The new U.S. measurement standard for the air-kerma strength from low-energy photon-emitting brachytherapy seed sources is formally described in detail. This instrument-based standard was implemented on 1 January 1999, with its salient features and the implications of differences with the previous standard given only through a series of informal communications. The Wide-Angle Free-Air Chamber (...

1 We present results from a long-term sowing experiment conducted in nutrient-poor savanna grassland in eastern Minnesota. We examine the effects of a one-time seed addition of 23 grassland species on plant community dynamics and structure over eight growing seasons. 2 Our goals were to: (i) test the importance of seed availability in regulating plant colonization dynamics and species richness;...

Agents responsible for tosses of conifer seed and methods for seed protection are reviewed. Published information indicates that much seed is destroyed, especially by seedeating rodents and birds. Improvement of existing protective methods and development of new chemical means are necessary to overcome the problem.

This paper considers strengths and weaknesses of the informal and formal seed as a basis for seed sector development. The informal seed sector is defined as the total of farmers’ seed production, selection and seed exchange activities. Farmers play an important role in seed supply but they are generally not considered as a partner in the seed sector. Seed produced by farmers is still the most i...

Ð Although there has been a considerable growth of private seed enterprises in developing countries, there are few examples of the private delivery of seed of public crop varieties that are not hybrids. This paper discusses the example of rice in Andhra Pradesh, where private enterprise is supplying an increasing proportion of the seed used by farmers. The institutional conditions for private e...

Successful crop production depends initially on the availability of high-quality seed. By 2050 global climate change will have influenced crop yields, but will these changes affect seed quality? The present review examines the effects of elevated carbon dioxide (CO2) and temperature during seed production on three seed quality components: seed mass, germination and seed vigour. In response to e...

Dormancy is a state of metabolic arrest that facilitates the survival of organisms during environmental conditions incompatible with their regular course of life. Many organisms have deep dormant stages to promote an extended life span (increased longevity). In contrast, plants have seed dormancy and seed longevity described as two traits. Seed dormancy is defined as a temporary failure of a vi...

The timing of harvest is a major factor affecting seed quality in soybean, particularly in Midsouthern USA, when rain during harvest period is not uncommon. The objective of this research was to evaluate the effects of time of harvest on soybean seed quality (seed composition, germination, seed coat boron, and lignin) in high germinability (HG) breeding lines (50% exotic) developed under high h...

Seed weight is a very important and complex trait in rapeseed (Brassica napus L.). The seed weight of rapeseed shows great variation in its natural germplasm resources; however, the morphological, cytological and genetic causes of this variation have remained unclear. In the present study, nine highly pure inbred rapeseed lines with large seed weight variation and different genetic backgrounds ...

abstract a sub-sample of lentil (lens culinaris medik. cv. kimia) seeds was kept as bulk (s1) and another sample was separated to large (s2) and small (s3) seeds. a sub-sample of each size was kept as control or high vigor seed lot (a1) and the two other sub-samples were artificially aged for 2 and 4 days (a2 and a3, respectively). field performance and some physiological traits of plants from ...