Atmospheric moisture controls far-red irradiation: a probable impact on the phytochrome

Abstract

A b s t r a c t. It is commonly accepted that an important role of the phytochrome lies in signalling the proximity of competing plants. However, not all photoresponses conveyed by the phytochrome can be explained by the competition only. Because a better description of the natural variability of solar spectral irradiance is necessary to recognize the other roles of the phytochrome, long-lasting spectroradiometric measurements have been performed. Special attention has been paid to the relations between the far-red and red bands of the solar spectrum, which have an impact on the phytochrome. The effect of atmospheric moisture on far-red irradiance (attenuated in the 720 nm band of water vapour absorption) is described. The far-red irradiance, active in the 'high irradiance response' of the phytochrome, and the red/ far-red ratio, important for the 'low fluence response', may vary very strongly relative to the atmospheric moisture. Together with other facts known from photophysiology, the results of the measurements enabled us to formulate a thesis that the phytochrome monitors the amount of water vapour and opens appropriate metabolic pathways to cope with the danger of drought. The recognition of this novel role of the phytochrome might broaden the knowledge in the area of plant photomorphogenesis and ecology.

Environmental Drivers of Gross Primary Productivity and Light Use Efficiency of a Temperate Spruce Forest

“…Data from the six R/FR sensors were averaged for the calculation of R/FR trans . As R/FR is strongly dependent on solar elevation and the precipitable water vapor in the atmosphere, which attenuates light in the far-red but not in the red domain (Doroszewski et al, 2015;Kotilainen et al, 2020), we also calculated the difference between the R/FR ratios above and below the canopy as 𝐴𝐴 𝐴𝐴∕FRdiff = 𝐴𝐴in∕FRin − 𝐴𝐴trans∕FRtrans to represent the change of the spectral ratio caused by the canopy alone. All radiation data were filtered for daytime conditions (PAR in > 10 μmol m −2 s −1 ) and linked to GPP estimates by aggregating them to 30-min values.…”

Far Red and Red as Factors Forming Physiological Processes in Spring Barley under Controlled Conditions

“…The response of wheat plants was similar, although less spectacular [36]. On this basis, it can be assumed that these responses are undoubtedly a manifestation of adaptation of plants growing under radiation conditions with a low R/FR ratio to restrict water consumption with regards to expected competition or droughts because a lower R/FR ratio occurs in a dry atmosphere and a higher one occurs in an atmosphere with a lot of moisture [11]. Similar results were obtained in relation to the transpiration of cotton and Abutilon theophrasti plants, which also showed a lower use of water at a low R/FR ratio than under radiation with a higher value of this ratio [39,40].…”

“…From the spectral-radiometric measurements performed in the outdoor positions [11], it appears that the R/FR ratio in the solar radiation is close to 1, while in the dense cereal stands it can be lower than 0.07 [36]. The R/FR ratio has a significant effect on photochromic reactions, which have a considerable effect on the development and yielding of plants.…”

“…Shade avoidance syndrome (SAS) [2,4,5] is frequently caused by FR reflected from neighboring plants, even before the growth of the stand, which means that plants can detect and react to potential future competition just before the shading [1,[6][7][8]. Natural shading in stands give a low R/FR ratio [9,10] when compared to natural solar radiation in an open space [11,12] because a high absorption of chlorophyll and other photosynthetic pigments in the range of the blue and red spectrum causes the absorption of radiation in this range to be high, while in the range above 700 nm it is relatively low.…”

Analysis of moisture conditions in the lowland areas using high resolution spectral data from the Sentinel-2 satellite and the GIS tools

“…Drought is the most complicated climatic phenomenon among the hazards related to weather [9,15]. Agricultural drought research are focuses on the use of methods based on the long-term atmospheric data, temperature, precipitation or evaporation measurements; without taking into account changes in the soil properties and parameters [18,25].…”