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...

UNLABELLED • PREMISE OF THE STUDY Evolutionary changes in how flowering time responds to photoperiod cues have been instrumental in expanding the geographic range of agricultural production for many crop species. Locally adaptive natural variation in photoperiod response present in wild relatives of crop plants could be leveraged to further improve the present and future climatic ranges of cu...

The growth responses of a sunflower seedling (Helianthus annuus L.), subjected to repeated inversion, were characterized by time-lapse recording in conjunction with video image analysis. The investigation revealed a characteristic response pattern and established that the directional movement of the seedling is achieved by both inhibition and stimulation of growth in the normal growing regions....

the nutrient deficiency. The apparent narrow temperature range of maximum growth found in the old cultures of Chlorella and Anacystis also seem to be caused by such secondary effects. We have therefore prepared table I from the earliest clear pattern that developed. It should represent the optimum conditions for cultivating these algae. In figure 4 the development of a Chlorella pyrenoidosa and...

Intact chloroplasts of spinach (Spinacia oleracea L.), sunflower (Helianthus annuus L.), and maize (Zea mays L.) mesophyll cells contained 0.33, 0.50, and 0.14% of bound hexosamine on a protein basis, respectively. Undifferentiated maize chloroplasts contained 0.19%. Values for chloroplast lamellae were, respectively, 0.16, 0.18, 0.12, and 0.06% and for envelope membranes they were 1.6, 2.5, 3....

Much of our knowledge of speciation genetics stems from quantitative trait locus (QTL) studies. However, interpretations of the size and distribution of QTL underlying species differences are complicated by differences in the way QTL magnitudes are estimated. Also, many studies fail to exploit information about QTL directions or to compare inter- and intraspecific QTL variation. Here, we compre...

Many studies have shown that wind affects plant development, causing them to develop shorter and usually stronger stems. Many of these effects have been shown to be due to a response to mechanical flexing of the stem which is known as thigmomorphogenesis. However, it is not known how wind affects the hydraulic properties of stems, nor have the effects of air flow past leaves been examined in is...