Plant Water Relations: Absorption, Transport and Control Mechanisms

Although water is abundant on Earth - covering 71% of the total surface - its distribution is not uniform and can easily cause restrictions in availability to vegetal production. At global scale, these restrictions are easily observed in dry climates and can appear in other regions which do not currently experience drought, as provided by the future backdrop of climate change (IPCC, 2007). The influences of water restriction on losses in the production and distribution of vegetation on the terrestrial surface are significantly larger than all other losses combined which are caused by biotic and abiotic factors (Boyer, 1985). This striking effect of water on plants emerges from its physiological importance, being an essential factor for successful plant growth, involving photosynthesis and several other biochemical processes such as the synthesis of energetic composites and new tissue. Therefore, in order to characterise the growth and productive behaviour of plant species it is essential to have an understanding of plant water relations, as well as the consequences of an inadequate water supply. Broadly, the water state of a plant is controlled by relative rates of loss and absorption, moreover it depends on the ability to adjust and keep an adequate water status. This will be considered throughout this chapter

Soybean Architecture Plants: From Solar Radiation Interception to Crop Protection

The soybean plant architecture in relation to better solar radiation interception and production gain is an aspect that requires a better understanding, since soybean is an important crop worldwide. The genetic traits, management and environmental conditions are points that further extend the range of issues on crop productivity. The light quality is measured by the red/far‐red (R/FR) ratio (R ∼ 660 nm, FR ∼ 730 nm). This affects the plant growth and morphological developments in different ways. The plant leaves change their angle during the day to better intercept radiation. This heliotropic movement and some computational models together have been used to enhance some agricultural practices. Soybean plant is dependent on the interaction between genotype and environment. Thus, the enhanced understanding in relation to photosynthetic activity, grain yield by light interception efficiency and culture protection managements in soybean are covered

Grain productive efficiency of soybean plants under lactofen application

Adverse factors cause a decrease in the productive potential of crops. For soybean [(Glycine max (L.) Merrill], the excessive growth is a factor that results in plants with low effective efficiency. Thus, plants with an architecture that favours greater interception of solar radiation and deposition of pesticides tend to be more productive. The objective of this study is to evaluate the different application of lactofen, which is used as a growth inhibitor, improve the productive efficiency of soybeans by increasing the biological activity of the leaves. The study was conducted in the field with soybean cultivars NA 5909 RG and BMX Potência RR. The experiment followed a randomized complete block design with four treatments and five replicates: T1: control; T2: application of 140 g a.i ha-1 of lactofen in phenological stage V3; T3: application of 140 g a.i ha-1 of lactofen in phenological stage V6; and T4: application of 70 g a.i ha-1 of lactofen in phenological stage V3 + 70 g a.i ha-1 of lactofen in phenological stage V6. The interception of photosynthetically active radiation in the lower layer increased in all treatments. Lactofen application increased the percent area covered and the number of phytosanitary products spray droplets per cm² in the middle and lower layers of the plants. The lower third of the plants experienced the greatest effect of the treatments with regard to the number of pods, grains and grain weight, with treatment T2 presenting significant increases. The use of lactofen as a growth inhibitor at the beginning of pod development in soybean caused changes to plant architecture and root development, consequently enhanced the productive efficiency of the plant, primarily due to increased grain production in the lower layer. Future research using lactofen in different phenological stages and cultivars may provide more insights in to the performance of this growth inhibitor in soybean

Foliar fortification of Copper (Cu) in Glycine max L. for the protection against Asian Soybean Rust (Phakopsora pachyrhizi Syd. & P.Syd.)

The Asian Soybean Rust caused by the fungus Phakopsora pachyrhizi is one of the serious phytosanitary problems faced by soybean [Glycine max (L.) Merrill], which cause up to 80% yield loss. An alternative for the integrated management of the disease is the use of mineral nutrition together with phytosanitary treatments. Thus, the objective of this study is to understand the effect of foliar fortification with copper (Cu) along with phytosanitary treatments in the soybean reaction to Rust by lignin content variation in leaf tissues, and how it reflects the yield. The experimental design was a randomized block with four replicates. Four concentrations Cu (30, 60, 90, 120 g Cu ha-1) were tested in two distinct sources (cuprous oxide and copper carbonate) together with phytosanitary treatments. Evaluations were made to determine the progression of Asian Rust severity, micronutrient content in leaves and grains, as well as lignin content in leaves. The grain yield components and productivity were also evaluated. The Cu contents in the soybean leaves and grains were influenced by foliar spraying. Foliar spray with Cu retarded the disease progression, reducing the severity of Asian Rust and positively impacting grain yield. The amount of lignin present in the leaves was altered considerably with the application of the Cu associated with phytosanitary treatments. The results suggest that the leaf nutrition with copper together with phytosanitary treatments, may reduce the rust severity and improvement the plant performance. Future research with Cu application and analysis of specific enzymes, secondary metabolites and cell wall thickness may further contribute to the understanding of the role of Cu in defence against Asian Soybean Rust

Root traits correlated with soybean yield in a subtropical region

Root system plays a crucial role in plants’ anchoring, water and nutrients acquisition and storage of carbohydrates. While it is understood that root system traits contribute to crop yield, little is known about the particular effects of root morphology over crop yield, even on major crops such as soybean (Glycine max). The objective of this study was to investigate if distinct soybean grain yield plants, grown at different sites, displayed differences in their root system morphology. This distinct traits in the root system should be responsible to the differences of yield, thus, showing which traits should be followed in breeding programs to develop higher yield cultivars. The soybean cultivar DM 5958 RSF IPRO was sowing in a randomized complete block design experiment. Treatments comprised three cultivation sites and five soybean grain yield classes. Plant emergence and root system morphology attributes were evaluated. Results showed that late emergence negatively influenced root development. A huge difference among sites over very thin (89%) and thin (85%) roots was found in the high yield class, and since the plants have similar yield, it appeared that the thin and very thin roots length have no impact on the yield, being influenced mostly by the environment. Forks and tips roots didn’t show a pattern. In contrast, roots volume only showed a 22% reduction, demonstrating to be less influenced by the environment, resulting in a greater correlation with the grain yield. Thus identified as the main attribute to be explored when seeking to select new soybean cultivars

Yield potential of grapevine cultivated under plastic cover

O objetivo deste trabalho foi avaliar a influência do uso de cobertura de plástico sobre os componentes do rendimento da videira (Vitis vinifera L.) cultivar Moscato Giallo. O experimento foi realizado nas safras 2005/2006 e 2006/2007, em Flores da Cunha, RS, em duas áreas de vinhedo, uma com cobertura de plástico impermeável e outra sem cobertura (controle). O microclima foi avaliado quanto à temperatura e umidade relativa do ar, radiação fotossinteticamente ativa e velocidade do vento próximo ao dossel vegetativo e aos cachos. A avaliação dos componentes de rendimento ocorreu em delineamento experimental inteiramente ao acaso, e foram identificadas dez plantas marcadas aleatoriamente em cada área. Avaliaram-se a produção por planta e por hectare, o número de cachos por planta e por metro quadrado, o número de sarmentos por metro quadrado, a massa e comprimento de cacho, a massa de engaço, o número de bagas por cacho, o diâmetro transversal de bagas e a relação entre massa de película e massa de polpa. A cobertura de plástico possibilita aumento na produtividade, não afeta a relação entre massa de casca e massa de polpa das bagas e favorece a estabilidade de produção, independentemente das condições meteorológicas no ciclo.The objective of this work was to evaluate the effect of plastic cover on the yield components of grapevine (Vitis vinifera L.) cultivar Moscato Giallo. The experiment was carried out in 2005/2006 and 2006/2007 crop seasons, in Flores da Cunha, RS, Brazil, in two vineyard areas, one covered with an impermeable plastic film and other without covering (control). The microclimate was evaluated in terms of air temperature, air relative humidity, photosynthetically active radiation and wind speed above canopy and close to clusters. The yield components were evaluated in a completely randomized design, in ten plants randomly selected in each area. Measures were made for production per plant, yield per hectare, clusters per vine, clusters per square meter, twigs per square meter, weight and length of clusters, weight of rachis, number of berries per cluster, diameter of berries, and skim/pulp ratio. Plastic cover promotes yield increases, does not affect pulp/skin ratio, and promotes production stability, independently of climate conditions in each season

Alterações micrometeorológicas em vinhedos pelo uso de coberturas de plástico

The objective of this work was to evaluate the effects of plastic covering on the microclimate of vineyards (Vitis vinifera L., cultivar Moscato Giallo), in Serra Gaúcha region in Rio Grande do Sul State, Brazil. The experiment was performed in Flores da Cunha, RS, during the 2005/2006 growing season. It comprised uncovered and covered rows of vines, using a 160 µm thick plastic film. Photossinthetically active radiation (PAR), air temperature and humidity, and wind velocity were monitored: over the plastic covering; between the film and the canopy; over the uncovered canopy; and close to grapes of both treatments. Reference evapotranspiration was estimated for both treatments. From the incoming PAR, 67.5% reached the covered canopy, 16% reached the covered grapes, and 36% reached the uncovered grapes. The plastic covering increased by 3.4ºC the maximum air temperatures close to plants. Diurnal air relative humidity was reduced, while water vapor pressure and vapor pressure deficit were increased because of the plastic covering, which also reduced in 88% the wind velocity in comparison to open air. The reference evapotranspiration on the covered canopy was 35% lower than in open air. Although increasing diurnal air temperatures, the plastic covering may reduce the evaporative demand on vineyards, by reducing the incoming solar radiation and the wind velocity.O objetivo deste trabalho foi avaliar os efeitos da cobertura de plástico sobre alguns elementos meteorológicos que formam o microclima de vinhedos de Vitis vinifera L., cultivar Moscato Giallo, em Flores da Cunha, na Serra Gaúcha. O experimento foi conduzido na safra 2005/2006, com os tratamentos: fileiras de plantas descobertas; e fileiras de plantas cobertas com plástico transparente tipo ráfia, com 160 µm de espessura. Medições contínuas de radiação fotossinteticamente ativa, temperatura e umidade do ar, e velocidade do vento foram realizadas: acima da cobertura; entre a cobertura e o dossel; sobre o dossel descoberto; e junto aos cachos de ambos tratamentos. Estimou-se a evapotranspiração de referência nos dois tratamentos. Da radiação fotossinteticamente ativa incidente, 67,5% chegou ao dossel coberto, 16% atingiu os cachos cobertos e 36% chegou aos cachos descobertos. A cobertura aumentou em 3,4°C as temperaturas máximas do ar junto às plantas. A umidade relativa do ar diurna foi menor, enquanto a pressão de vapor e o deficit de saturação foram superiores debaixo da cobertura. A velocidade do vento foi reduzida pela cobertura em 88%. No ambiente coberto, a evapotranspiração de referência foi 65% daquela do ambiente externo. Embora aumente as temperaturas diurnas, a cobertura de plástico promoveu redução na demanda evaporativa do vinhedo