Introducing a sensor to measure budburst and its environmental drivers

Abstract

Budburst is a key adaptive trait that can help us understand how plants respond to a changing climate from the molecular to landscape scale. Despite this, acquisition of budburst data is constrained by a lack of information at the plant scale on the environmental stimuli associated with the release of bud dormancy. Additionally, to date, little effort has been devoted to phenotyping plants in natural populations due to the challenge of accounting for the effect of environmental variation. Nonetheless, natural selection operates on natural populations, and investigation of adaptive phenotypes in situ is warranted and can validate results from controlled laboratory experiments. To identify genomic effects on individual plant phenotypes in nature, environmental drivers must be concurrently measured, and characterized. Here, we designed and evaluated a sensor to meet these requirements for temperate woody plants. It was designed for use on a tree branch to measure the timing of budburst together with its key environmental drivers; temperature, and photoperiod. Specifically, we evaluated the sensor through independent corroboration with time-lapse photography and a suite of environmental sampling instruments. We also tested whether the presence of the device on a branch influenced the timing of budburst. Our results indicated the following: the temperatures measured by the budburst sensor's digital thermometer closely approximated the temperatures measured using a thermocouple touching plant tissue; the photoperiod detector measured ambient light with the same accuracy as did time lapse photography; the budburst sensor accurately detected the timing of budburst; and the sensor itself did not influence the budburst timing of Populus clones. Among other potential applications, future use of the sensor may provide plant phenotyping at the landscape level for integration with landscape genomics.

Keywords: budburst; climate change; phenology; phenotyping; photoperiod; sensing; temperature.

FIGURE 1

The bud break sensor’s fiber optic cables targeting a dormant bud, with digital thermometer below.

FIGURE 2

Schematic diagram of the bud break sensor.

FIGURE 3

Co-occurring temperatures color -coded by time of day. The black 1:1 line indicates perfect agreement between the budburst sensor digital thermometer (y-axis) and other measured temperatures (x-axis).

FIGURE 4

Average temperatures and corresponding irradiance variations for the bud break sensor’s digital thermometer (squares), air temperature (circles), thermocouple (squares), and foliar temperature (triangles).

FIGURE 5

Smoothed time series from the 11 sensor outputs showing an increased signal near the date of bud break, indicated by the vertical dotted line, using a zero-phase fifth order Butterworth filter.

FIGURE 6

Mean measurements of daylight from the bud break sensor’s photoperiod detector (in DN units) and time lapse images (in brightness values units) with 5 and 95% quantiles shaded.