Mature seeds of Helianthus annuus L. exhibit dormancy that is eliminated during storage in dry conditions. In vitro culture of immature embryos isolated at different times after anthesis showed that the youngest embryos are able to germinate, but within the third week after pollination, dormancy progressively affected most of the embryos. A radioimmunoassay showed that the endogenous abscisic a...

The effect of soil salinity on the growth and competition among Helianthus paradoxus, H. annuus, and H. petiolaris was examined in a greenhouse experiment to determine the role competition might have in leading to the narrow endemism of H. paradoxus. Helianthus paradoxus (the Pecos sunflower or puzzle sunflower) is a threatened annual species that is federally listed and only found in a few are...

Leaf defenses are widely recognized as key adaptations and drivers of plant evolution. Across environmentally diverse habitats, the macroevolution of leaf defenses can be predicted by the univariate trade-off model, which predicts that defenses are functionally redundant and thus trade off, and the resource availability hypothesis, which predicts that defense investment is determined by inheren...

Beni Tal* and David J. Robeson A RCO Plant Cell Research Institute, 6560 Trinity Court, Dublin, CA 94568—2685, USA Z. Naturforsch. 41c, 1032—1036 (1986); received July 16/August 12. 1986 Pyrenocine A, Phytotoxin, Fungal M etabolite, Alternaria, Helianthus tuberosus A previously undescribed species of Alternaria was isolated from the leaves of Helianthus tuberosus bearing necrotic lesions. W hen...

In spite of the economic importance of powdery mildew on cucurbits, literature and databases about the fungal species reveal different species numbers and names, often indicating only two species, with inconsistent host specificities for different members of Cucurbitaceae. Revision of the available literature indicates the presence of at least six species of powdery mildews on Cucurbitaceae wit...

In present investigation, the seeds of Helianthus annuus L. variety Modern were treated with nine different concentrations (0.05%, 0.25%, 0.50%, 0.75%, 1.00%, 1.25%, 1.50%, 1.75% and 2.00%) of caffeine to raise the M1 generation and the effect of caffeine on seedling height on 30 th day of sowing, mature plant height, days to maturity and yield parameters was observed. Generally, the lower dose...

In recent decades allelopathy has gained much attention in the sustainable agricultural systems. It is necessary to trace out the mechanism of action of allelochemicals of plants on other plants. Allelochemicals of different plants interact differently with each other. In the present context an attempt has been made to study the influence of allelochemicals released by Parthenium on the growth,...