Robert E. Lyons

Herbarium specimens, photographs, and field observations show Philadelphia area plants are responding to climate change

PREMISE OF THE STUDY The global climate is changing rapidly and is expected to continue changing in coming decades. Studying changes in plant flowering times during a historical period of warming temperatures gives us a way to examine the impacts of climate change and allows us to predict further changes in coming decades. The Greater Philadelphia region has a long and rich history of botanical study and documentation, with abundant herbarium specimens, field observations, and botanical photographs from the mid-1800s onward. These extensive records also provide an opportunity to validate methodologies employed by other climate change researchers at a different biogeographical area and with a different group of species. METHODS Data for 2539 flowering records from 1840 to 2010 were assessed to examine changes in flowering response over time and in relation to monthly minimum temperatures of 28 Piedmont species native to the Greater Philadelphia region. KEY RESULTS Regression analysis of the date of flowering with year or with temperature showed that, on average, the Greater Philadelphia species studied are flowering 16 d earlier over the 170-yr period and 2.7 d earlier per 1°C rise in monthly minimum temperature. CONCLUSIONS Of the species studied, woody plants with short flowering duration are the best indicators of a warming climate. For monthly minimum temperatures, temperatures 1 or 2 mo prior to flowering are most significantly correlated with flowering time. Studies combining herbarium specimens, photographs, and field observations are an effective method for detecting the effects of climate change on flowering times.

Effects of GA4 + 7 on flower initiation and development and vegetative growth of Streptocarpus × hybridus Voss. ‘Hybrid Delta’

Abstract Streptocarpus × hybridus cultivar ‘Hybrid Delta’ seedlings with leaf (phyllomorph) lengths of 1, 2 or 3 cm were treated with 25 μg gibberellin (GA 4 + 7 ) per plant. One week after treatment, petiolode tissue from these plants was examined using scanning electron microscopy (SEM) for the presence of floral primordia and to track morphological changes during floral development. Samples from plants treated at 1-cm leaf lengths appeared unaffected, while those treated at the 2- and 3-cm lengths showed enhanced floral initiation and development compared with untreated controls. Gibberellin application did not affect the number of days to first flower anthesis, but did decrease the time to anthesis of second and third flowers. Peduncle length, time span between anthesis of the first three flowers and leaf length were not affected by GA 4 + 7 . Plants treated at the 3-cm lengths had more flowers per plant after 110 days compared with the remaining treatments and controls.

Controlling height of Abutilon hybrids with ancymidol, mechanical pinching and photoperiod

Abstract Vegetative and flowering characteristics of Abutilon hybridum Hort. (hybrid abutilon, flowering maple) were successfully controlled via photoperiodic, mechanical and chemical means. Short days enhanced flowering and most effectively reduced plant height and width. Hand-pinching delayed flowering, decreased flower number, leaf number and width, and reduced height only when combined with 50 p.p.m. ancymidol. When unpinched plants were treated with ancymidol, no beneficial results were obtained.