Pioneer species are fast-growing, short-lived gap exploiters. They are prime candidates for neutral dynamics because they contain ecologically similar species whose low adult density is likely to cause widespread recruitment limitation, which slows competitive dynamics. However, many pioneer guilds appear to be differentiated according to seed size. In this paper, we compare predictions from a ...

1. Ambrosia trifida L. (giant ragweed), an aggressive weed of US grain crops and indigenous to North America, colonizes no-tillage crop fields and undisturbed soils despite its large seed size and susceptibility to seed predation. Secondary seed dispersal is critical to seed survival and seedling establishment, yet mechanisms of secondary dispersal are poorly understood for such large-seeded we...

The role of ungulate grazing in shaping rangeland ecosystems is well known relative to other important plant-animal interactions such as pollination, seed dispersal, granivory, and belowground herbivory. Successful rangeland revegetation may be enhanced by strategies that favor certain groups of animals and discourage others. Many perennial forbs and shrubs require animals for successful pollin...

Regulation of seed germination requires coordinate action by the embryo and surrounding endosperm. We used Arabidopsis thaliana to establish the relative roles of embryo and endosperm in the control of seed germination and seedling establishment. We previously showed that endospermic oil reserves are used postgerminatively via gluconeogenesis to fuel seedling establishment and that lipid breakd...

BACKGROUND AND AIMS Parkinsonia aculeata (Caesalpinaceae) is a perennial legume with seeds that have hard-seeded (physical) dormancy and are potentially very long-lived. Seed dormancy is a characteristic that can both help maximize the probability of seedling establishment and spread the risk of recruitment failure across years (bet-hedging). In this study, dormancy-release patterns are describ...

Ghana’s seed sector has undergone some significant changes in the past few years, including the establishment of a new seed law and regulations, the appointment of a National Seed Council, and the emergence of a more diversified commercial seed sector. This paper begins by reviewing the principal elements in Ghana’s commercial seed sector. It then examines three factors that will be critical to...

Poor emergence resulting in inadequate stand establishment is a major problem associated with direct-seeded rice production, especially for semidwarf cultivars. In order to gain information on the problem, plant type related to gibberellic acid (GA3) and seeding depth was studied. A total of 21 cultivars including 9 semidwarfs and 12 talls had seed treated with GA3 at 25 parts per million (ppm)...

There is increasing interest among growers in novel establishment systems for cover crops that can rehabilitate and protect soil. Cropping intensification has led to yield declines, compacted and poor quality soil, and increased pest problems. Cover crops in the Brassica (mustard) family offer benefits in soil conservation, improvement in soil quality, reduction in nitrate leaching, and suppres...