Crescimento e desenvolvimento de Conyza bonariensis em razão do acúmulo térmico e fotoperíodo

The objective of this work was to characterize the growth and development of hairy fleabane (Conyza bonariensis) according to thermal accumulation and photoperiod, at different sowing times, and to propose a scale representing the main plant development stages. The experiment was carried out with ten replicates in the 2011/2012 growing season. The sowing dates were: 05/31/2011, 07/04/2011, 08/03/2011, 09/09/2011, and 11/07/2011. Plant height (cm) and phenology were evaluated weekly. The duration of the different stages (days) and thermal time accumulation (°C day) were determined. The linear regression analysis showed that plant height was related to thermal time accumulation. Regardless of the sowing date, the vegetative stage had a longer duration (in days and in ºC day) than the reproductive stage. Sowing on 11/07/2011 promoted the shortening of the vegetative stage, and the rosette stage did not occur. Flowering was induced in the photoperiod between 12.5 and 13.5 hours of light, regardless of the sowing date. Slow growth was observed at lower temperature conditions, when plants accumulated 30.9 and 16.3°C day per centimeter of height for the 05/31/2011 and 11/07/2011 sowing dates, respectively. The phenology scale adequately predicts the development stages of hairy fleabane. O objetivo deste trabalho foi caracterizar o crescimento e o desenvolvimento da buva (Conyza bonariensis) em razão do acúmulo térmico e do fotoperíodo, em diferentes épocas de semeadura, e propor uma escala para representar os principais estádios de desenvolvimento das plantas. O experimento foi realizado com dez repetições, no período de cultivo 2011/2012. As datas de semeaduras foram: 31/05/2011, 04/07/2011, 03/08/2011, 09/09/2011 e 07/11/2011. A altura de planta (cm) e a fenologia foram avaliadas semanalmente. A duração dos diferentes estádios (dias) e a soma térmica acumulada (°C dia) foram determinadas. A regressão linear mostrou que a altura de plantas relacionou-se à soma térmica acumulada. Independentemente da data de semeadura, a fase vegetativa teve maior duração (em dias e em ºC dia) do que a fase reprodutiva. A semeadura em 07/11/2011 promoveu o encurtamento da fase vegetativa, e o estádio roseta não ocorreu. Houve indução do florescimento em fotoperíodo entre 12,5 e 13,5 horas de luz, independentemente da época de semeadura. Observou-se crescimento mais lento na condição de menor temperatura, em que as plantas acumularam 30,9 e 16,3 °C dia por centímetro de altura, nas semeaduras em 31/05/2011 e 07/11/2011, respectivamente. A escala fenológica prevê adequadamente as fases de desenvolvimento da buva

Comparação da Produtividade de Soja Observada e Simulada pelo Modelo Soysim para Seis Municípios do Rio Grande do Sul

A produtividade da cultura da soja foi simulada por um modelo ecofisiológico e comparada com dados de produtividade observada de seis municípios do Rio Grande do Sul – RS. As simulações foram realizadas através do modelo SoySim, com quatro datas de semeadura, três grupos de maturação e três níveis tecnológicos distintos

Transpiration and leaf growth of potato clones in response to soil water deficit

Potato (Solanum tuberosum ssp. Tuberosum) crop is particularly susceptible to water deficit because of its small and shallow root system. The fraction of transpirable soil water (FTSW) approach has been widely used in the evaluation of plant responses to water deficit in different crops. The FTSW 34 threshold (when stomatal closure starts) is a trait of particular interest because it is an indicator of tolerance to water deficit. The FTSW threshold for decline in transpiration and leaf growth was evaluated in a drying soil to identify potato clones tolerant to water deficit. Two greenhouse experiments were carried out in pots, with three advanced clones and the cultivar Asterix. The FTSW, transpiration and leaf growth were measured on a daily basis, during the period of soil drying. FTSW was an efficient method to separate potato clones with regard to their response to water deficit. The advancedclones SMINIA 02106-11 and SMINIA 00017-6 are more tolerant to soil water deficit than the cultivar Asterix, and the clone SMINIA 793101-3 is more tolerant only under high solar radiation

Transpiration and leaf growth of potato clones in response to soil water deficit

Potato (Solanum tuberosum ssp. Tuberosum) crop is particularly susceptible to water deficit because of its small and shallow root system. The fraction of transpirable soil water (FTSW) approach has been widely used in the evaluation of plant responses to water deficit in different crops. The FTSW 34 threshold (when stomatal closure starts) is a trait of particular interest because it is an indicator of tolerance to water deficit. The FTSW threshold for decline in transpiration and leaf growth was evaluated in a drying soil to identify potato clones tolerant to water deficit. Two greenhouse experiments were carried out in pots, with three advanced clones and the cultivar Asterix. The FTSW, transpiration and leaf growth were measured on a daily basis, during the period of soil drying. FTSW was an efficient method to separate potato clones with regard to their response to water deficit. The advancedclones SMINIA 02106-11 and SMINIA 00017-6 are more tolerant to soil water deficit than the cultivar Asterix, and the clone SMINIA 793101-3 is more tolerant only under high solar radiation

Performance of soybean in hydromorphic and nonhydromorphic soil under irrigated or rainfed conditions

O objetivo deste trabalho foi avaliar o cultivo de soja em solo hidromórfico ou não hidromórfico, com ou sem irrigação suplementar. Experimentos em campo com as cultivares TECIRGA 6070RR e A 6411RG foram realizados em terras altas (solos não hidromórficos) e em terras baixas (solos hidromórficos), que são tradicionalmente cultivadas com arroz irrigado. Determinaram-se, nas duas cultivares de soja, os seguintes parâmetros: índice de área foliar, estágios de desenvolvimento, partição de matéria seca e quantificação das trocas gasosas em nível foliar. Pequenos estresses hídricos, que comumente ocorrem por deficit ou excesso em áreas de soja cultivada em solo hidromórfico, não influenciam o desenvolvimento e a partição de matéria seca; porém, provocam reduções da condutância estomática, da taxa fotossintética e da evolução da área foliar. O cultivo de soja em solos hidromórficos faz com que as plantas sejam expostas ao estresse hídrico, até mesmo em anos com precipitação de chuvas bem distribuída ao longo da estação de crescimento, em razão da baixa capacidade de armazenamento de água desses solos.The objective of this work was to evaluate soybean cultivation in a hydromorphic or nonhydromorphic soil, with or without supplemental irrigation. Field experiments were carried out with the TECIRGA 6070RR and A 6411RG cultivars in highlands (nonhydromorphic soils) and lowlands (hydromorphic soils), which are traditionally cultivated with irrigated rice. The following parameters were determined in both soybean cultivars: leaf area index, developmental stages, dry matter partition, and leaf gas exchange. Low water stresses, which commonly occur either by deficit or excess in soybean areas cultivated in hydromorphic soils, do not affect the development and partitioning of dry matter; however, they cause reductions in stomatal conductance, photosynthetic rate, and leaf area evolution. Growing soybean in lowlands exposes plants to water stress, even in years with well-distributed rainfall during the growing season, due to the low water storage capacity of these soils