than 3-week-old. Of the 44 fungi isolated and tested for pathogenicity by seed inoculation, 19 decreased seed germination rate, 12 decreased seedling shoot length, and 22 decreased seedling root length. Fusarium solani, F. oxysporum, F. chlamydosporum, F. avenaceum and Gliocladium roseum were strongly pathogenic to milk vetch. In soil inoculation tests, these same fungi (except for F. chlamydosporum) decreased seedling root dry matter production significantly ( P < 0.05), but seed germination and seedling survival were not affected by any of these fungi.

Silicon Requirement of Coarse and Fine Varieties of Rice

ABSTRACT Silicon (Si) provides extra strength to plants against lodging. A hydroponic study was conducted to compare Si requirements of three high yielding, nitrogen (N) responsive, coarse varieties of rice (KSK-133, PK-3717-12, and IRRI-6) with four low yielding, lodging susceptible, fine varieties of rice (BAS-191, BAS-385, BAS-370, and PK-3300). Two-week-old uniform seedlings were grown in half strength Johnson's nutrient solution containing 0, 25, 75, and 150 mg Si kg− 1 as sodium silicate. The plants were allowed to grow for 45 days after transplanting. Silicon application significantly (P ≤ 0.01) increased root and shoot dry matter production in all the rice varieties. The maximum shoot dry matter production occurred at 75 mg Si kg−1 and decreased uniformly in all the rice varieties at 150 mg Si kg− 1. However, growth response to Si application varied significantly (P ≤ 0.01) among various rice varieties. Root: shoot growth ratio, varying from 0.11 to 0.15, did not follow any trend. Different rice varieties and Si addition had a significant (P ≤ 0.01) main and interactive effect on concentration and total uptake of Si in rice root and shoot. Relative increases in Si content, both in shoot and root, were gradual and several fold with increasing rates of Si application. The effect was more pronounced in Basmati varieties (BAS-198, BAS-385, and BAS-370) than other varieties. A 0.91 mg Si g− 1 plant tissue was optimum for growth of KSK-133 (coarse), which was significantly higher than the optimum level, 0.62 mg Si g− 1 plant tissue, for Bas-370 (fine). However, further verification of the results is warranted under field situation.

Foliar-Applied Glyphosate Substantially Reduced Uptake and Transport of Iron and Manganese in Sunflower (Helianthus annuus L.) Plants

Evidence clearly shows that cationic micronutrients in spray solutions reduce the herbicidal effectiveness of glyphosate for weed control due to the formation of metal-glyphosate complexes. The formation of these glyphosate-metal complexes in plant tissue may also impair micronutrient nutrition of nontarget plants when exposed to glyphosate drift or glyphosate residues in soil. In the present study, the effects of simulated glyphosate drift on plant growth and uptake, translocation, and accumulation (tissue concentration) of iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) were investigated in sunflower (Helianthus annuus L.) plants grown in nutrient solution under controlled environmental conditions. Glyphosate was sprayed on plant shoots at different rates between 1.25 and 6.0% of the recommended dosage (i.e., 0.39 and 1.89 mM glyphosate isopropylamine salt). Glyphosate applications significantly decreased root and shoot dry matter production and chlorophyll concentrations of young leaves and shoot tips. The basal parts of the youngest leaves and shoot tips were severely chlorotic. These effects became apparent within 48 h after the glyphosate spray. Glyphosate also caused substantial decreases in leaf concentration of Fe and Mn while the concentration of Zn and Cu was less affected. In short-term uptake experiments with radiolabeled Fe (59Fe), Mn (54Mn), and Zn (65Zn), root uptake of 59Fe and 54Mn was significantly reduced in 12 and 24 h after application of 6% of the recommended dosage of glyphosate, respectively. Glyphosate resulted in almost complete inhibition of root-to-shoot translocation of 59Fe within 12 h and 54Mn within 24 h after application. These results suggest that glyphosate residues or drift may result in severe impairments in Fe and Mn nutrition of nontarget plants, possibly due to the formation of poorly soluble glyphosate-metal complexes in plant tissues and/or rhizosphere interactions.

Short-term Responses of Soil C and N Fractions to Tall Fescue Endophyte Infection

Tall fescue (Festuca arundinacea Schreb.) is naturally infected with a fungal endophyte, Neotyphodium coenophialum, which produces toxic ergot alkaloids that negatively affect herbivores and that may alter soil organic matter dynamics. A 60-week mesocosm study with a factorial arrangement of soil type (clay loam and loamy sand) and endophyte infection (with and without) was conducted to determine potential changes in soil C and N fractions. Forage and root dry-matter production were greater with than without endophyte infection, while forage C and N concentrations were unaffected. Total, particulate, mineralizable, and aggregate-associated C and N fractions increased several fold during the course of the experiment due to large rhizosphere inputs in all treatments. The fraction of total C and N in water-stable macroaggregates (>0.25 mm) was initially 0.43±0.10 and 0.46±0.16, respectively, and increased during the course of the experiment to 0.68±0.06 and 0.56±0.15 when averaged across soil type and endophyte infection level as a result of organic matter cycling and deposition in this active biophysical fraction. Changes in soil C and N fractions due to endophyte infection were minimal. The lack of detectable changes in soil C and N fractions due to endophyte infection may have been a result of the overwhelming input of C from roots and/or the relatively short-term nature (60 weeks). Greater plant productivity of endophyte-infected tall fescue is likely a contributing mechanism for eventual changes in total and active C and N fractions that have been observed in long-term pastures. Abbreviations: E) – endophyte free; E+ – endophyte infected

Fine root dynamics in a Japanese cedar ( Cryptomeria japonica) plantation throughout the growing season

To elucidate the dynamics of fine roots and root tips, which are key components in water and nutrient uptake by plants, sequential soil coring was conducted in a 28-year-old Japanese cedar ( Cryptomeria japonica) plantation in the northern part of the Kanto plain, Japan. Biomass, necromass, and the number of white and brown root tips of fine roots <1 mm in diameter were determined every 6 weeks from early March to mid-November 2004. The production and mortality of fine roots and their tips between sampling periods were also estimated. Fine root mass and the number of root tips were largest in the uppermost soil layer and showed seasonal changes. Fine root biomass increased until late summer (August) and then declined, while necromass was lower in summer than in other seasons. The largest number of white root tips was observed in early summer (June) and in autumn (October) at a soil depth of 0–15 and 15–35 cm, respectively. The number of brown root tips was greater in late summer to autumn (August–October) than during other sampling periods. These results suggest that Japanese cedar has a high potential for water and nutrient uptake in summer, although the potential in autumn may also be considerable. The production of fine root dry matter peaked in summer (June–August), except in the lowest soil layer (25–35 cm deep). The production of white root tips in topsoil also reached a peak in mid-summer (July–August), whereas seasonal variation was unclear in deeper soil. Fine root production in the topsoil ceased during the early summer (June–July), probably due to drought stress or to the predominant allocation of carbon into aboveground organs. The mortality rates of fine roots were low until late summer (March–August), but sharply increased thereafter (August–November). Thus, the production and mortality of fine roots of Japanese cedar show clear seasonal changes. Soil depth, appears to strongly affect seasonal dynamics, suggesting that external conditions, such as soil temperature and moisture, together with the physiological status of the trees, substantially influence the fine-root dynamics of Japanese cedar.

Germination and initial growth of guava plants irrigated with saline water

The present study was carried in order to evaluate the effect of saline water irrigation with electrical conductivity (ECw) of 0.5; 1.5; 3.0; 4.5 and 6.0 dS m-1, on germination and some growth variables during the seedling formation process of four guava cultivars (Psidium guajava L.): Pentecoste, Paluma, Surubim and IPA B-38. Water salinity inhibited the germination process, plant height, stem diameter, leaf area and dry matter production of roots, stems and leaves, independently of cultivar. After germination, the seedlings did not survive due to saline water effects of ECw 4.5 and 6.0 dS m-1. After 180 days of sowing, the seedlings irrigated with ECw more than 1.5 dS m-1 did not present agronomic quality for planting. Dry matter production sequence of different parts of plants was as follows: leaves &gt; roots &gt; stems, without significant differences among cultivars especially when irrigated with saline water of ECw &gt; 3.0 dS m-1.

The effects of salinity and soil drying on nutrient uptake and growth of Spartina alterniflora in a simulated tidal system

A study quantifying the role of the interactive effects of salinity and soil drying on nutrient uptake in Spartina alterniflora was conducted in a climate-controlled greenhouse. The experiment consisted of three levels of salinity (3–5 g/L, L; 15–20 g/L, M; 35–38 g/L, H) as well as three dynamic water levels: drought (water level maintained at least 20 cm below the soil surface at high tide, D), intermediate soil drying (water level maintained between 20 cm below the soil surface at low tide and 10 cm below the soil surface at high tide, I), and flooding (water level maintained 3–5 cm above the soil surface at high tide and 10 cm below the soil surface at low tide, F). Survival, shoot and root dry matter production, and concentrations of Al, Ca, Fe, Mg, N, P, K, Na, and S were measured along with soil conditions of redox potential and water potential. Contrary to expectations, the interactive effects of salinity and soil drying were not additive on plant nutrient uptake or biomass. However, both salinity and soil drying significantly impacted root and shoot dry weights. In addition, significant decreases were seen in all nutrients in response to increases in salinity and/or soil drying. High salinity in conjunction with drought (HD) decreased survival to 71%, whereas survival was 100% for all other treatments. Furthermore, leaf chlorosis and browning occurred in plants under increased salinity and drought conditions (HD and MD). Therefore, it appears that drought may magnify the adverse effects of salinity on plant nutrient status. Although the combined effects of increased salinity and soil drying did not appear to be detrimental to this species, significant decreases in nutrient uptake seen in response to the combined effects at severe levels (HD), if continued over an extended period, may be detrimental enough to cause large-scale marsh browning as noted in the field.

Aluminium-phosphorus interactions on growth and some physiological traits of carrot and radish plants

aluminium treatment caused a significant decrease in root length and dry matter yield in the shoots and roots of carrot (Daucus carotaL.) and radish (Raphanus sativusL.) plants. this reduction was concomitant with a decrease in the accumulation of soluble sugars and total amino acids, whereas a significant increase in the proline content of the shoots and roots was detected. Soluble protein remained more or less unchanged when Al was applied at low and moderate levels. However, at higher Al levels, the losses in soluble sugars were accompanied by increases in soluble protein in radish, whereas in carrot the opposite effect was observed. The application of phosphorus fertilizer to al-treated plants counteracted the toxic effect of aluminium by increasing root elongation and dry matter production. This was associated with high contents of soluble sugars and soluble protein as well as ca, mg and p, especially at low and moderate levels of aluminium

How do plants achieve tolerance to phosphorus deficiency? Small causes with big effects.

Genotypic differences in phosphorus (P) uptake from P-deficient soils may be due to higher root growth or higher external root efficiency (micrograms of P taken up per square centimeter of root surface area). Both factors are highly interrelated because any additional P provided by externally efficient roots will also stimulate root growth. It will be necessary to separate both factors to identify a primary mechanism to formulate hypotheses on pathways and genes causing genotypic differences in P uptake. For this purpose, a plant growth model was developed for rice (Oryza sativa) grown under highly P-deficient conditions. Model simulations showed that small changes in root growth-related parameters had big effects on P uptake. Increasing root fineness or the internal efficiency for root dry matter production (dry matter accumulated per unit P distributed to roots) by 22% was sufficient to increase P uptake by a factor of three. That same effect could be achieved by a 33% increase in external root efficiency. However, the direct effect of increasing external root efficiency accounted for little over 10% of the 3-fold increase in P uptake. The remaining 90% was due to enhanced root growth as a result of higher P uptake per unit root size. These results demonstrate that large genotypic differences in P uptake from a P-deficient soil can be caused by rather small changes in tolerance mechanisms. Such changes will be particularly difficult to detect for external efficiency because they are likely overshadowed by secondary root growth effects.

Seleção de genótipos de alface eficientes na absorção do fósforo

Nineteen late flowering lettuce genotypes from the UENF horticultural germoplasm bank were evaluated for phosphorus utilization efficiency under a 10 mg.dm -3 P level. A biometrical analysis of genetic parameters and genetic, phenotypic and environment correlations between shoot and root dry matter production, P content in roots and shoot Puptake, P-translocation and P utilization efficiency was undertaken. Genetic variability, which could be promising to obtain positive response to selection, was identified. Highest genotypic correlations were reported between root dry matter and P content in roots (0.90) and between leaf dry matter and P utilization efficiency above the soil level (0.86). These data and high genotypic determination coefficient suggest that selection of best materials may be done with material with highest leaf dry matter weight.

Germinação de sementes e crescimento inicial de maracujazeiros irrigados com água salina em diferentes volumes de substrato

No período de novembro de 2000 e fevereiro de 2001, estudaram-se os efeitos da salinidade da água de irrigação aos níveis de 0,5; 1,0; 2,0; 3,0; 4,5 e 6,0 dS m-1 e dos volumes de substrato: 0,34 e 1,41 L sobre a germinação de sementes e algumas variáveis de crescimento inicial em plantas de maracujá-amarelo e roxo (Passiflora edulis f. flavicarpa Deg). Os resultados mostraram que, independentemente da cultivar, apesar de a água salina inibir a germinação e o desenvolvimento das plantas, os efeitos foram mais danosos nos tratamentos com menor volume do substrato. Ambos os genótipos sofreram mais a ação da salinidade durante o crescimento inicial avaliado pela altura, diâmetro do caule, área foliar, crescimento da raiz principal e biomassa das raízes e parte aérea, que por ocasião da germinação das sementes. As mudas irrigadas com águas de condutividade elétrica superior a 1,0 dS m-1 não apresentaram qualidade para plantio.

Vegetative production of kenaf and canola under irrigation in central California

Kenaf ( Hibiscus cannabinus L.) and canola ( Brassica napus L.) are potential alternative crops for forage production and phytoremediation adaptable to irrigated agriculture in central California. However, little information is available on the water requirements for growing these crops under irrigated conditions, particularly with regard to increasing their vegetative growth. A 3-year field study was undertaken to evaluate kenaf (cultivars: 7-N, Everglades-41, Tainung-2 and breeding lines: C-531, C-533) and one variety of canola (Westar) for potential cultivation. Kenaf was grown as a spring crop and canola was grown as a fall crop. Plants were irrigated at five different levels, ranging from 368 to 1413 mm for kenaf and from 62 to 359 mm for canola per growing season. For kenaf, shoot and root dry matter (DM) production increased as irrigation was increased incrementally from 25 to 125% crop evapotranspiration ( Et c); water application at 150% Et c had no increased benefit. Bark:core ratio of the various kenaf cultivars, however, was unaffected by the level of irrigation. For canola, shoot DM and leaf:stem ratio increased with irrigation up to 125% Et c, whereas root DM did not differ significantly among irrigation treatments. Kenaf produced at least twice as much biomass as canola and both crops produced maximum vegetative yields at 100–125% Et c in central California.

Efeito do alumínio sobre o crescimento de duas espécies florestais

Para estudar o efeito do Al no crescimento inicial de duas espécies florestais, foi instalado um experimento em novembro de 1998, em solução nutritiva, em casa de vegetação do Departamento de Ciência do Solo da Universidade Federal de Lavras. Após duas semanas em solução nutritiva diluída a 1/3 e sem Al, duas plantas de Moringa (Moringa oleifera) e duas de Angico (Anandenantha peregrina) foram transplantadas para vasos de 1,5 L e crescidas em solução nutritiva. Os teores de Al utilizados foram de 0,0; 2,5; 5,0; 7,5; e 10,0 mg L-1, com pH 4,0 ± 0,2, ajustado diariamente durante 70 dias. Após este período, foi determinada a altura das plantas, as quais, posteriormente, foram divididas em parte aérea e raiz, para determinação da matéria seca e dos teores de N e P. Os teores crescentes de Al reduziram progressivamente a altura das plantas e a produção de matéria seca das raízes nas duas espécies e da parte aérea no Angico. O teor de nitrogênio na Moringa diminuiu com o incremento nos teores de Al. O teor de fósforo na parte aérea da Moringa e do Angico diminui a partir de 5 mg L-1 de Al na solução nutritiva.