SPAD chlorophyll meter reading can be pronouncedly affected by chloroplast movement

Abstract

Non-destructive assessment of chlorophyll content has recently been widely done by chlorophyll meters based on measurement of leaf transmittance (e.g. the SPAD-502 chlorophyll meter measures the leaf transmittance at 650 and 940 nm). However, the leaf transmittance depends not only on the content of chlorophylls but also on their distribution in leaves. The chlorophyll distribution within leaves is co-determined by chloroplast arrangement in cells that depends on light conditions. When tobacco leaves were exposed to a strong blue light (about 340 μmol of photons m⁻² s⁻¹), a very pronounced increase in the leaf transmittance was observed as chloroplasts migrated from face position (along cell walls perpendicular to the incident light) to side position (along cell walls parallel to the incoming light) and the SPAD reading decreased markedly. This effect was more pronounced in the leaves of young tobacco plants compared with old ones; the difference between SPAD values in face and side position reached even about 35%. It is shown how the chloroplast movement changes a relationship between the SPAD readings and real chlorophyll content. For an elimination of the chloroplast movement effect, it can be recommended to measure the SPAD values in leaves with a defined chloroplasts arrangement.

Use of a SPAD-502 meter to measure leaf chlorophyll concentration in Arabidopsis thaliana

“…It should be noted that SPAD meter readings can be influenced by changing growth conditions that, for example, may lead to a redistribution of chloroplasts within mesophyll cells (Naus et al 2010). For this reason, it is advisable to always include an internal control in each experiment, as a point of reference, and to be cautious about making comparisons between experiments conducted on different occasions.…”

Modelling of the relationship between the SPAD values and photosynthetic pigments content in Quercus petraea and Prunus serotina leaves

“…They may be caused by species-specific leaf structure, adaptation to the local light environments, nutrients availability and other abiotic and biotic factors which may modify leaf optical properties. Additionally, the SPAD readings can be significantly affected by the sieve effect and optical path lengthening caused by high heterogeneity in Chl distribution within a leaf (Uddling et al 2007;Marenco et al 2009;Nauš et al 2010). In our study species, the differences in the relationship between the SPAD readings and real Chl content cannot rather be attributed to the chloroplast movement because the measurements were conducted at the same time on each occasion.…”

“…To reduce the impact of daily chloroplasts movement on SPAD values, the measurements in each individual sampling time were conducted at the same day time from 9:00 to 12:00 (Nauš et al 2010). The meter head was placed at adaxial leaf surface avoiding a mid-vein.…”

Relationship between leaf physiologic traits and canopy color indices during the leaf expansion period in an oak forest

“…The SPAD values are calculated through the amount of light transmitted by the leaf in red light (650 nm) and infrared light (940 nm), which have different absorbance induced by chlorophyll. Although the relationship between SPAD values and chlorophyll contents could be linear, exponential or polynomial correlations for various kinds of plants species have been reported; this relationship could be affected by light conditions, chloroplast distribution or the level of chlorophyll concentrations, but overall, the dynamic curve of SPAD values could be used as the indicator of leaf chlorophyll contents (Markwell et al 1995, v www.esajournals.org Muraoka and Koizumi 2005, Uddling et al 2007, Naus et al 2010, Ling et al 2011, Nagai et al 2011, Djumaeva et al 2012, Scattolin et al 2013, Riccardi et al 2014. Furthermore, the daily leaf area index (LAI) values (lower frequency after the end of leaf expansion) within ROI were collected with the leaf area meter LAI-2200 (Li-COR, Nebraska, USA) at the same time with other measurements.…”