The objective in this review was to discuss the importance of maize currently and the crucial role it may play in the future for food production in scenarios of water shortage, as well as the importance of conserving its landrace cultivars, which have a considerable portion of the reserve of genetic variability. Maize plants, when exposed to water deficit, may develop physiological, morphological, biochemical and anatomical adaptation mechanisms. With the aid of genetic improvement, characteristics that impart tolerance are fixed in plants through conventional methods. In this context, ‘Tuxpeño Sequia’ cultivars were developed in Mexico, while in Africa, one of the most important strategies was the development of ‘DT’ (Drought-tolerant) cultivars. In the United States, one of the most important processes was the development of PionerAquamax® hybrids, while in Brazil, it was the development of cultivars with the ‘Maya Latente’ gene. Through genetic transformation, the hybrid ‘MON 87460’ was developed. However, it should be mentioned that, for a cultivar to be well accepted by producers, besides having one or more adaptation characteristics, it must have a high grain yield. Biotechnological tools such as the use of molecular markers, genetic transformation, and modeling through bioinformatics, associated with conventional selection, will be fundamental to guarantee the advancement of water deficit tolerance in maize.

This study aimed to obtain equations to estimate leaf area from linear leaf dimensions and establish the allometric relationship between leaf area and the number of leaves on the main stem of chia (Salvia hispanica L.) at different sowing times. The experiment was conducted in the agricultural year 2016/2017 on five sowing times in Santa Maria, RS, Brazil, in a randomized block design with four repetitions. In each plot, ten random plants were marked weekly during the vegetative phase to determine the number of leaves (NL) in the main stem, and three of these for the determination of leaf area (LA). A total of 70 leaves of different sizes were used to calibrate the model. Another 106 leaves were used to test the predictive capacity of the equations by various statistical indices. The length (L) and the largest leaf width (W) were measured. Leaf collection was carried out during the cycle, in all sowing times to represent all leaf sizes. The linear, quadratic, exponential, and potential models were adjusted. The non-destructive method, through the linear dimensions of the leaf, is appropriate for estimating the leaf area in chia. The general equation LA = 0.642 (L x W) can be used to estimate the leaf area of the chia plants without loss of precision. The potential model is appropriate to characterize the allometric relationship between leaf area evolution and the number of leaves accumulated in the main stem of chia at different sowing times.

The objective of this study was to create a single mathematical equation able to estimate the leaf area of different cassava cultivars from one lineal dimension without destroying any plant tissue. Two hundred leaves per cultivar from ten cultivars were used to calibrate the model and more than one hundred leaves per cultivar were used to test its predictive capacity as independent data. All equations were the result of the nonlinear correlation between the leaf area and the length of its central lobe. To validate it as a “general” equation, another set of five cultivars were used. A “specific” equation for each cultivar was also calibrated to compare with the “general” equation’s performance. Cultivar Vassourinha has remarkably different leaf morphology from the other nine cultivars, making the “general” equation’s tendency line deviate and lowering its coefficient of determination. Therefore, one more equation was generated excluding that cultivar and, as a result, it was not possible to estimate the leaf area from all the cultivars using only the “general” equation. The “general without Vassourinha” equation has a high accuracy level when estimating leaf area of the other nine cultivars, plus the extra five cultivars that were included to validate the general equation; all of them present similar leaf morphology. Due to its importance, Vassourinha cultivar’s “specific” equation should be used when estimating leaf area for this cultivar or other cultivars with similar leaf morphology.

Os objetivos deste trabalho foram avaliar a resposta à adubação e diferentes épocas de controle de plantas daninhas no acúmulo de matéria seca de folhas, hastes, raízes e produção de massa fresca de raízes de mandioca. Dois experimentos foram conduzidos em campos comerciais nos municípios de Ibarama e Santa Maria localizados no Rio Grande do Sul, Sul do Brasil, durante a safra 2018/2019. Cinco tratamentos, com aplicações variadas de fertilizantes químicos e herbicidas foram utilizados para representar as práticas de manejo comumente utilizadas pelos agricultores do Sul do Brasil. O modelo baseado no processo Simanihot foi usado para simular o crescimento, desenvolvimento e produtividade da mandioca sob condições potenciais. Os resultados mostram que a dose recomendada de fertilizantes e calagem combinados com herbicida pré-emergente e três manejos mecânicos de limpeza de plantas daninhas apresentaram um aumento de 72% na produtividade de raízes em relação ao manejo utilizado pela produtividade média dos pequenos agricultores. Portanto, é possível atingir 80% do potencial de produtividade mantendo a cultura da mandioca livre de interferência de plantas daninhas e com aplicação de fertilizantes. A presença de plantas daninhas durante os primeiros 100 dias após o plantio reduziu cerca de 50% da produção de matéria seca da planta em Ibarama e Santa Maria e 79,2% da produtividade de raízes frescas em Ibarama.

The aim of this study was to identify plastochron phases in soybean cultivars with determinate and indeterminate growth habits. Experiments were conducted from 2010/2011 to 2022/2023 at four locations in Rio Grande do Sul state (RS), Brazil, using 25 soybean cultivars with determinate (6) and indeterminate (19) growth habits. This study divided the plastochron into phases during the soybean node emission stage. In irrigated cultivars with a determinate growth habit, the plastochron has an early and late phase of 59.7 and 65.7 °C day node^-1, respectively. In rainfed (non-irrigated) environments, there is no difference between the early and late plastochron phases. The early and late plastochrons of irrigated cultivars with an indeterminate growth habit are 64.1 °C day node^-1, while the intermediate phase is 58.5 °C day node^-1. In rainfed environments, the average value of the early and intermediate phases is 60.6 °C day node^-1, with a late plastochron of 79.4 °C day node^-1. Dividing the plastochron into phases during node emission, as proposed in this study, improves understanding of vegetative development in soybean cultivars with determinate and indeterminate growth habits and establishes ecophysiological foundations for chronological function construction.

A maioria das cultivares semeadas no Sul do Brasil apresentam grupo de maturidade relativa (GMR) entre 4.5 e 7.0 e tipo de crescimento indeterminado. O objetivo do estudo foi detalhar o desenvolvimento vegetal, através do plastocrono e número final de folhas (NFF), de cultivares com diferentes GMRs e épocas de semeadura. Foram utilizadas 11 cultivares de soja com GMR variando de 4.2 a 8.2 e tipo de crescimento determinado e indeterminado em três anos agrícolas. Foram contados o número de nós visíveis e avaliado os estádios vegetativos três vezes por semana. O NFN varia de acordo com o fotoperíodo em que a planta é exposta na fase vegetativa e difere entre cultivares, de acordo com o GMR e tipos de crescimento, sendo os menores valores observados em semeaduras precoces (setembro) e tardias (janeiro e fevereiro).