Caracterização morfológica de frutos, sementes e plântulas e, germinação de sementes de Euphorbia hyssopifolia Lam

Abstract

Euphorbia hyssopifolia Lam., is a feared species, occurring in annual crops, which can cause losses of more than 80% in productivity, occupying the most varied types of vegetation and habitats. The objective of this work was the physical and morphological characterization of Euphorbia hyssopifolia fruits and seeds, recording the different stages of post-seminal development, as well as studying the physiological potential of seeds as a function of temperature, light, amount of water and time. burial in the ground. For the physical characterization, eight repetitions of one hundred seeds and fruits were weighed and the weight of one thousand seeds determined, number of seeds per kilogram, and measures of central tendency were calculated for each variable. In the morphological characterization, the type, size and location of the embryonic axis were verified, as well as the location of the micropyle, funiculus and reserve material. In post-seminal development, the germination process was recorded for twenty days and weighed daily to record water absorption. After the period of the germination process, the seedlings were cut in the transition region called the collar, in order to carry out the study of the regrowth capacity. In addition to these, the germination behavior of seeds (mature and immature) was studied as a function of constant temperatures of 20°C, 25°C, 30°C, 35°C and alternating 20-30°C in the absence and presence of light, adopting the factorial scheme 5 x 2 (temperature x light regime), analyzing the variables: Percentage, speed, average time. relative frequency of seed germination and seedling length; of water volume (1.5; 2.0; 2.5; 3.0) in a 2 x 4 factorial scheme (maturation condition x water volume), seed burial time in the soil, longevity in water submersion and high temperatures (80oC, 100oC, 120oC and 140oC) in the physiological potential of the same, in the time intervals of one and five minutes, being analyzed: Percentage, speed, average time. The experimental design was completely randomized, with four replications of 25 seeds for each treatment. According to the results obtained, it was verified that the weight of a thousand seeds was on average 4.04mg, corresponding to approximately 250.000.000 seeds/kg. The dimensions of the fruits and seeds showed little variation between them, with a humidity of 10%. The seed is testal and the embryo is of spatulate leaf-like subdivision. The germination is epigeal and its seedling is of the phanerocotyledonary type. Seedlings did not show regrowth capacity after being cut in the collar region. The highest percentage and speed of germination was obtained at the alternating temperature of 20-30oC, in the presence of light. Its viability is rapidly lost after burial in soil, submersion in water and when exposed to high temperatures. These environmental conditions drastically affect its germination capacity and are relevant for the management of the species in agricultural areas. Such results obtained in this present study are proposed for inclusion in the Rules for Seed Analysis (RAS).

Keywords: Seed germination. Ecophysiology of germination.