Growth and photosynthetic characteristics of progeny from winter and summer-active Helianthus in the Corpus Christi, TX area

Background/Question/Methods

Helianthus annuus is the most common species of sunflower in North America and is commonly found growing and flowering year-round in Corpus Christi, Texas.  To determine if there are differences in growth and photosynthetic characteristics between progeny from summer-active and winter-active plants during each season, plants were grown individually and with 2 or 4 associates from the opposite group of plants during the winter and summer growing seasons.  Our hypothesis is that there is no difference in growth and photosynthetic characteristics between progeny from winter-active and summer-active plants during either season.  If so, as climate changes, this could lead to the establishment of winter-active cohorts in more northern areas. 

Results/Conclusions

We found no significant difference in photosynthetic rate measured in February 2013 for target plants between progeny from winter-active and summer-active plants (P=0.0810).  In addition, there was no difference in height for target plants (P=0.3709) or for height of associate plants (P=0.448).  In the winter growing season, progeny from summer-active plants are doing as well as are progeny from winter-active plants.  We found no differences in growth and photosynthetic characteristics between progeny from summer-active and winter-active plants indicating that H. annuus could extend its growing season in regions farther north of our area if winters become warmer in these areas.