Seed dormancy, germination, emergence and seed longevity in Galinsoga parviflora and G. quadriradiata

Abstract

Summary Galinsoga quadriradiata (hairy galinsoga) and Galinsoga parviflora (smallflower galinsoga, gallant soldier) are very troublesome weeds in many vegetable row crops in Europe. To optimise management strategies for Galinsoga spp. control, an in‐depth study of germination biology was performed. Germination experiments were conducted to evaluate the impact of light and alternating temperatures on germination of a large set of Galinsoga populations. Seedling emergence was investigated by burying seeds at different depths in a sandy and sandy loam soil. Dormancy of fresh seeds harvested in autumn was evaluated by studying germination response in light at 25/20°C with and without nitrate addition. Seed longevity was investigated in an accelerated ageing experiment by exposing seeds to 45°C and 100% relative humidity. Galinsoga spp. seeds required light for germination; light dependency varied among populations. Seedling emergence decreased drastically with increasing burial depth. Maximum depth of emergence varied between 4 and 10 mm depending on soil type and population. In a sandy soil, emergence percentages were higher and seedlings were able to emerge from greater depths than in a sandy loam soil. Freshly produced G. parviflora seeds, harvested in autumn, showed a varying but high degree of primary dormancy and were less persistent than G. quadriradiata seeds that lack primary dormancy. Lack of primary dormancy of freshly harvested G. quadriradiata seeds and light dependency for germination may be used to optimise and develop Galinsoga management strategies.

Effects of environmental factors and burial depth on seed germination and emergence of two populations of Caucalis platycarpos

“…Environmental conditions, seed dispersal and germination and seedling growth are the main factors affecting plant species distribution (Chauhan & Johnson, ; Ahmed et al ., ). Seed germination responses to environmental factors, such as temperature, light, osmotic potential and salt stress, could affect the establishment of a plant species (De Cauwer et al ., ; Wu et al ., ). Seed burial depth and crop residue as mulch could also affect weed seedling emergence and establishment within a cropping system (Ahmed et al ., ).…”

Reduction in field emergence and seedbank density of Galinsoga quadriradiata and other weeds after contrasting false seedbed strategies in organic vegetable fields

“…These results may be explained by the higher weed control efficacy of flame weeding following the fifth pass in experiment 2, and the absence of soil disturbance that avoids movement of viable seeds into the germination zone. Long‐term lack of redistribution of viable seeds with flame weeder use may lead to the steady depletion of seedbanks in the shallow germination zone of G. quadriradiata (upper 4–12 mm of topsoil; De Cauwer et al ., ) and P. annua (upper 15 mm of topsoil; Peachey et al ., ), thus reducing the potential number of emergent seedlings during the crop growing season.…”

“…1), in contrast to P. annua and Stellaria media seedlings. Unlike P. annua and S. media, which have a minimum germination temperatures of 2-5°C (Warwick, 1979) and 4°C (Van der Vegte, 1978), respectively, G. quadriradiata is a thermophilic species with a minimum and optimal germination temperature of about 10°C and day/night temperatures of 24-25/18-20°C (De Cauwer et al, 2014). It is likely that soil moisture content in the period between 11 April and 10 May, when there was just 19.6 mm of precipitation, was suboptimal for seed germination.…”

“…are compromised, due to the presence of a dense and shallow root system with multiple secondary and adventitious roots (Canne, 1977). Moreover, both species are prolific and may produce several generations per year (Riemens & van der Weide, 2008;De Cauwer et al, 2014). Control of these weeds is only achievable through intensive weed control that comprises several iterations.…”

Improving Small Weed Seeds Viability Assessment Using Tetrazolium Test

“…Weeds aggressiveness characteristics highly contributes to plants interference processes, impairing crops development. A part of this characteristic is related to seeds production and physiological behavior, including the high number of propagules formed, dissemination mechanisms and seed dormancy, which enable asynchronous germination (Cauwer et al, 2014). Weeds producing thousands seeds per plants are often found, resulting in increased difficulties on their control within farming areas and increasing the soil seed bank (SSB).…”