Paper of the week
Summary - This paper aim to assess differences in the seasonal regulation of photosynthesis and the associated variation of carotenoids and chlorophylls at the leaf-scale for eastern white pine, red maple and white oak, in order to understand if photosynthetic and photoprotective processes are adequately represented by different vegetation indices over the course of the year.
What is important - This study shows that carotenoid sensitive vegetation indices, such as PRI and CCI, are an alternative approach that exploits the seasonal variation in carotenoid content that contributes to the regulation of photosynthesis over the course of the season and in response to environmental stress in both deciduous and evergreen trees .
My thought - Work at larger spatial scales is needed to explore canopy-scale PRI and CCI which may offer a powerful means to monitor photosynthesis and phenology across deciduous and evergreen vegetation types via remote sensing.
Summary - This paper that explains some concepts of chlorophyll fluorescence is written for novice. In particular, it explains easily to those who study the concepts of ‘light double’ technique for calculating PQ and NPQ using some equations. Subsequently, limitations and alternatives are presented.
What is important – Photochemical quenching parameters always relate to the relative value of maximum fluorescence and steady-state yield of fluorescence in the light. And if we know some value of fluorescence, we can calculate most photochemical quenching parameters and non-photochemical quenching parameters.
My thought – This paper was very helpful to me as a beginner. I know this paper omits the detailed concept for beginners, but I think I need to know more deeply to master this field. So I am going to read reference in this paper and study them in more detail.
Thenot, F., Méthy, M., & Winkel, T. (2002). The Photochemical Reflectance Index (PRI) as a water-stress index. International Journal of Remote Sensing, 23(23), 5135-5139.
Summary – This paper deals with the use of PRI as a water-stress index. Contrasted structural and functional types of plants will be considered. But this paper suggested that the use of PRI for water stress is possible only for moderate stress intensity.
My thought – Actually, I can’t get important point in this paper. This paper is so peripheral that it is difficult to apply to other fields. I also felt that the design of the experiment was not perfect. I could feel why Professor ryu told us to choose a paper from a good journal.
Peñuelas, J., Filella, I., & Gamon, J. A. (1995). Assessment of photosynthetic radiation‐use efficiency with spectral reflectance. New Phytologist, 131(3), 291-296.
Summary – This paper suggested that 531nm reflectance(which PRI is based) could provide a widely applicable index of photosynthetic function compared to photosynthetic radiation-use efficiency(PRUE) and quantum yield of PSⅡ.
What is important – Reflectance change at 531 nm has two components, one near 525 nm, associated with the interconversion of the xanthophyll cycle pigments, and one near 539 nm, associated with reversible chloroplast conformational changes linked to the trans-thylakoid pH gradient. This reflectance change at 531 nm has two components, one near 525 nm, associated with the interconversion of the xanthophyll cycle pigments, and one near 539 nm, associated with reversible chloroplast conformational changes linked to the trans-thylakoid pH gradient. Many plant species of widely varying habit, phenology, leaf anatomy, and photosynthetic pathway, all exhibited reflectance changes upon increased illumination and centred at or near 531 nm.
My thought – This paper said “Application of validation of 531nm-based index at spatial scales larger than the leaf requires careful attention to confounding effects of canopy structure on this relatively small reflectance signal.” But I don’t know what we have to pay attention to. So, I should study this by reading various papers.
1st Sep, 2020.
Monteith, J. L. (1972). Solar radiation and productivity in tropical ecosystems. Journal of applied ecology, 9(3), 747-766.
Summary – This paper suggests the model of the efficiency which plants store solar energy using Seven parameter and gets two generalization point that primary production and secondary production by analysis data of data got test at three tropical resions.
What is important I think – The efficiency with which plants store solar energy in this model can be expressed as the product of seven factors which describe the dependence of dry matter production on latitude and season, on cloudiness and the aerosol content of the atmosphere, on the spectral composition of radiation and the quantum need of the photochemical process, on leaf area index and leaf arrangement, on the concentration of CO2 in the canopy and the diffusion resistance of individual leaves, and on the fraction of assimilates used in respiration.
My though – 1) This paper approaches the ecosystem from thermodynamic perspective. That is why this model is interested in energy conversion efficiency. It is gives me a concepts for overall GPP and NPP. 2) Unlike when this paper was written, GPP = PAR×FPAR×LUE, NPP = GPP - respiration [by plants] are common model nowadays. Compared to that time, the current remote sensing field has made a lot of progress and is overcoming various limitations which this model ignores. So I become curious about how the model has changed over time with the concept which presented seven parameters in the paper.