Seed size is an important indicator of physiological quality, since it may affect seed germination and seedling growth, especially under stress conditions. This study aimed to investigate the effects of seed size on germination and initial seedling growth, under salinity and water stress conditions. The treatments were arranged in a completely randomized design, in a 3 × 3 factorial scheme: three seed size classes (small, medium and large) and three stress treatments (control, saline or water stress), with four replicates. Water and salt stresses do not reduce the germination rate of medium and large seeds; however, the germination rate of small seeds is reduced under salt stress conditions. Drought stress drastically reduces the shoot growth of seedlings regardless of seed size, whereas root growth is higher in seedlings from medium and large seeds under water stress conditions. Under non-stressful environments, the use of large seeds is preferable, resulting in more vigorous seedlings with a greater dry matter accumulation. Medium-size seeds are more adapted to adverse environmental conditions and, therefore, should be used under conditions of water shortage and salt excess in the soil at sowing time. Seedlings are more tolerant to salinity than to water stress during the germination stage and initial growth under laboratory conditions.

The economic and scientific interest in Hancornia speciosa Gomes (mangabeira) has increased in recent years, especially due to the commercialization of its fruits and the extraction of natural compounds with high pharmacological potential. This paper aims to determine and correlate the main physical and biometric characteristics of fruits and seeds of mangaba tree, as well as identifying the most appropriate substrate for the seedling emergence test. The following physical and biometric traits were measured in 100 fruits and 100 seeds: longitudinal diameter, transverse diameter, thickness, fresh mass, pulp fresh mass, volume, number of seeds. To identify the best substrate, a completely randomized design with two treatments (substrates) and ten replications of 20 seeds was used. The evaluated substrates were: sand and commercial substrate (Plantmax HT®). The shoot height, root length, stem diameter, total dry mass, and the relation between shoot height and stem diameter were evaluated at 50 days after sowing. Mangaba fruits and seeds showed great variations in their biometric traits, in addition to significant and positive correlation predominant in most characteristics. High fruit pulp yield can be optimized with the selection of plants with fruits show greater fresh mass due to the high degree of association between this characteristic and pulp yield. The use of the commercial substrate resulted in higher shoot height, greater number of leaves, and higher shoot height/stem diameter ratio.

The effects of water and salt stress on rate of germination and seedling growth were investigated under laboratory conditions in 46 soya bean genotypes from Central-West region of Brazil to verify how these stresses may limit crop establishment during the initial growth stage and also to identify the most tolerant genotypes to drought and salinity. Mild water and salt stresses were imposed by seed exposure to-0.20 MPa iso-osmotic solutions with polyethylene glycol-PEG 6000 (119.57 g/L) or NaCl (2.357 g/L) for 12 days at 25°C. The germination percentage, seedling length and seedling dry matter were measured, and then, salt or drought tolerance indexes were calculated.

A quality substrate is essential to ensure the proper conditions for the emergence and early development of seedlings. The aim of the present study was to evaluate different proportions of termite mound substrate in the emergence and early development of tomato seedlings. The experiment was performed in a completely randomized design, with five treatments constituted by the substrates, with four replications: T 1 : Washed sand (100%); T 2 : Washed sand (75%) + termite mound material (25%); T 3 : Washed sand (50%) + termite mound material (50%); T 4 : Washed sand (25%) + termite mound material (75%) and T 5 : termite mound material (100%). The Santa Clara cultivar (tomato) of Topseed ® was used. The seeds were distributed in gerbox boxes. Emergence, emergence speed index, shoot height, number of leaves, shoot dry mass, root length and root dry mass of tomato seedlings development were evaluated after 25 days. The use of termite mound substrates is a viable alternative to the emergence and development of tomato seedlings. In general, the substrate of termite mound material (100%) was the most promising in the increment of all variables.

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