A genetic complementation system was developed
in which tobacco etch virus (TEV) polymerase (NIb)-
expressing transgenic plants or protoplasts were inoculated
with NIb-defective TEV mutants. A β-glucuronidase (GUS)
reporter gene integrated into the genomes of parental and four
mutant viruses was used to assay RNA amplification. Two
mutants (termed VNN...
Satellite measurements allow global assessments of phytoplankton concentrations and, from observed temporal changes in biomass, direct access to net biomass accumulation rates (r). For the subarctic Atlantic basin, analysis of annual cycles in r reveals that initiation of the annual blooming phase does not occur in spring after stratification surpasses...
Pollination ecology may play an important role in the maintenance of selfing in populations of self-compatible hermaphroditic plants where both selfing and outcrossing occur (mixed mating). Behavior and abundance of pollinators can influence the two major modes of selfing; autogamy (selfing within a flower) and geitonogamy (selfing between flowers on...
Alaska-cedar (Chamaecvparis nootkatensIs (D. Don) Spach) is a
valuable tree that is suffering from a serious decline and mortality of
unknown cause throughout southeast Alaska. Epidemiological and
pathological studies were initiated to determine if a pathogen is the
primary cause of this problem. By examining old aerial photographs and
by...
Developmental changes in the storage organ of Brassica
campestris L. were followed from the organization of the embryonic
radicle and hypocotyl to the mature storage organ. Three independent
primary meristems gave rise to the cortex, the stele, and the
root cap-epidermis. The primary development is typical of the
Cruciferae. Cambial...
A rapid and reliable assay is needed to evaluate hop
resistance to Verticillium wilt caused by Verticillium
dahliae. Assays used in the past are laborious, require
long incubation periods, and usually produce mild symptoms
which are difficult to evaluate and are often not
consistent. A study comparing several methods for...
The Pacific Coast form of Douglas-fir in natural forest succession
is an intermediate species thriving in the Coast Range and
Cascade Mountains of the Pacific Northwest. This species constitutes
26 percent of the standing timber in the United States, and 24 percent
of the nation's annual timber harvest. Characteristics of...
Sand dunes are found along the coasts of most of the large land
masses of the world. Because of their proximity to man and his
activities, the maritime sand dunes of Europe, particularly Germany,
France, Holland and Scandinavia, have the longest history of stabilization
activities and botanical investigation. There are...
A new photosystem-II mutant of the green alga Scenedesmus
obliquus D₃, strain PS-28, has been shown to lack a-tocopherol
(vitamin E). The photosynthetic activity of dark grown samples of
PS-28 is about 20% of the wild-type control. Culturing the mutant
at low light intentisites (10⁴ ergs/sec-cm ²) stimulates photosynthetic
activity...
The ectomycorrhizal fungi Cenococcum geophilum, Hebeloma
crustuliniforme and Laccaria laccata produced ethylene in vitro in
modified Melin-Norkrans liquid medium only if amended with 2.5 to
10 mM methionine; Pisolithus tinctorius failed to produce ethylene
unless the cultures were renewed with fresh methionine-amended
medium prior to ethylene assay. An additional 19...