Temperatura cardeal e potencial hídrico na germinação de sementes de corda-de-viola (Ipomoea triloba)

Abstract

O presente trabalho teve como objetivos avaliar o efeito da temperatura e da umidade na germinação e na emergência de corda-de-viola (Ipomoea triloba) e determinar o efeito de potenciais hídricos e de temperaturas na germinação de sementes e na elongação do hipocótilo e da radícula dessa espécie. Avaliaram-se os termoperíodos de 9,3 e 5 (7,5); 14,3 e 10 (12,5); 19,3 e 15 (17,5); 24,3 e 20 (22,5); 29,3 e 25 (27,5); 34,3 e 30 (32,5); 39,2 e 35 (37,5) e 44,2; 40 (42,5); e 49,2 e 45 (47,5) ºC, alternando-se durante 14 e 10 horas, e os potenciais hídricos de 0, -0,03, -0,06, -0,1, -0,2, -0,4, -0,6 e -0,9 MPa. A germinação de corda-de-viola foi descrita pela interação da temperatura e do potencial hídrico, e a taxa de elongação da radícula e do hipocótilo, em função da temperatura. Os parâmetros do modelo usado para estimar as temperaturas cardeais e o potencial hídrico base foram determinados por "probit" análise, para a germinação. Em se tratando dos processos de elongação, as temperaturas cardeais foram determinadas por regressão linear, e suas respostas à temperatura, descritas por equação de regressão de segunda ordem. Os modelos matemáticos usados descreveram os processos de germinação e elongação do hipocótilo e da radícula dessa espécie em termos de tempo hidrotérmico e temperatura, respectivamente.

Weed emergence in autumn under temperate conditions

“…Average air temperatures registered during the observation periods of the number of The interaction of temperature with soil moisture Grundy & Mead, 2000;Rizzardi et al, 2009;Gardarin et al, 2010), mainly the highest temperatures in the indicated interval of values, with the highest soil moisture, favoured plant emergence. In addition, maintenance of the average temperature between the mentioned values (mild temperature conditions) associated with soil moisture tending to field capacity, makes it possible for the potential population to appear faster, thus, according to Spitters (1989), Silva et al (2009) and Yamashita & Guimarães (2010) less time is necessary for obtaining a given germination percentage.…”

“…According to Hadas (1982), Baskin et al (1993) and Rizzardi et al (2009), water, from rainfall or other sources, is necessary to ensure the seeds' hydration. Seeds require sufficient water for absorption and consequent germination (Hadas, 1982;Bradbeer, 1988;Bradford, 1990;Silva et al, 2009;Yamashita & Guimarães, 2010).…”

“…There are many seeds which germinate well when supplied with excess water, however in others the excess of water reduces the tegument permeability and restrains germination (Bradbeer, 1988). The soil's environmental conditions, such as temperature Rizzardi et al, 2009;Gardarin et al, 2010), water, air composition (oxygen, carbon dioxide, water vapour and ethylene) and the quality of light, are essential for the beginning and continuation of the growth cycle of vegetal species, particularly with regard to seed germination and emergence of plants. In the natural environment each of these factors varies based on climatic elements, such as rainfall and radiation, which can not be directly controlled by humans.…”

“…In addition to rainfall, temperature is also important in the emergence of weed plants Myers et al, 2004;Rizzardi et al, 2009) as well as the moisture level of the topsoil (Gardarin et al, 2010). Thus, as a result of complex interactions, the species are able to enter into and remain in agricultural environments, and can expand in these habitats (Martínez-Ghersa et al, 2000).…”

Recovery and germinative response of Amaranthus deflexus L. seeds under different levels of water stress and luminosities

“…in water deficit induced by the increase in PEG 6000 concentrations in the substrate solution was responsible for a tendency of reduction in the mean values of TG and IV in the photoperiod of 12 light hours (Figure 2) Rizzardi et al (2009),. studying the germination of Ipomoea triloba L., an extremely aggressive weed species,observed a reduction of metabolic processes during germination…”