Sensory and Physiological Ecology of Plants

The opinions in this post are those of the author (Pedro J. Aphalo).

The scientific discussion about “plant intelligence” was started by Anthony Trewavas nearly 20 years ago, culminating with the publication of his book Plant Behaviour and Intelligence. The use of the word “intelligence” for plants was then controversial and remains nowadays still controversial. On the other hand the phenomena described and the experiments used as support used by Trewavas are not specially controversial.

In recent times the use of the term “plant intelligence” has reached the daily press and science popularization books in addition to videos in the internet. Much of this recent material is not only controversial in the meaning given to the word “intelligence” but also in the quality or strength of the evidence presented. This has led, in my view, to confusion and misinterpretations of what has been actually demonstrated with experiments versus what remians as tentative hypotheses in need of (further) testing. Continue reading “What is plant intelligence? and what it is not?”

Our Update article has been published in July’s issue of Plant Physiology. It summarizes the current state of knowledge including the new understanding and insights brought to light by the research by our group in Helsinki, done with the help of several collaborators.

Title: Perception of solar UV radiation by plants: photoreceptors and mechanisms

Authors: Neha Rai, Luis O. Morales, Pedro J. Aphalo

Neha Rai is now at the University of Geneva in Roman Ulm’s lab.

Luis O. Morales is at Örebro University leading his own research group.

DOI (open access): https://doi.org/10.1093/plphys/kiab162

Abstract:

About 95% of the ultraviolet (UV) photons reaching the Earth’s surface are UV-A (315–400 nm) photons. Plant responses to UV-A radiation have been less frequently studied than those to UV-B (280–315 nm) radiation. Most previous studies on UV-A radiation have used an unrealistic balance between UV-A, UV-B, and photosynthetically active radiation (PAR). Consequently, results from these studies are difficult to interpret from an ecological perspective, leaving an important gap in our understanding of the perception of solar UV radiation by plants. Previously, it was assumed UV-A/blue photoreceptors, cryptochromes and phototropins mediated photomorphogenic responses to UV-A radiation and “UV-B photoreceptor” UV RESISTANCE LOCUS 8 (UVR8) to UV-B radiation. However, our understanding of how UV-A radiation is perceived by plants has recently improved. Experiments using a realistic balance between UV-B, UV-A, and PAR have demonstrated that UVR8 can play a major role in the perception of both UV-B and short-wavelength UV-A (UV-A_sw, 315 to ∼350 nm) radiation. These experiments also showed that UVR8 and cryptochromes jointly regulate gene expression through interactions that alter the relative sensitivity to UV-B, UV-A, and blue wavelengths. Negative feedback loops on the action of these photoreceptors can arise from gene expression, signaling crosstalk, and absorption of UV photons by phenolic metabolites. These interactions explain why exposure to blue light modulates photomorphogenic responses to UV-B and UV-A_sw radiation. Future studies will need to distinguish between short and long wavelengths of UV-A radiation and to consider UVR8’s role as a UV-B/UV-A_sw photoreceptor in sunlight.

Figure 5 from the paper at Plant Physiology web site

We have a weather station at our experimental field that I look after. It started collecting data in 2015 and in 2020 it had a large upgrade. There is a full description of the equipment and measurements at https://viikki-stn.r4photobiology.info/.

Differently to standard meteorological stations data are logged for most variables at 1 min intervals, as means of 12 measurements taken at 5 s intervals. Hourly and daily summaries are also stored.

Currently the station logs more than 40 variables, a few of them from multiple sensors. Special emphasis is on solar radiation, with measurements of photon irradiance for UV-B, UV-A, blue, red and far-red, and global energy irradiance. Differently to measurements of  erythemal, i.e., biologically effective UV radiation more commonly available, UV-A and UV-B irradiances are measured separately and without applying a spectral weighting function.

With the most recent upgrade we started measurements of the profile of soil temperature, water content and electrical conductivity. Surface temperature is measured on vegetation and/or bare soil with non-contact (infrared) sensors.

The usual air temperature, water vapour pressure, atmospheric pressure, wind speed, wind direction and rainfall are also recorded. The data are available on request. The radiation data for the winter period are less reliable than for the growth season, and there are also some gaps in past winters for all variables.