Root Dry Weight Ratio Research Articles

Effect of different arbuscular mycorrhizal fungi on growth and physiology of maize at ambient and low temperature regimes.

The effect of four different arbuscular mycorrhizal fungi (AMF) on the growth and lipid peroxidation, soluble sugar, proline contents, and antioxidant enzymes activities of Zea mays L. was studied in pot culture subjected to two temperature regimes. Maize plants were grown in pots filled with a mixture of sandy and black soil for 5 weeks, and then half of the plants were exposed to low temperature for 1 week while the rest of the plants were grown under ambient temperature and severed as control. Different AMF resulted in different root colonization and low temperature significantly decreased AM colonization. Low temperature remarkably decreased plant height and total dry weight but increased root dry weight and root-shoot ratio. The AM plants had higher proline content compared with the non-AM plants. The maize plants inoculated with Glomus etunicatum and G. intraradices had higher malondialdehyde and soluble sugar contents under low temperature condition. The activities of catalase (CAT) and peroxidase of AM inoculated maize were higher than those of non-AM ones. Low temperature noticeably decreased the activities of CAT. The results suggest that low temperature adversely affects maize physiology and AM symbiosis can improve maize seedlings tolerance to low temperature stress.

ROOT GROWTH OF UPLAND RICE GENOTYPES AS INFLUENCED BY NITROGEN FERTILIZATION

The plant root system is an important organ which supplies water and nutrients to growing plants. Information is limited on influence of nitrogen fertilization on upland rice root growth. A greenhouse experiment was conducted to evaluate influence of nitrogen (N) fertilization on growth of root system of 20 upland rice genotypes. The N rate used was 0 mg kg−1(low) and 300 mg kg−1(high) of soil. Nitrogen X genotype interactions for root length and root dry weight were highly significant (P < 0.01), indicating that differences among genotypes were not consistent at two N rates. Overall, greater root length, root dry weight and tops-roots ration were obtained at an N fertilization rate of 300 mg kg−1compared with the 0 mg N kg−1soil. However, genotypes differ significantly in root length, root dry weight and top-root ratio. Nitrogen fertilization produced fine roots and more root hairs compared with absence of N fertilizer treatment. Based on root dry weight efficiency index (RDWEI) for N use efficiency, 70% genotypes were classified as efficient, 15% were classified as moderately efficient and 15% were classified as inefficient. Root dry weight efficiency index trait can be incorporated in upland rice for improving water and nutrient efficiency in favor of higher yields.

Effects of Superabsorbent and Irrigation Regime on Seedling Growth Characteristics of Barley (Hordeum Vulgare L.)

Abstract Greenhouse experiment was carried out to study the effects of superabsorbent and water deficit stress on seedling growth of barley (Hordeum vulgare L.) in Urmia University of Iran. Three amounts of superabsorbent polymer (0 (S1), 2 (S2) and 4 g (S3) were mixed with 500 g soil before sowing, and four levels of irrigation regimes (irrigation at 20 (I1), 40 (I2), 60 (I3) and 80% (I3) field capacity) were set as treatments. The root length, root volume, root and shoot dry weight, plant height, leaf length, leaf width, SPAD and root-shoot ratio were affected by treatments. Means comparisons indicated that the highest root length (19 cm) observed in the I4 irrigation regime and the lowest of it (16.18 cm) obtained in I1 condition. Barley plants that received 4 g and no superabsorbent had the utmost (1.13 cm) and lowest (0.54 cm) root volume, respectively. Whereas plant situated in I4 and I1 irrigation regimes produced greatest and smallest amount amount of shoot dry weight and SPAD. The maximum (12.83 cm) and minimum (8.33 cm) leaf length was obtained from S3I3 and S1I1 condition, respectively. Generally, the results showed the most of measured barley seedling traits in irrigation at 40 % field capacity (I2) were the equal with I3 and I4 irrigation regimes treatments, which indicated the resistance of barley seedling to the water deficit stress. Also, we found that the improving of root dry weight and root volume of barley seedling along with increasing in the superabsorbent application.

Implications of Azospirillum brasilense inoculation and nutrient addition on maize in soils of the Brazilian Cerrado under greenhouse and field conditions

The combination of nitrogen and Azospirillum can ensure greater nutrient absorption and crop yield in agricultural areas using high technology. Thus, the objective was to evaluate maize response to Azopirillum brasilense (AZ) inoculation and nutrient (macronutrients and micronutrients) application under greenhouse and field conditions in clay and sandy soils of the Brazilian Cerrado. In the greenhouse assays, the following parameters were measured: shoot dry weight (SDW), root dry weight (RDW), and root volume (RV). In the field experiments, the maize yield was determined after drying the grains at 60°C for 48h. In clay soil, there was a significant increase in the SDW, RDW and RV in the treatment with AZ concentrated (1011cellsml−1 of inoculum) when compared with the control treatment and the treatment with AZ diluted (106cellsml−1 of inoculum). In this soil, adding micronutrients did not affect the maize response under greenhouse conditions. In sandy soil, there was no difference between the AZ treatment and the control, except for treatments where nutrients and AZ were both added leading to a significant increase in the maize response. In both soils, the RV:RDW ratio was higher in the treatment with AZ concentrated compared to that in the treatment with AZ diluted, but the yield response depended on the addition of nutrients. Inoculation with A. brasilense gave comparable yield to the nitrogen treatment. The grain production was increased by 29% in the treatment with A. brasilense and nitrogen compared to nitrogen fertilization alone. In this study, the yield response was affected significantly when maize was inoculated with A. brasilense, but this response was dependent on the soil type under greenhouse conditions.

Provenance variation in survival, growth and dry matter partitioning of Parkia biglobosa (Jacq.) R.Br. ex G.Don seedlings in response to water stress

The effects of drought stress on growth and dry matter partitioning of seven provenances of Parkia biglobosa were assessed in a nursery experiment. Three different water regimes were applied: soil high, medium and low water content (HWC, MWC and LWC) corresponding respectively to 100, 75 and 50 % of field capacity. A split-plot experimental design was applied with the provenance as main plot and the water regime as sub-plot, replicated three times. Each provenance was represented by 30 seedlings in each replication, corresponding to three test periods with ten seedlings each (6, 12 and 18 months after water stress started). There were significant interactions between provenance and water regime for survival rate and the relative growth rates of diameter and height. After 18 months, the dry matter mean was 20.00 ± 0.65 g for the HWC regime, 11.50 ± 2.90 g for the MWC regime while all plants in the LWC regime died. After 6 months, the accumulated water use efficiency (WUE) showed significant differences between water regimes, but not between provenances. Seedlings from the LWC regime showed higher WUE than those from the MWC regime. However, the HWC regime displayed the highest mean value of WUE. Despite differences between provenances, it was not possible to clearly separate them according to the geographical position or climatic parameters, based on the growth performance or both fresh to dry weight and shoot to root dry weight ratios.

Application of silica to suppress the disease infestation of Phytium ultimum and increase growth of Bermudagrass cv Satiri

An experiment was conducted at glasshouse of Unit Latihan Turf, Taman Pertanian, Universiti Putra Malaysia, to find out the effect of different doses of silica (Si) on growth of Bermuda cv Satiri and to suppress the Pythium ultimum disease infestation. Two sources of silica were used in this study: Turf speed® (T. speed), content 15% of potassium silicate (Kâ‚‚SiO₃) and Tune up®, content 10% Sodium Silicate (SiO2). Percent disease severity, shoot density, total dry weight, root and shoot dry weight and root-shoot ratio were determined. Application of Turf speed 10 ml L-1 produced the highest shoot density (125/25 cm²), shoot dry weight (2.49 g) and total dry weight (4.76 g). Tune up (1.0 ml L-1) and without application of any Si produced the highest disease severity (73.69%) and (69.75%) respectively, while, Tune up (1.0 ml L-1) produced the lowest disease severity (44%). The study proved that application of T. Speed (10 ml L-1) and Tune up 2.0 ml L-1produced good growth, quality and reduced P. ultimum infection of Bermuda cv Satiri. Key words: Bermuda cv Satiri, Pythium ultimum, shoot density, relative value, turf quality.

Maize cob plus husks mimics the grain sink to stimulate nutrient uptake by roots

To differentiate the impacts of grains (reproductive tissues) and cob plus husks (vegetative tissues) on biomass accumulation, nitrogen (N), phosphorus (P), and potassium (K) uptake and their distribution within maize plants, six Chinese maize varieties with different yield potentials released in last 60 years were employed in a two-year field experiment. Ears were either covered or removed at silking, the dry weight (DW) and NPK contents at silking and maturity in major sink organs of plants were closely observed. In comparison with control plants, covering ears reduced, and removing ears further decreased total DW and NP gains of whole plants, regardless of the larger root size and reduced shoot:root DW ratio. Since the total DW and NP gains of the new maize varieties after silking were more than that of the old varieties, the decrease of the total DW and NP gains caused by pollination-prevention and removing ears were also more in the new varieties. The uptake and distribution patterns of NP and K in maize plants were different. Developing grains and cob plus husks differentially reduced net post-silking K loss. The results suggested that the amount of nutrient uptake was not decided by the root size itself. Developing maize grains enhanced nutrient uptake rate of roots. The cob plus husks could partially substitute for grains as a strong nutrient sink to stimulate NP uptake by roots and reduce K loss from plants.

Influence of Planting Methods on Root System Morphological and Physiologi-cal Characteristics of Super Rice under High-yielding Cultivation Condition

A field experiment was conducted to compare the root system morphological and physiological characteristics of two super rice cultivars(Huaidao9 and Xudao3) using three planting methods,i.e.,precision artificial transplanting with dry nursery middle and strong seedlings(AT),mechanical transplanting with small seedlings(MT) and direct seeding(DS).Results were as follows.(1) Yields of super rice under different planting methods were very significantly different.Compared with AT,yields of MT and DS reduced by 5.05% and 13.68%,respectively.(2) The population root number was DSMTAT,while the difference was decreasing with the growing process.Total population root length was shown to be DSMTAT at jointing and MTATDS at heading and maturity.Root number per stem showed no significant difference among different planting methods,and total root length per stem was ATMTDS with generally significant difference.Length of single root was of no significant difference be-tween AT and MT,though both were significantly higher than DS.As for root diameter,the result was ATMTDS and the dif-ference among different planting methods was significant.(3) Population root dry weight showed no significant difference be-tween MT and DS at jointing,that both had the extremely significantly higher value than AT.There was no significant difference among different planting methods at heading,but when at maturity it was ATMTDS and the difference was very significant.As for decreasing rate of population root dry weight after heading,it was DSMTAT with significant difference.Root dry weight per stem was ATMTDS through jointing,heading and maturity,and the difference among different planting methods was mostly very significant.Decreasing rate of root dry weight per stem after heading displayed no significant difference between DS and MT,but both of them had the significantly higher value than AT.Shoot dry weight reduced in order for AT,MT,and DS,but root-shoot ratio increased in the same order.(4) Compared with AT,roots of MT and DS were mainly distributed within the soil layer of 0-10 cm underground,especially for DS,the root proportion in 0-5 cm soil layer could sum up to 65%.Ratio of root dry weight in 0-5 cm soil layer to total root weight increased in order for AT,MT,and DS,while the ratios in the soil layers of 5-10 cm,10-15 cm and 15 cm reduced in that order.(5) Population root absorption area showed no significant difference among dif-ferent planting methods at jointing,performed as ATMTDS at heading with very significant difference,and,at maturity,showed no significant difference between MT and AT,both of which had the very significantly higher value than DS.Root ab-sorption area per stem was of no significant difference between AT and MT at jointing and maturity while both had the very sig-nificantly higher value than DS,and was ATMTDS at heading with very significant difference.(6) Population root bleeding intensity after heading increased in order for AT,MT,and DS,but root bleeding intensity per stem reduced in the same order.The results suggested that planting methods have significant influence on root morphological and physiological characteristics of super rice.The different single root length and diameter and the difference in root distribution pattern in soil layer are two most signifi-cant characteristics of rice roots under different planting methods.Compared with AT and MT,the DS method develops roots of shallower distribution,smaller single root length and diameter and higher population root number,though with shorter total root length per stem,lower root dry weight,and less absorption area and bleeding intensity after heading.Compared with AT,root diameter of MT was smaller,distribution shallower,after heading root dry weight of plant population and of single stem both lower and declining faster,and total root length and bleeding intensity per stem inferior.

Identification of quantitative trait loci associated with low boron stress that regulate root and shoot growth in Brassica napus seedlings

Brassica napus (Brassicaceae) is among the most important oil crops and a promising biofuel. In the tropics and subtropics, boron (B) deficiency is a major factor limiting Brassica yields. The effect of B on the regulation of root and shoot growth in a doubled haploid (DH) population was evaluated in experiments that utilized hydroponic culture. Strong genetic variability for traits of interest at normal and low B concentrations was demonstrated. Quantitative trait loci (QTL) were analyzed for seven plant growth parameters: increment of primary root length (IPRL), shoot dry weight (SDW), root dry weight (RDW), ratio of RDW to SDW (R/S), shoot B accumulation (SBA), root B accumulation (RBA), and ratio of RBA to SBA [(R/S)BA] in the population. Twenty-seven QTL were detected at normal B levels: four for IPRL, seven for SDW, three for RDW, two for R/S, six for SBA, two for RBA, and three for (R/S)BA. At low B, 18 QTL were detected: four for IPRL, three for SDW, two for RDW, two for R/S, five for SBA, one for RBA, and one for (R/S)BA. Three QTL for adaptability were detected: one A_IPRL and two A_SDW. No putative QTL was detected at both low and normal B. B-related genes were mapped in silico and their locations compared with the QTL identified. The present analyses show the profound and varied effects of B on B. napus and studies on QTL related to B efficiency will help to locate candidate genes and elucidate possible functions of B-efficiency-related QTL.

Mapping QTLs for Seminal Root Architecture and Coleoptile Length in Wheat

Root system is important for belowground nutrients acquisition, and is also an important part to respond to drought stress. The purpose of this study was to dissect the genetic basis of seminal root architecture and coleoptile length of wheat by mapping quantitative trait loci (QTLs) of target traits. A doubled haploid (DH) population with 150 lines derived from a cross between two common Chinese wheat varieties Hanxuan 10 and Lumai 14 was used as the plant materials. Gel-chamber was em- ployed to evaluate seminal root architecture traits, including maximum root length (MRL), root number (RN), total root length (TRL), root diameter (RD), root angle (RA), ratio of root dry weight to shoot dry weight (RDW/SDW), and coleoptile length (CL) of seedlings. QTLs for these traits were detected using mixed-model-based composite interval mapping method. A total of 12 additive-effect QTLs and 7 pairs of additive × additive QTLs associated with the target traits were mapped on chromosomes 1A, 1B, 2B, 2D, 3B, 4A, 4D, 5A, 5B, 6A, 7A, and 7B. The phenotypic variation explained by individual additive-effect QTL varied from 5.64% to 12.37%. The additive effects ranged from 0.02 to 8.45. The phenotypic variation explained by each pair of epistatic QTLs varied from 8.70% to 15.90%. The epistatic effects ranged from 0.20 to 7.45. Two QTL clusters for seedling root traits were detected on chromosomes 3B and 7A. These results would be helpful to maker-assisted selection of seminal root architecture and coleoptile.

Effect of a phosphonium salt grafted on polymers on cucumber germination and initial growth

The aims of this study were the synthesis, characterization and the testing of vinyldiphenylphosphonium salt phytotoxicity. Phytotoxicity of the synthesised salt was tested on Cucumis sativus L. seed germination and early seedling growth, at five different concentrations, using a standardized toxicity test. Endpoints included the determination of some seedling parameters: root and shoot length, root and shoot biomass, root and shoot dry weight ratio and final germination percentage. The vinyldiphenylphosphonium salt showed moderate to strong root length and root biomass inhibition, which increases progressively with the increasd of the concentration level.

Influência da luz e substrato na germinação e desenvolvimento inicial de duas espécies de Calliandra Benth: (Mimosoideae - Leguminosae) endêmicas da Chapada Diamantina, Bahia

O gênero Calliandra Benth. (Leguminosae) possui 134 espécies exclusivamente neotropicais, das quais 42 ocorrem na Chapada Diamantina, sendo 32 endêmicas da área. O objetivo deste trabalho foi avaliar o efeito da luz e substrato na germinação e desenvolvimento inicial de C. viscidula e C. hygrophila. As sementes foram submetidas a três tratamentos em laboratório: luz, escuro e luz/escuro (12 h/12 h). Em viveiro foram utilizados três substratos: (I) areia; (II) terra vegetal + areia; (III) vermiculita + terra vegetal + areia, mantidos a 100%; e 70% de luminosidade. As avaliações da germinação foram diárias durante 21 dias, utilizando-se os parâmetros: germinabilidade, índice de velocidade de germinação (índice de velocidade de emergência para viveiro), tempo médio de germinação e frequência relativa. Os parâmetros analisados no desenvolvimento inicial foram: comprimentos da parte aérea e raiz, número de folhas, massa seca, relação parte aérea/sistema radicular e razão do peso da folha. C. viscidula e C. hygrophila foram classificadas como fotoblásticas neutras e apresentaram melhor desenvolvimento a 70% de luminosidade nos substratos III e I e II , respectivamente.

Prolonged root hypoxia effects on enzymes involved in nitrogen assimilation pathway in tomato plants

In order to investigate the effects of root hypoxia (1-2 % oxygen) on the nitrogen (N) metabolism of tomato plants (Solanum lycopersicum L. cv. Micro-Tom), a range of N compounds and N-assimilating enzymes were performed on roots and leaves of plants submitted to root hypoxia at the second leaf stage for three weeks. Obtained results showed that root hypoxia led to a significant decrease in dry weight (DW) production and nitrate content in roots and leaves. Conversely, shoot to root DW ratio and nitrite content were significantly increased. Contrary to that in leaves, glutamine synthetase activity was significantly enhanced in roots. The activities of nitrate and nitrite reductase were enhanced in roots as well as leaves. The higher increase in the NH4+ content and in the protease activities in roots and leaves of hypoxically treated plants coincide with a greater decrease in soluble protein contents. Taken together, these results suggest that root hypoxia leaded to higher protein degradation. The hypoxia-induced increase in the aminating glutamate dehydrogenase activity may be considered as an alternative N assimilation pathway involved in detoxifying the NH4+, accumulated under hypoxic conditions. With respect to hypoxic stress, the distinct sensitivity of the enzymes involved in N assimilation is discussed.

Study of influence of temperature regimes on germination characteristics and seed reserves mobilization in wheat.

In a laboratory, experiment germination characteristics and seed reserves mobilization of wheat cultivars were evaluated at three temperature regimes (16, 26 and 36°C). Four heat tolerant cultivars (Gourab, Sourav, Kanchan and Shatabdi) and two heat sensitive cultivars (Sonora and Kalyansona) were used as study materials. Germination characteristics expressed as rate of germination, coefficient of germination and germination vigor index, increased with an increase in temperature. The shoot dry weight and shoot to root dry weight ratio, increased with increasing temperature. But in root dry weight, the highest values were found to be 26°C compared to 16 and 36°C temperature. The dry matter distributed in shoot and the respiratory loss, increased with increasing temperature in all the cultivars. But these increments were greater at 16 - 26°C than those at 26 - 36°C. Therefore, temperature had a profound effect on seed metabolic efficiency (SME). At moderate temperature (26°C), all the cultivars showed the highest SME than the lowest (16°C) and highest temperatures (36°C). Heat tolerant cultivars attained higher SME (2.55 - 2.88 g/g) than those of heat sensitive cultivars (Sonora and Kalyansona) (2.00 - 2.1 g/g). Key words: Wheat, temperature, germination, seed metabolic efficiency.

STUDIES ON NURSERY MANAGEMENT IN PAPAYA (CARICA PAPAYA L.) VAR. CO2

Considering the need for optimizing the number of seedling per bag, an attempt was made with different organic potting mixtures and number of seedlings per polythene bag on growth and development of papaya var. CO2 in the nursery and their effect on first flowering height and first bearing height in the main field. The study revealed the superiority of single seedling grown with potting mixture treated with vermicompost by registering higher seedling height (28.50 cm), seedling diameter (0.639 cm), petiole length (6.410 cm), petiole diameter (0.186 cm), number of leaves (11.65), short dry weight (1.254 g), root length (29.715 cm) root dry weight (0.392 g) and root shoot ratio (0.340). In main field condition, three seedlings per polybag grown with potting mixture and vermicompost was found to have early flowering development (86.69 days) and first bearing height (96.695 cm) with minimum plant height (90.930 cm).

Predicting field performance of five irrigated tree species using seedling quality assessment in Burkina Faso, West Africa

Five exotic tree species (Acacia angustissima (Mil.) Kuntze, A. mangium Wild, Gliricidia sepium (Jacq.) Alp., Leucaena hybrid (L×L), and Leucaena leucocephala (Lam.) de Wit) were investigated to determine whether parameters of nursery seedling stock quality could be used to predict their field performance in a plantation irrigated with treated waste-water to produce fodder and wood. Plants were grown in the nursery in two contrasting rooting substrates (ordinary nursery soil and sand), predicted to have different effects on resource allocation. Three categories of morphological indicators were measured, i.e., plant dimensions (height, diameter, root length), plant weights (shoot, root and whole plant weights) and indices (sturdiness quotient ‘SQ’, shoot:root dry weight ratio ‘SRR’ and Dickson’s quality index ‘DQI’). In the nursery, all species performed better in the ordinary nursery soil for all growth parameters except root length. Thus ordinary nursery substrate appeared superior to sand in terms of plant quality. However, a follow up at plantation phase revealed that only some morphological attributes or ratios were suitable to predict field performance for the five tested species in irrigated plantation. In addition, the effect of the substrate observed at the nursery stage had disappeared 12 months after out planting due to the availability of water and nutrients provided by the treated waste water used for the irrigation. The results showed that root collar diameter and DQI appeared to be the most appropriate indicators to predict the outplanting performance of the five tested species in a short-rotation irrigated plantation in semi-arid Burkina Faso. The former measure is simpler and non-destructive.

Coinoculation of Bacillus thuringeinsis-KR1 with Rhizobium leguminosarum enhances plant growth and nodulation of pea (Pisum sativum L.) and lentil (Lens culinaris L.)

Nodulation and the subsequent nitrogen fixation are important factors that determine the productivity of legumes. The beneficial effects of nodulation can be enhanced when rhizobial inoculation is combined with plant-growth-promoting bacteria (PGPB). The PGPB strain Bacillusthuringiensis-KR1, originally isolated from the nodules of Kudzu vine (Puerariathunbergiana), was found to promote plant growth of field pea (Pisumsativum L.) and lentil (Lensculinaris L.) under Jensen’s tube, growth pouch and non-sterile soil, respectively, when co-inoculated with Rhizobiumleguminosarum-PR1. Coinoculation with B. thuringiensis-KR1 (at a cell density of 106 c.f.u. ml−1) provided the highest and most consistent increase in nodule number, shoot weight, root weight, and total biomass, over rhizobial inoculation alone. The enhancement in nodulation due to coinoculation was 84.6 and 73.3% in pea and lentil respectively compared to R. leguminosarum-PR1 treatment alone. The shoot dry-weight gains on coinoculation with variable cell populations of B. thuringiensis-KR1 varied from 1.04 to 1.15 times and 1.03 to 1.06 times in pea and lentil respectively, while root dry weight ratios of coinoculated treatments varied from 0.98 to 1.14 times and 1.08 to 1.33 times in pea and lentil respectively, those of R. leguminosarum-PR1 inoculated treatment at 42 days of plant growth. While cell densities higher than 106 c.f.u. ml−1 had an inhibitory effect on nodulation and plant growth, lower inoculum levels resulted in decreased cell recovery and plant growth performance. The results of this study indicate the potential of harnessing endophytic bacteria of wild legumes for improving the nodulation and growth of cultivated legumes.

Parâmetros morfológicos de mudas de Sesbania virgata (Caz.) Pers e de Anadenanthera peregrina (L.) cultivadas em substrato fertilizado com composto de lixo urbano

Objetivou-se avaliar o efeito do composto de lixo urbano nos parâmetros morfológicos de mudas de sesbânia e de angico. Os substratos de cultivo tiveram as seguintes proporções de composto e de amostras de subsolo de Neossolo Quartzarênico ou de Latossolo Vermelho-Amarelo (%): 0:100; 20:80; 40:60; 60:40 e 80:20, sem a utilização de fertilização mineral. As sementes de sesbânia foram inoculadas com a estirpe recomendada BR 5401. Os parâmetros morfológicos das mudas de sesbânia e angico, suas relações e índice de qualidade de Dickson (IQD) foram determinados aos 56 e 120 dias após a semeadura, respectivamente para cada espécie. Os efeitos dos substratos nos parâmetros morfológicos das mudas de sesbânia e angico variaram de acordo com as proporções do substrato. Para o angico, a adição do composto proporcionou aumento na altura da parte aérea, razão entre massa seca de parte aérea por massa seca de raiz e IQD. Para sesbânia, a adição do composto de lixo ao substrato proporcionou aumento na altura da parte aérea, diâmetro do coleto, massa seca de raiz, da parte aérea e total, razão entre massa seca da parte aérea por massa seca de raiz, IQD e número de nódulos. A obtenção de máxima produção de matéria seca total, diâmetro do coleto e IQD foi de 57:43, sendo, portanto, esta a proporção composta de lixo:solo recomendada para a produção de mudas de sesbânia.

Contribution of cotyledons to seedling dry weight and development in Medicago falcata L.

Three experiments are reported, two of which involved cotyledon excision, to elucidate seedling developmental strategy of a North China rangeland legume, Medicago falcata. Early loss of cotyledons was fatal, with data indicating a possible hormonal‐type signal from cotyledons to initiate first leaf expansion. Cotyledons made a substantive photosynthetic contribution for some 28 days from imbibition, but high seedling relative growth rates were not observed until after first leaf expansion. On removal of both cotyledons at 7 days, seedlings responded with an increase in shoot:root dry weight ratio; on removal of one cotyledon only at this time a transitory shift of allocation from shoot to root was observed until normal ontogeny was restored. Removal of one or both cotyledons at 14 days delayed seedling development but did not change seedling ontogeny. This study was part of a series of experiments to better understand the autecology of M. falcata.

Treating eutrophic water for nutrient reduction using an aquatic macrophyte ( Ipomoea aquatica Forsskal) in a deep flow technique system

Wetlands can be used in a cost-effective manner to treat nutrient-rich water for release to freshwater ecosystems. Eutrophic water was treated with the freshwater macrophyte, Ipomoea aquatica Forsskal (swamp cabbage), in a horizontal-flow, Deep Flow Technique (DFT) system. Plants were also exposed to a Hoagland and Arnon [Hoagland, D.R., Arnon, D., l938. The water culture method for growing plants without soil. Calif. Agr. Expt. Sta. Circ., 347] solution using the same exposure system. After a 48-h exposure to the plant, chemical oxygen demand (COD), biochemical oxygen demand (BOD 5), total suspended solids (TSS) and chlorophyll a (Chla) in the effluent were reduced by 84.5, 88.5, 91.1, and 68.8%, respectively, and the removal of nutrients (total nitrogen and total phosphorus) varied between 41.5 and 75.5%. Vitamin C and NO 3-N concentrations in plants grown in the eutrophic water were significantly different from those grown in a standard nutrient solution. Chlorophyll a, chlorophyll a/ b and shoot to root dry weight ratio were not significantly different between the different waters. The concentrations of cadmium, copper, lead and zinc were lower than the permissible levels set by the FAO and WHO for human consumption. The results of this study indicate that cultivating edible, aquatic macrophytes with nutrient-rich, eutrophic water in a DFT system can be an effective, low-cost phytoremediation technology to treat water with undesirable levels of nitrogen and/or phosphorus.