Stalk Production Research Articles

高分球性アジアティックハイブリッドユリ ‘きたきらり’ における鱗片繁殖後の球根サイズが抽苔， 分球および球根重に及ぼす影響

高分球性アジアティックハイブリッドユリ ‘きたきらり’ における鱗片繁殖後の球根サイズが抽苔， 分球および球根重に及ぼす影響

Contrasting effects of low‐level phosphorus and nitrogen enrichment on growth of the mat‐forming alga Didymosphenia geminata in an oligotrophic river

Summary The stalked diatom Didymosphenia geminata forms proliferations of stalk‐dominated mats in rivers. Over its range in New Zealand, mats rarely occur where average dissolved reactive phosphorus (DRP) concentrations exceed ~2 mg m−3, but do occur in rivers with dissolved inorganic nitrogen (DIN) concentrations up to ~250 mg m−3. Previous studies indicated that low DRP concentrations limit D. geminata cell division and stimulate stalk production and mat development, even at very low ambient DIN concentrations (~10 mg m−3). We ran two nutrient‐enrichment experiments in instream channels in an oligotrophic river with a persistent D. geminata proliferation to (i) test the hypothesis that elevated DRP concentrations reduce or prevent mat development by reducing stalk production; and (ii) investigate the effect of DIN enrichment on D. geminata growth and mat development. In Experiment 1, treatments comprised low‐level enrichment with DRP (to 1.6 mg m−3, from superphosphate fertiliser), DIN (to 13.5 mg m−3, from ammonium sulphate), and both DRP and DIN. Compared to unenriched controls, DIN and DRP enrichment enhanced D. geminata cell densities, biomass, cell division (frequency of dividing cells), stalk biovolume and percentage cover of mats, indicating both N‐ and P limitation for all growth metrics. In the DRP‐enriched treatments, biomass accrual may have been stimulated rather than reduced as predicted because DRP concentrations did not exceed the putative 2 mg m−3 threshold. In Experiment 2, we expanded the range of DRP enrichment using additions of orthophosphate as well as superphosphate, and added DIN to all treatments. Higher DRP concentrations (up to 4 mg m−3) initially enhanced D. geminata growth. By the end of the experiment, D. geminata‐dominated biomass in the orthophosphate treatments was lower than in the superphosphate or DIN‐only treatments. Outflows from the experimental channels caused slight nutrient enrichment in the river downstream. During Experiment 1, this DRP and DIN enrichment had no detectable effect on D. geminata standing crop on the riverbed. During Experiment 2, D. geminata standing crop downstream of the experiment declined relative to the unenriched area upstream. The specific mechanism linking P enrichment to D. geminata biomass decline is unclear. In the experimental channels there was evidence for a predominance of cell division over stalk production in orthophosphate treatments, as hypothesised. In the river, we observed higher rates of sloughing in the river downstream of the experiment than upstream. There was no evidence that competition from other algal taxa reduced D. geminata standing crop. The results supported the hypothesis that DRP enrichment at concentrations over ~2 mg m−3 leads to reduced D. geminata biomass and % cover in this river. However, biomass reduction occurred only when DRP was added as orthophosphate, not as superphosphate. N limitation of D. geminata growth in river water with ambient mean DIN concentrations below ~6 mg m−3 suggests that D. geminata proliferations may be stimulated by increases in DIN concentration in rivers where both DIN and DRP are naturally low. The threshold for N limitation was ~10 mg m−3.

Production of phosphatase and extracellular stalks as adaptations to phosphorus limitation in Didymosphenia geminata (Bacillariophyceae)

Didymosphenia geminata is a benthic bloom-forming diatom that is invasive in many temperate, oligotrophic freshwater ecosystems. D. geminata blooms are unusual, resulting from prolific basal stalk production stimulated by phosphorus limitation. The adaptive value of stalk production and bloom development is disputed. We examined blooms in relation to stalk biomass, biovolume and phosphatase activity. An austral summer survey of 15 sites within the Waitaki River of New Zealand compared reference communities (no detectable D. geminata), with those impacted by high and low D. geminata biomass. Sites were compared for differences in phosphatase location and activity using chromogenic substrates, community composition using morphological identifications, and overlying water and pore-water chemistry. Experimental microcosms subjected live proliferations to varied phosphate concentrations, and phosphatase rates and location were examined. Survey results identified phosphatase activity increased with D. geminata biomass, with lowest rates in reference communities. Pools of labile nutrients were detected in D. geminata mats, and in vitro hydrolysis rates were rapid in replete phosphoester conditions (~0.2 mmol l−1 h−1 cm−2 at 16°C), with activity concentrated on stalks. Our results suggest D. geminata bloom development is an adaptation to maximise supply of phosphate under chronic phosphorus limitation.

The effect of timing of growing season drought on flowering of a dominant C4 grass

Timing of precipitation is equally important as amount for determining ecosystem function, especially aboveground net primary productivity (ANPP), in a number of ecosystems. In tallgrass prairie of the Central Plains of North America, grass flowering stalks of dominant C4 grasses, such as Andropogon gerardii, can account for more than 70% of ANPP, or almost none of it, as the number of flowering stalks produced is highly variable. Although growing season precipitation amount is important for driving variation in flowering stalk production, it remains unknown whether there are critical periods within the growing season in which sufficient rainfall must occur to allow for flowering. The effect of timing of rainfall deficit (drought) on flowering of A. gerardii, was tested by excluding rainfall during three periods within the growing season (starting in mid-April, mid-May and mid-June). Mid-summer drought (starting in mid-June) strongly reduced the flowering rate (e.g., density and biomass) of A. gerardii (e.g., as high as 94% compared to the control), suggesting flowering is highly sensitive to precipitation at this time. This effect appeared to be related to plant water status at the time of flowering stalk initiation, rather than an indirect consequence of reduced C assimilation. Our results suggest that increased frequency of growing season drought forecast with climate change could reduce sexual reproduction in this dominant grass species, particularly if it coincides with timing of flowering stalk initiation, with important implications for ecosystem functioning.

エゾリンドウにおける塊茎の発達様式と株齢による花茎生産性の変動

エゾリンドウの4年生株における切り花収量の減少要因を明らかにするため，2年生株から4年生株において，塊茎の発達過程と花茎の発生について調査した．2年生株から3年生株にかけて主塊茎の生育は旺盛になり，副塊茎の多くがこの時期に形成された．3年生株から4年生株にかけては，主塊茎の木化が進んで生育が緩慢になる一方で，副塊茎の発達が旺盛になった．株齢による花茎の発生は主塊茎と副塊茎で異なる傾向を示した．3年生株では，主塊茎からの花茎の発生が旺盛であった．これに対して，4年生株では，旺盛に発達する副塊茎からの花茎の発生が盛んになったものの，主塊茎からの花茎の発生が減少することにより，株全体の花茎発生が減少した．主塊茎の頂芽は栄養芽として存続し，側生器官である花茎と副塊茎を分化し続けた．従って，4年生株における主塊茎の発達の停滞は，無限成長性を維持したまま起こると考えられた．

Potassium nutrition in sugar cane ratoons cultured in red latosol with a conservationist system

ABSTRACTThe aim of this study was to evaluate the effect of potassium addition to the soil in first and second ratoon sugarcane cultures in a conservationist system. The experiment was conducted at the State of Sao Paulo, Brazil, in an Acriferric Red Latosol cultured with a IAC SP 93-3046 cane sugar variety after plant-cane cutting. The experiment involved five potassium treatments and four repetitions in randomized block design. The potassium (K) dosages were 27, 54, 108, and 162 kg K ha−1, and a treatment without potassium. Six months after the start of the experiment, soil samples collected at 0–20 and 20–40 cm in depth were analyzed for K content. Four months after sprouting, plants were evaluated, by tiller numbers, height, diameter, technological analysis of stalks, and nutritional status. In the first ratoon, potassium fertilization increased stalk diameters, increased potassium accumulation in the aerial parts, and increased stalk production. In the second ratoon, there was a water deficiency, and soil application of potassium did not influence plant growth, nutritional status, or production parameters. Application of potassium in cane sugar ratoons did not contribute to stalk technological quality.

Action of growing degree days on the morphogenesis and physiological responses of calla lily

The calla lily (Zantedeschia aethiopica) is an ornamental plant with growing acceptance in the market place that shows thermal constraints during planting. This study aimed to analyse its biological cycle in growing degree days (GDD) to determine the best time for planting and production of flower stalks. Rhizomes were planted in pots during all four seasons, and the pots were kept in a greenhouse. Growth analysis and gas exchange measurements were performed every 30 days. Rhizomes planted in the fall and summer showed greater shoot growth, a larger root system and increased production of flower stalks, and they remained in the vegetative phase longer before the onset of flowering, attaining a lower GDD value. Rhizomes planted in winter and spring matured early, which resulted in a higher GDD value and a decrease or lack of flower stalk production during this period. Calla lily rhizomes planted in the fall and summer showed higher water-use efficiency, light-use efficiency and net photosynthesis. It is possible to characterise the stages of development according to gas exchange. The calla lily must be cultivated with an irradiance of 250–400 µmol m−2 s−1 in a temperature range of 25–28 °C during the initial growth phase (up to 1,000 GDD). Thereafter, the temperature range should be reduced to between 13 and 15 °C until 3,500 GDD are reached, which was found to enable increased flower stalk production.

The Origin of Invasive Microorganisms Matters for Science, Policy, and Management: The Case of Didymosphenia geminata.

The value of distinguishing native from nonnative invasive species has recently been questioned. However, this dichotomy is important for understanding whether a species’ successful dominance is caused by introductions, changing environmental conditions that facilitate an existing population, or both processes. We highlight the importance of knowing the origin of hard-to-detect invasive microorganisms for scientific research, management, and policy using a case study of recent algal blooms of the stalk-producing diatom Didymosphenia geminata. Nuisance blooms have been reported in rivers worldwide and have been hastily attributed to introductions. However, evidence indicates that blooms are probably not caused by introductions but, rather, by environmental conditions that promote excessive stalk production by this historically rare species. Effective responses to invasive microorganisms depend on knowing whether their proliferation is caused by being nonnative or is the result of changing environmental conditions that promote invasive characteristics of native species.

English

The productivity and fresh phytomass index of sugarcane cultivated at different water replacement levels using a subsurface drip system, with or without N, were analyzed. Sugarcane plants underwent five water replacement levels (100, 75, 50, 25 and 0%), with or without N application (100 kg ha-1) in urea. At harvest-time, stalk productivity, water-use efficiency, gross sugar yield, gross alcohol yield, fresh phytomass of tip, dry leaf phytomass, total fresh phytomass and the ratio between the fresh phytomass of tip and stalk productivity were evaluated. A 100% water replacement increased stalk productivity by 40% compared with drought-stricken area management (water replacement 0%) and high efficiency in the exploitation of photoassimilated in stalk production. N-urea application increased by 14% the gross sugar and alcohol yield. Water deficit (water replacement 0%) caused severe decrease (26%) in total phytomass of the sugarcane plant´s aerial section. Key words: Saccharum officinalis, water replacement, irrigation, nitrogen, water deficit.

Impact of Nitrogen and Sulphur Fertilisers on Yield and Quality of Sugarcane Plant Crop

It is expected that an improvement in nitrogen (N) uptake by plants would occur if sulphur (S) availability in the soil solution is non-limiting. In this study, sugarcane (plant crop) responses to N were studied at different levels of S application. The experiment was performed in Piracicaba city (Sao Paulo State, Brazil), from May 2004 to September 2005. Sugarcane plants were grown in 220 L pots filled with sandy soil. A randomised block design was adopted to evaluate four N doses (0, 40, 80 and 120 kg ha−1 of N) and two S doses (0 and 70 kg ha−1 of S) applied at the time of planting. Responses were observed for sugarcane biomass and stalk production in response to N application 16 months after the planting. The highest N dose (120 kg ha−1) increased aboveground, belowground, and whole plant dry matter and stalk production by 56, 37, 53 and 56 %, respectively, when compared to the treatment without added N. The lowest N doses (0 and 40 kg ha−1) resulted in highest root to shoot ratio. The sugarcane technological parameters (brix, fiber content, juice sucrose) were not affected by N and S application. However, sugar production increased in those doses of N that led to an increased production of stalks: even the lowest application of N (40 kg ha−1) increased sugar production by 14 % in comparison with the zero application. There were no statistically significant effects of the S treatment, so the results of this study do not confirm the hypothesis that S is an interacting factor for sugarcane response to N application. However, this study involved only 1 year of experimentation and needs confirmation.

Produtividade e qualidade da matéria prima de cultivares de cana-de-açúcar submetida à aplicação de herbicidas

Herbicides may cause toxicity to the crop and also negative effects on yield characteristics and industrial quality of sugarcane. This study evaluated the effects ametryn, trifloxysulfuron-sodium, ametryn + trifloxysulfuron-sodium and sulfentrazone herbicides over quality and stalk yield of RB867515, SP801816, SP803280, RB937570 and RB925211 cultivars. The experiment was conducted at the Federal University of Viçosa, Viçosa County, Minas Gerais State. A distinct behavior was observed for the cultivars in the presence of herbicides, both for quality as for the stalk yield. The quality showed greater variability among cultivars than among herbicide treatments that act directly on stalk production and indirectly in sugar production, being ametryn and sulfentrazone herbicides the ones that caused higher negative interference. SP803280 cultivar was the genotype with the lowest susceptibility to herbicides.

Didymosphenia geminata growth rates and bloom formation in relation to ambient dissolved phosphorus concentration

Summary1. The bloom‐forming freshwater stalked diatom Didymosphenia geminata is unusual among algae in that nuisance growths occur almost exclusively in oligotrophic waters. Current hypotheses to explain this phenomenon have assumed supplemental acquisition of phosphorus from novel sources within the stalk/mat matrix.2. We carried out a synoptic survey of river sites in the South Island, New Zealand, to determine whether D. geminata cell division and stalk development (measured as mat coverage or standing crop) were related to ambient phosphorus concentrations in the overlying river water.3. High coverage (>50%) by D. geminata was largely concentrated at sites with mean dissolved reactive phosphorus (DRP) <2 mg m−3 in the overlying water. Didymosphenia geminata was present at only one site with DRP >4 mg m−3, with very low coverage. Cell division rate (measured as the frequency of dividing cells, FDC) was positively correlated with mean DRP suggesting that division rates were controlled by the available phosphorus concentration in ambient river water. At the same time, FDC was negatively correlated with D. geminata standing crop (measured as an index incorporating percentage cover and mat thickness).4. In a single river reach with a stable cross‐channel gradient of total dissolved phosphorus (TDP) caused by inflows from a high‐nutrient tributary, again we observed a negative correlation between percentage cover by D. geminata and concentrations of TDP.5. Finally, we made a series of observations on D. geminata‐dominated communities that had been exposed to water enriched with ‐N and ‐P for 4 weeks, followed by exposure to unenriched water. After 2 weeks of nutrient deprivation, D. geminata cell division rates declined by 60%, mean stalk length increased by 250%, and total carbohydrate quadrupled relative to initial values. The appearance of the community changed from a dark brown mat to a thick pale mat typical of D. geminata blooms.6. All these results indicate that D. geminata cell division rates are actively controlled by concentrations of available phosphorus in the overlying water and that stalk production (represented by mat thickness and extent, stalk length and total carbohydrate) is inversely related to D. geminata cell division rates. They thus support an explanation for D. geminata blooms in oligotrophic rivers tied to enhanced stalk production in nutrient‐poor waters, rather than through acquisition of additional phosphorus through recycling processes within the mat.

ENVIRONMENTAL CONTROL OF STALK LENGTH IN THE BLOOM-FORMING, FRESHWATER BENTHIC DIATOM DIDYMOSPHENIA GEMINATA (BACILLARIOPHYCEAE)(1).

Blooms of the freshwater stalked diatom Didymosphenia geminata (Lyngb.) M. Schmidt in A. Schmidt typically occur in oligotrophic, unshaded streams and rivers. Observations that proliferations comprise primarily stalk material composed of extracellular polymeric substances (EPS) led us to ask whether or not the production of excessive EPS is favored under nutrient-limited, high-light conditions. We conducted experiments in outdoor flumes colonized by D. geminata using water from the oligotrophic, D. geminata-affected Waitaki River, South Island, New Zealand, to determine the relationship between D. geminata stalk length, cell division rates, and light intensity under ambient and nutrient-enriched conditions. Stalk lengths were measured in situ, and cell division rates were estimated as the frequency of dividing cells (FDC). FDC responded positively to increasing light intensity and to nutrient additions (N+P and P). Under ambient conditions, stalk length increased as light level increased except at low ambient light levels and temperature. Nutrient enrichment resulted in decreased stalk length and negative correlations with FDC, with this effect most evident under high light. Our results are consistent with the hypothesis that extensive stalk production in D. geminata occurs when cell division rates are nutrient limited and light levels are high. Thus, photosynthetically driven EPS production in the form of stalks, under nutrient-limited conditions, may explain the development of very high biomass in this species in oligotrophic rivers. The responses of FDC and stalk length under nutrient-replete conditions are also consistent with occurrences of D. geminata as a nondominant component of mixed periphyton communities in high-nutrient streams.

Explaining temporal variation in above-ground productivity in a mesic grassland: the role of climate and flowering

Summary 1. Annual above-ground net primary productivity (ANPP) in mesic grasslands is known to be highly temporally variable. While yearly precipitation or average yearly temperature can explain some of this temporal variability, much of the variation in ANPP remains unexplained. 2. Here we address the heretofore unexplained variation in 25 years of productivity data from a mesic grassland at Konza Prairie (north-eastern Kansas) by examining the effects of precipitation and temperature during periods relevant to the phenology and growth cycle of the dominant C4 grasses and the flowering stalk production of these species. We assessed both the direct effects and indirect effects via flowering of phenologically relevant climate periods on ANPP using structural equation modelling (SEM). 3. We found ANPP to be strongly positively influenced by flowering stalk production of the dominant C4 grasses, precipitation during periods relevant to vegetative growth (15 April–14 July) and flowering stalk elongation (15 July–14 August) of the dominant grasses, and fire. In addition, flowering stalk production was negatively influenced by high temperatures during the flowering stalk elongation period, which therefore resulted in a negative indirect effect on ANPP. We found little evidence for the effects of the previous year’s total annual precipitation or mean annual temperature on ANPP. 4. By including flowering stalk production and separating climate variables into phenologically relevant periods we were able to increase the percentage of observed variance in ANPP explained by six models, relating to different topographic positions and burn regimes, from an average of 22% to 48%, with the best model explaining 61% of variation in ANPP. 5. Synthesis. The link between climatic periods relevant to the phenology and growth of dominant C4 grasses, flowering stalk production of these grasses and ANPP shown here improves our ability to predict productivity in mesic grasslands, an ecologically and economically important ecosystem.

Study on the Hydrolysis of Corn Stalk and Photosynthetic Bacteria Group Fermentation Hydrogen Production

Hydrogen production of photosynthetic bacteria group (PSBG) was studied using corn stalk hydrolyzate as hydrogen production substrate. The effects of sulfuric acid concentration, hydrolysis pH values and hydrolysis temperature on hydrogen production were investigated. The optimum process conditions were as follows: the sulfuric acid concentration was 1%, hydrolysis pH value was 6.0 and the hydrolysis temperature was 110°C , respectively. Three hydrolyzate detoxification methods were compared. The method of calcium hydroxide obtained the optimal detoxification effect and the maximum hydrogen yield was 472 mL H2/ (L-medium).

Potential of some sweet sorghum (Sorghum bicolor L. Moench) varieties for syrup and ethanol production in Egypt

The aim of the present study was to select the suitable sowing date and the proper varieties which perform high yielding ability, juice quality and processing parameters under agro-climatic conditions of El-Giza governorate. Two field trials were carried out at Giza Experimental Station, Agricultural Research Center. Fourteen sweet sorghum varieties were evaluated for their yielding ability, juice quality and processing parameters under two sowing dates i.e. May 5th and 25th. Analysis of variance showed: most yielding traits, juice quality and processing parameters acted better in the early planting date (May 5) than in the late ones (May 25). Great variation in most studied traits has been detected among the fourteen sweet sorghum varieties under investigation. Not all sweet sorghum varieties perform good for stalk, syrup and alcohol production, quality and processing parameters in the first planting date, but some of them were suitable for the second planting date. Varieties viz., Mn3306, Planter, Rex, Rio, SS405 and Tracy were distinguished with high potential ability for producing syrup and ethanol. Therefore, these varieties are recommended for dual purpose.

Crescimento e produtividade agrícola de cana-de-açúcar em diferentes fontes de fósforo

Com o objetivo de avaliar o crescimento e a produtividade agrícola da cana-planta em diferentes fontes de fósforo, conduziu-se um experimento de campo em Coruripe, AL, com 10 tratamentos: 1. Testemunha; 2. NK + micro; 3. Superfosfato simples (SS); 4. Superfosfato triplo (ST); 5. Fosmag; 6. Gafsa; 7. MAP; 8. Fórmula 06-26-24 (460 kg ha-1); 9. Composto e 10. SSP - parcelado. O delineamento estatístico foi em blocos ao acaso com 4 repetições. Avaliaram-se: população de perfilhos, altura de plantas, Índice de Área Foliar (IAF), taxa de crescimento do colmo, taxa de produção de matéria fresca do colmo, taxa de crescimento relativo, rendimento agrícola e as concentrações foliares de P e os níveis disponíveis no solo. As fontes de fósforo não influenciaram o crescimento da cana-planta em função do efeito residual, proveniente de adubações anteriores, mas proporcionaram produtividades médias superiores a 80 t ha-1. O ST proporcionou o melhor rendimento agrícola na cana-planta a qual, por sua vez, apresentou três fases de crescimento: 1ª fase: intenso perfilhamento até 120 DAP; 2ª fase: grande crescimento de 120 a 240 DAP e 3ª fase: maturação dos 240 aos 360 DAP. As maiores taxas de crescimento e produção de matéria fresca do colmo ocorreram logo após a fase de intenso perfilhamento entre 120 e 240 DAP.

Avaliação agronômica da escória de siderurgia na cana-de-açúcar durante cinco ciclos de produção

A escória de siderurgia, como material corretivo de acidez com reação mais lenta que o calcário, poderá beneficiar culturas de ciclo longo como a cana-de-açúcar. Assim, este trabalho teve como objetivo avaliar a resposta da cultura da cana-de-açúcar durante cinco ciclos de produção, decorrente da aplicação da escória de siderurgia. O trabalho foi realizado no município de Ituverava (SP), em Latossolo Vermelho-Amarelo (V=26%). Utilizou-se o delineamento experimental em blocos casualizados, em esquema fatorial 2 x 4, com quatro repetições. Os fatores constituíram-se de dois materiais corretivos (escória de siderurgia e calcário calcítico) e quatro doses: 0; 1,23, 2,52 e 3,8 t ha-1 equivalente a CaCO3. Avaliou-se ao longo de cinco ciclos de cultivo, a produção de colmos (safras 1998/1999 até 2002/2003); nos quatro primeiros ciclos realizou-se a amostragem do solo (camada de 0-20 cm de profundidade) e determinou-se a saturação por bases. A escória de siderurgia e o calcário calcítico foram semelhantes na correção da acidez do solo, ao longo dos ciclos de cultivo da cana-de-açúcar. A maior produção acumulada de colmos está associada à saturação por bases no solo próxima a 60% e 70% para uso do calcário e da escória de siderurgia, respectivamente.

Cultivo de cana-de-açúcar em argissolo tratado com lodo de esgoto: I - Disponibilidade de nitrogênio no solo e componentes de produção

Adotando-se os devidos critérios agronômicos e sanitários, o lodo de esgoto pode ser utilizado como fonte de nutrientes, especialmente N, em solos agrícolas, revertendo em benefícios econômicos e ambientais. Todavia, a estimativa da dose de lodo a ser aplicada é resultante de ensaios de mineralização do N sob condições ótimas de temperatura e umidade que, em parte dos casos, não são encontradas no campo. Nesse contexto, o objetivo deste estudo foi verificar a necessidade de se aplicar N proveniente de uma fonte mineral, prontamente solúvel, ao lodo de esgoto na cultura da cana-de-açúcar em soca. O experimento foi instalado no campo, em um Argissolo Vermelho distrófico cultivado com a variedade RB855536. O ensaio foi realizado durante dois períodos (outubro de 2002 a agosto de 2003 - ano agrícola 2003/04 e outubro de 2003 a outubro de 2004 - ano agrícola 2004/05). Os tratamentos testados foram oito: (a) controle; (b) fertilização mineral (120 kg ha-1 N + 150 kg ha-1 K2O); (c) LE + 0N, incorporado no solo após a aplicação (ISA); (d) LE + 0N, incorporado no solo 60 dias após a aplicação (IS60A); (e) LE + 60 kg ha-1 N (ISA); (f) LE + 60 kg ha-1 N (IS60A); (g) LE + 120 kg ha-1 N (ISA); e (h) LE + 120 kg ha-1 N (IS60A). O lodo de esgoto foi resultante de tratamento biológico e aeróbio, e a dose aplicada foi calculada em função da mineralização do N e suficiente para fornecer 120 kg ha-1 de N. A aplicação de LE resultou em aumento significativo no teor de N orgânico do solo nos dois períodos estudados, porém apenas na camada de 0-20 cm. Com a adição do fertilizante nitrogenado mineral, houve aumento nos teores de N inorgânico (N-NO3- + N-NH4+) na camada de 20-40 cm no ano-agrícola 2003/04 e nas camadas de 0-20 e 20-40 cm em 2004/05. A aplicação de LE resultou num incremento na produção de colmos da ordem de 27 % nos dois anos agrícolas em comparação aos tratamentos que não receberam o resíduo. A quantidade de sacarose da cana-de-açúcar, expressa em termos de açúcar total recuperável (ATR), foi significativamente maior nos tratamentos com lodo de esgoto no ano agrícola 2004/05; neste caso, não houve diferença na adição de N mineral nas doses de 60 e 120 kg ha-1.

Identification of two phenotypes of Arabidopsis thaliana under in vitro salt stress conditions

This study describes two phenotypes of Arabidopsis thaliana (ecotype Columbia) developed in vitro under salt stress (75 mM NaCl). The phenotypes 01 and 02 appeared visibly distinguishable by rosette morphology and competence to produce flowers. Phenotype 01, sensible to salt stress, accumulated high quantities of Na+, showed a slight reduction in dry mass, and high protein and chlorophyll contents. Moreover, its anatomy exhibited some xeromorphic traits. Phenotype 02, clearly salt tolerant, showed a morphology similar to control plants, displaying typical phyllotactic rosette and flowering stalk production. Accumulation of Na+, protein and chlorophyll contents were close to control plants. Reversion experiments on NaCl free MS medium, showed a partially recovered phenotype 01. A threshold salt stress concentration that permits the simultaneous development of two phenotypes, was found.