the presence or absence of neighbouring plants. Now, results from the group’s experiments indicate that plants use these types of long-term prevailing light conditions as a source of information on which the acclimation of short-term responses is based. Stomata of plants growing in a shady environment are able to open faster in response to a sudden increase in the amount of light. The researchers hypothesise that even
ultraviolet radiation could be used by plants as a source of information. “Solar ultraviolet radiation is most intense on bright summer days, and so strong ultraviolet
radiation
Above: Arabidopsis mutants with altered light perception. On the left seen under visible light, and on the right in a false-colour thermal image where red indicates warmer re- gions and blue cooler ones. From the temperature of the leaves it is possible to estimate the rate of water loss.
light can be used in this way, and that it helps plants to ‘forecast’ future conditions. Plants’ physiology and growth strategy can react to these signals, enabling them to acclimate accordingly.” “Studying light as an informational signal
has become easier due to three recent developments,” continues Aphalo. “Firstly, high-power LEDs have been engineered which can provide very pure, specific colours of light which can be used to create the experimental conditions needed to test plant responses. Secondly, mutant plants lacking the ability to respond to certain signals are readily available. Thirdly, sensitive modern equipment means that our assessments of plant responses can be more accurate.
Measuring photosynthesis,
respiration and transpiration by small plants, and even from individual leaves, has been possible for many years, but portability of
the equipment has
meteorology, ecology and molecular biology – are involved in our work,” says Aphalo. “This is important, as we need to appreciate how plants react to a number of different phenomena at different scales.” To realise this multi-disciplinary approach, academics from the University
could hint at an impending drought,” says Aphalo. “We contend that plants adjust their growth and physiology to prepare for these harsher conditions and drier soil. To validate this, we’re working with the Finnish Meteorological Institute to assess how reliable a forewarning this type of radiation could provide.”
Responses,
Aphalo notes, vary significantly between species, but the scientist has been surprised by the consistency of “degree of fine control” exercised by his subjects. Although wary of the potentially misleading connotations of terms like “plant intelligence”, he’s convinced that by reacting to challenges perceived through informational signals in the environment, these and other organisms can adapt to
“Analysing several species (both trees, and
forbs, including vegetables, ornamentals and field crops) has already yielded a number of fascinating insights”
improved. Light
measuring instrumentation has also improved in portability and speed of measurement.” A significant challenge for research in this area is that controlled environment plant-growth facilities often fail to comprehensively emulate all of the conditions plants would encounter in the open air. To overcome this, Aphalo’s team has been combining outdoor experiments that use light-absorbing filters with indoor trials that exploit LEDs. “Specialists from several fields – including climatology, micro-
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of Buenos Aires in Argentina, the University of Glasgow in Scotland, Örebro University in Sweden and Ben-Gurion University of the Negev in Israel are some of the experts contributing to the research by the team in Helsinki. Analysing several species (both trees, and
forbs, including vegetables, ornamentals and field crops) has already yielded a number of fascinating insights. Plants readily perceive and utilise regions of the solar spectrum that our eyes can barely see, such as far-red (located in-between the red and infrared bands) and ultraviolet. It is well known that the red to far-red photon ratio provides information to plants about
survive and efficiently reproduce in a constantly changing environment – attributes which could be manipulated to enable them to contribute to human welfare. “These mechanisms serve an important
function by enhancing the organisms’ Darwinian fitness – the ultimate cause for their existence – and have evolved over lengthy timescales,” says Aphalo. “But, plants achieve fitness by responding to light in several more immediate ways i.e. the proximate causes or mechanisms. For instance, the amount and composition of flavonoids – pigments known for their anti- oxidant properties – change according to light quality. By manipulating this variable,
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