Relationships between the photochemical reflectance index (PRI) and chlorophyll fluorescence parameters and plant pigment indices at different leaf growth stages

This study aimed to evaluate the photochemical reflectance index (PRI) for assessing plant photosynthetic performance throughout the plant life cycle. The relationships between PRI, chlorophyll fluorescence parameters, and leaf pigment indices in Solanum melongena L. (aubergine; eggplant) were studied using photosynthetic induction curves both in short-term (diurnal) and long-term (seasonal) periods under different light intensities. We found good correlations between PRI/non-photochemical quenching (NPQ) and PRI/electron transport rate (ETR) in the short term at the same site of a single leaf but these relationships did not hold throughout the life of the plant. In general, changes in PRI owing to NPQ or ETR variations in the short term were <20?% of those that occurred with leaf aging. Results also showed that PRI was highly correlated to plant pigments, especially chlorophyll indices measured by spectral reflectance. Moreover, relationships of steady-state PRI/ETR and steady-state PRI/photochemical yield of photosystem II (Φ(PSII)) measured at uniform light intensity at different life stages proved that overall photosynthesis capacity and steady-state PRI were better correlated through chlorophyll content than NPQ and xanthophylls. The calibrated PRI index accommodated these pigments effects and gave better correlation with NPQ and ETR than PRI. Further studies of PRI indices based on pigments other than xanthophylls, and studies on PRI mechanisms in different species are recommended.     

Surface reflectance properties of Antarctic moss and their relationship to plant species, pigment composition and photosynthetic function

In this study the variations in surface reflectance properties and pigment concentrations of Antarctic moss over species, sites, microtopography and with water content were investigated. It was found that species had significantly different surface reflectance properties, particularly in the region of the red edge (approximately 700 nm), but this did not correlate strongly with pigment concentrations. Surface reflectance of moss also varied in the visible region and in the characteristics of the red edge over different sites. Reflectance parameters, such as the photochemical reflectance index (PRI) and cold hard band were useful discriminators of site, microtopographic position and water content. The PRI was correlated both with the concentrations of active xanthophyll‐cycle pigments and the photosynthetic light use efficiency, F_v/F_m, measured using chlorophyll fluorescence. Water content of moss strongly influenced the amplitude and position of the red‐edge as well as the PRI, and may be responsible for observed differences in reflectance properties for different species and sites. All moss showed sustained high levels of photoprotective xanthophyll pigments, especially at exposed sites, indicating moss is experiencing continual high levels of photochemical stress.     

Photochemical reflectance index as a mean of monitoring early water stress

Water stress in plants affects a number of physiological processes such as photosynthetic rate, stomatal conductance as well as the operating efficiency of photosystem II (PSII) and non-photochemical quenching (NPQ). Photochemical reflectance index (PRI) is reported to be sensitive to changes in xanthophyll cycle which occur during stress and could possibly be used to monitor changes in the parameters mentioned before. Therefore, the aim of this study was to evaluate the use of PRI as an early water stress indicator. Water stress treatment was imposed in a greenhouse tomato crop. CO₂ assimilation, stomatal conductance, light-adapted and dark-adapted fluorescence as well as PRI and relative water content (RWC_s%) of the rooting medium were repeatedly measured. The same measurements were also performed on well-irrigated plants that acted as a reference. The experiment was repeated in four consecutive weeks. Results showed a strong correlation between RWC_s% and photosynthetic rate, stomatal conductance, NPQ and operating efficiency of PSII but not with PRI when the whole dataset was considered. Nevertheless, more detailed analysis revealed that PRI gave a good correlation when light levels were above 700 µmol m⁻² s⁻¹. Therefore, the use of PRI as a water stress indicator cannot be independent of the ambient light conditions.     

Responses of CO2, CH4 and N2O fluxes to livestock exclosure in an alpine steppe on the Tibetan Plateau, China

Background and aims

The photochemical reflectance index (PRI) is correlated to photosynthetic efficiency and has been successfully applied at multiple scales for remote estimation of physiological functioning. However, interpretation of the PRI signal can be confounded by many different variables including declines in photochemical pigments. Our study was aimed at investigating PRI in response to salinity stress, and evaluating physiological and pigment responses of two co-occurring shrubs, Baccharis halimifolia and Myrica cerifera in laboratory studies.

Methods

Photosynthesis, water relations, chlorophyll fluorescence, hyperspectral reflectance and leaf pigment contents were measured following salinity treatment.

Results

Physiological measurements indicated that both species exhibit adaptations which protect PSII during periods of stress. Chlorophyll fluorescence parameters were affected in both species, but indicated that other photochemical reactions (e.g. photorespiration) were important for energy dissipation in absence of chlorophyll changes. After many days of reduced photosynthesis, photochemical changes were detectable using PRI indicating chronic stress.

Conclusions

Variations in PRI were not related to changes in pigments but strongly related to tissue chlorides indicating salinity effects on the PRI signal. Thus, PRI is an indicator of salinity stress in these coastal species and may be as an early signal for increasing salt exposure associated with rising sea-level and climate change.     

Gas exchange,chlorophyll fluorescence,and osmotic adjustment in two mango cultivars under drought stress

The responses of photosynthetic gas exchange, chlorophyll fluorescence, content of pigments, main osmolytes, and malondialdehyde (MDA) to water-withholding for 15 days and re-hydration in seedlings of two mango cultivars (Mangifera indica L. var. “Choke Anand’ and var. “Khieo Sawoei”) under 50% sunlight and full sunlight were investigated. For both cultivars, the water-witholding resulted in progressively decreases in leaf relative water content, net photosynthesis (P _n), stomatal conductance (g _s), and increases in the conversion of xanthophyll cycle pigments estimated by an index of leaf spectral reflectance (ΔPRI), carotenoid to chlorophyll ratio, non-photochemical quenching (NPQ), the contents of malondialdehyde (MDA) and compatible solutes (total soluble sugar and proline). The effect of the water stress was more pronounced in full sunlight than 50% sunlight. The maximum photochemistry efficiency measured at dawn was fairly constant during the period of the treatment for both cultivars under both light regimes. The water stress caused less pronounced inhibition of photosynthesis in “Choke Anand” than in “Khieo Sawoei” cultivar under both light regimes. After re-hydration, the recovery was relatively quicker in “Choke Anand” than in “Khieo Sawoei” cultivar. Both cultivars in both 50% and full sunlight showed complete recovery in photochemistry after 5 days of re-watering but photosynthesis did not show a complete recovery as indicated by gas exchange rates. As the results of lower NPQ, ΔPRI and osmotic adjustment in the cultivar “Khieo Sawoei” compared to the cultivar “Choke Anand”, the former cultivar was less tolerant to drought than the latter. Our study further showed that partial shading (e.g., 50% of sunlight) significantly alleviated the harmful effect of drought stress on mango cultivars but in fact stomata of seedlings grown in partial shade was more responsive to water deficit than in full light.     

Assessing photosynthetic efficiency in an experimental mangrove canopy using remote sensing and chlorophyll fluorescence

This study examined the ability of the photochemical reflectance index (PRI) to track changes in effective quantum yield (Δ F/F _m ′), non-photochemical quenching (NPQ), and the xanthophyll cycle de-epoxidation (DPS) in an experimental mangrove canopy. PRI was correlated with (Δ F/F _m ′) and NPQ over the 4-week measurement period and over the diurnal cycle. The normalised difference vegetation index (NDVI) was not correlated with any aspect of photochemical efficiency measured using chlorophyll fluorescence or xanthophyll pigments. This study demonstrated that photochemical adjustments were responsible for controlling the flow of energy through the photosynthetic apparatus in this mangrove forest canopy rather than canopy structural or chlorophyll adjustments.     

Inhibition of photosynthesis in olive trees (Olea europaea L.) during water stress and rewatering

The effect of high levels of natural light on leaf photosynthesisin olive trees (Olea europaea L. var. Coratina), grown in potsoutdoors in the summer and subjected to water, stress, was studied.Net photosynthetic rates reached maximum values early in themorning in both control and stressed plants and subsequentlydeclined gradually. This inactivation of photosynthetic activitywas accompanied by changes in the fluorescence characteristicsof the upper intact leaf surface. The maximum fluorescence yield(Fp) and the ratio Fv/Fp decreased at midday especially in water-stressedplants, but the initial fluorescence (Fo) rose to a maximumvalue at midday and declined again in the afternoon. In controlplants the values of maximum fluorescence Fp and the ratio Fv/Fpincreased again in the afternoon and had recovered almost completelyby 8 p.m. as the leaf water potential recovered. In stressedplants this diurnal recovery was not complete, so that the photosyntheticrates and the ratio Fv/Fp declined gradually during the developmentof water stress. These results indicate that in olive treessubjected to severe water stress the non-stomatal componentof photosynthesis was affected and perhaps a light-dependentinactivation of the primary photochemistry associated with photosystemII (PSII) occurred. Four to five days after rewatering severelystressed plants, the predawn leaf water potential, net photosyntheticrates and chlorophyll fluorescence indices recovered only partially. Key words: Olea europaea, photosynthesis, water stress, chlorophyll a fluorescence, inhibition of photosynthesis     

Spectral reflectance indices and pigment functions during leaf ontogenesis in six subtropical landscape plants

Pigment combinations are regulated during leaf ontogenesis. To better understand pigment function, alterations in chlorophyll, carotenoid and anthocyanin concentrations were investigated during different leaf development stages in six subtropical landscape plants, namely Ixora chinensis Lam, Camellia japonica Linn, Eugenia oleina Wight, Mangifera indica L., Osmanthus fragrans Lowr and Saraca dives Pierre. High concentrations of anthocyanin were associated with reduced chlorophyll in juvenile leaves. As leaves developed, the photosynthetic pigments (chlorophyll and carotenoid) of all six species increased while anthocyanin concentration declined. Chlorophyll fluorescence imaging of Φ_PSII (effective quantum yield of PSII) and of NPQ (non-photochemical fluorescence quenching) and determination of electron transport rate-rapid light curve (RLC) showed that maximum ETR (leaf electron transport rate), Φ_PSII and the saturation point in RLC increased during leaf development but declined as they aged. Juvenile leaves displayed higher values of NPQ and Car/Chl ratios than leaves at other developmental stages. Leaf reflectance spectra (400–800 nm) were measured to provide an in vivo non-destructive assessment of pigments in leaves during ontogenesis. Four reflectance indices, related to pigment characters, were compared with data obtained quantitatively from biochemical analysis. The results showed that the ARI (anthocyanin reflectance index) was linearly correlated to anthocyanin concentration in juvenile leaves, while a positive correlation of Chl NDI (chlorophyll normalized difference vegetation index) to chlorophyll a concentration was species dependent. Photosynthetic reflectance index was not closely related to Car/Chl ratio, while a structural-independent pigment index was not greatly altered by leaf development or species. Accordingly, it is suggested that the high concentration of anthocyanin, higher NPQ and Car/Chl ratio in juvenile leaves are important functional responses to cope with high radiation when the photosynthetic apparatus is not fully developed. Another two leaf reflectance indices, ARI and Chl NDI, are valuable for in vivo pigment evaluation during leaf development.     

Action potential in a plant cell lowers the light requirement for non-photochemical energy-dependent quenching of chlorophyll fluorescence

This study deals with effects of membrane excitation on photosynthesis and cell protection against excessive light, manifested in non-photochemical quenching (NPQ). In Chara corallina cells, NPQ and pericellular pH displayed coordinated spatial patterns along the length of the cell. The NPQ values were lower in H(+)-extruding cell regions (external pH approximately 6.5) than in high pH regions (pH approximately 9.5). Generation of an action potential by applying a pulse of electric current caused NPQ to increase within 30-60 s. This effect, manifested as a long-lived drop of maximum chlorophyll fluorescence (F(m)'), occurred at lower photosynthetic flux densities (PFD) in the alkaline as compared to acidic cell regions. The light response curve of NPQ shifted, after generation of an action potential, towards lower PFD. The release of NPQ by nigericin and the rapid reversal of action potential-triggered NPQ in darkness indicate its relation to thylakoid DeltapH. Generation of an action potential shortly after darkening converted the chloroplasts into a latent state with the F(m) identical to that of unexcited cells. This state transformed to the quenched state after turning on weak light that was insufficient for NPQ prior to membrane excitation of the cells. The ionophore, A23187, shifted NPQ plots similarly to the action potential effect, consistent with a likely role of a rise in the cytosolic Ca(2+) level in the action potential-induced quenching. The results suggest that a rapid electric signal, across the plasma membrane, might exert long-lived effects on photosynthesis and chlorophyll fluorescence through ion flux-mediated pathways.     

Physiology of the seasonal relationship between the photochemical reflectance index and photosynthetic light use efficiency

The photochemical reflectance index (PRI) is regarded as a promising proxy to track the dynamics of photosynthetic light use efficiency (LUE) via remote sensing. The implementation of this approach requires the relationship between PRI and LUE to scale not only in space but also in time. The short-term relationship between PRI and LUE is well known and is based on the regulative process of non-photochemical quenching (NPQ), but at the seasonal timescale the mechanisms behind the relationship remain unclear. We examined to what extent sustained forms of NPQ, photoinhibition of reaction centres, seasonal changes in leaf pigment concentrations, or adjustments in the capacity of alternative energy sinks affect the seasonal relationship between PRI and LUE during the year in needles of boreal Scots pine. PRI and NPQ were highly correlated during most of the year but decoupled in early spring when the foliage was deeply downregulated. This phenomenon was attributed to differences in the physiological mechanisms controlling the seasonal dynamics of PRI and NPQ. Seasonal adjustments in the pool size of the xanthophyll cycle pigments, on a chlorophyll basis, controlled the dynamics of PRI, whereas the xanthophyll de-epoxidation status and other xanthophyll-independent mechanisms controlled the dynamics of NPQ at the seasonal timescale. We conclude that the PRI leads to an underestimation of NPQ, and consequently overestimation of LUE, under conditions of severe stress in overwintering Scots pine, and most likely also in species experiencing severe drought. This severe stress-induced decoupling may challenge the implementation of the PRI approach.     

Diurnal variation in photochemical dynamics and surface reflectance of the desiccation-tolerant moss,Tortula ruralis

Most desiccation-tolerant plants alter shoot structure during drying, making it possible to use changes in surface reflectance as a proxy measure of plant water status. Diurnal courses of surface reflectance (albedo) and chlorophyll fluorescence parameters of the ectohydric moss, Tortula ruralis (Hedw.) Gaertn, were measured to assess the coordination between anatomical and physiological features under field conditions. Albedo showed a sigmoidal relationship with relative humidity and the deviation of moss mat temperature from dew point. Maximum photosynthetic quantum yield (F _v/F _m) also displayed a sigmoidal relationship pooled across three days differing in light, temperature, and relative humidity. Depending on the light conditions and rapidity of drying during the morning, there were distinct differences in the ability of T. ruralis to establish thermal dissipation of excess light energy (NPQ) across a range of light levels following rehydration through the day. These findings suggest that there is a coordinated suite of architectural and physiological characteristics maintaining the photosynthetic integrity of these plants in highly variable arid and semi-arid environments.     

Nondestructive evaluation of the photosynthetic properties of micropropagated plantlets by imaging photochemical reflectance index under low light intensity

The photochemical reflectance index (PRI) of micropropagated potato leaves was estimated nondestructively from outside the culture vessel using a PRI imaging system developed by the present group. The PRI was determined under low light intensity conditions after dark treatment and compared with the chlorophyll fluorescence parameter Fv/Fm, which denotes photosystem II maximum quantum yield. Short-term high-light treatment decreased Fv/Fm of the plantlets. Culture conditions such as temperature and sucrose concentration also affected Fv/Fm. A linear relationship between the PRI and Fv/Fm was observed in both cases of high-light treatment and different culture conditions, suggesting the potential of the PRI to be used as a substitute for Fv/Fm. PRI estimated from reflection images under low light intensity conditions may be used for rapid and noninvasive evaluation of photosynthetic properties of micropropagated plantlets in a similar manner to Fv/Fm.     

Diurnal patterns of photosynthesis, chlorophyll fluorescence, and PRI to evaluate water stress in the invasive species, Elaeagnus umbellata Thunb.

Photosynthesis, chlorophyll fluorescence, and hyperspectral reflectance were used to evaluate diurnal changes of Elaeagnus umbellata to quantify physiological responses of the invasive species during times of stress. Field measurements showed that E. umbellata is able to maintain higher levels of photosynthesis relative to nearby Quercus alba plants, with less water loss. Plants subjected to progressive drought were able to recover photosynthesis one day following re-watering. Laboratory and field measurements revealed decreasing ΔF/F′_m values in response to drought stress, with little corresponding decrease in photochemical reflectance index values. This research supports the view that xanthophyll cycle dissipation is not the photoprotective mechanism at work for Elaeagnus species under water stress. Elaeagnus umbellata maintains photosynthetic carbon assimilation even under drought conditions, in part, due to chemical dissipation of excess light, and in part because of morphological features that limit excess radiation while maximizing photosynthetic carbon gain. These characteristics may contribute to the invasive success of E. umbellata.     

Analysis of Photosynthetic Activity at the Leaf and Canopy Levels from Reflectance Measurements: A Case Study

The photochemical reflectance index (PRI), based on reflectance signatures at 531 and 570 nm, and associated with xanthophyll pigment inter-conversion and related thylakoid energisation, was evaluated as an indicator of photosynthetic function in a Mediterranean holm oak (Quercus ilex L.) coppice. The chlorophyll fluorescence pulse-amplitude-modulation and the eddy correlation techniques were used to estimate the photosystem 2 photochemical efficiency of leaves and the CO₂ flux over the canopy, respectively. The reflectance and fluorescence techniques yielded identical estimates of the photosynthetic activity in leaves exposed to dark-light-dark cycles or to a variable irradiance in laboratory. However, there was no such correlation between photosynthetic performance and PRI when applied to a sun-exposed canopy in field conditions. Fluorescence profiles inside the canopy and especially a helpful use of multispectral reflectance imaging highlight the limitations of such method.     

Operation of the xanthophyll cycle and degradation of D1 protein in the inducible CAM plant,Talinum triangulare,under water deficit

Changes in photochemical activity induced by water deficit were investigated in Talinum triangulare, an inducible CAM plant. The aim was to analyse the interactions between C3 photosynthesis, induction and activity of CAM, photosynthetic energy regulation and the mechanisms responsible for photoprotection and photoinhibition under water stress. Gas exchange, chlorophyll a fluorescence, titratable acidity, carotenoid composition and relative contents of the PSII reaction centre protein (D1) were measured. A decrease in xylem tension (psi) from -0.14 to -0.2 MPa substantially decreased daytime net CO2 assimilation and daily carbon gain, and induced CAM, as shown by CO2 assimilation during the night and changes in titratable acidity; a further decrease in psi decreased nocturnal acid accumulation by 60%. Non-photochemical quenching of chlorophyll a fluorescence (NPQ) increased with water deficit, but decreased with a more severe drought (psi below -0.2 MPa), when CAM activity was low. NPQ was lower at 0900 h (during maximum decarboxylation rates) than at 1400 h, when malate pools were depleted. Down-regulation of PSII activity related to the rise in NPQ was indicated by a smaller quantum yield of PSII photochemistry (phiPSII) in droughted compared with watered plants. However, phiPSII was larger at 0900 h than at 1400 h. The de-epoxidation state of the xanthophyll cycle increased with drought and was linearly related to NPQ. Intrinsic quantum yield of PSII (FV/FM) measured at dusk was also lower in severely stressed plants than in controls. Under maximum photosynthetic photon flux and high decarboxylation rates of organic acids, the D1 content in leaves of droughted plants showing maximal CAM activity was identical to the controls; increased drought decreased D1 content by more than 30%. Predawn samples had D1 contents similar to leaves sampled at peak irradiance, with no signs of recovery after 12 h of darkness. It is concluded that under mild water stress, early induction of CAM, together with an increased energy dissipation by the xanthophyll cycle, prevents net degradation of D1 protein; when water deficit is more severe, CAM and xanthophyll cycle capacities for energy dissipation decline, and net degradation of D1 proceeds.     

Radiation Use Efficiency,Chlorophyll Fluorescence,and Reflectance Indices Associated with Ontogenic Changes in Water-Limited Chenopodium quinoa Leaves

Net photosynthetic rate, radiation use efficiency, chlorophyll (Chl) fluorescence, photochemical reflectance index (PRI), and leaf water potential were measured during a 25-d period of progressive water deficit in quinoa plants grown in a glasshouse in order to examine effects of water stress and ontogeny. All physiological parameters except F_v/F_m were sensitive to water stress. Ontogenic variations did not exist in F_v/F_m and leaf water potential, and were moderate to high in the other parameters. The complete recovery of photosynthetic parameters after re-irrigation was related with the stability in F_v/F_m. PRI showed significant correlation with predawn leaf water potential, F_m, and midday F_v/F_m. Thus PRI and Chl fluorescence may help in assessing physiological changes in quinoa plants across different developmental stages and water status.     

Photosynthetic acclimation to low temperature by western red cedar seedlings

Imposition of low, but above freezing, temperatures resulted in a gradual increase in the cold hardiness of western red cedar seedlings. This was associated with a decrease in the maximum rates of photosynthetic CO₂ fixation and O₂ evolution, and changes in chlorophyll a fluorescence transients which indicated that photoinhibition had occurred. Maximum photosynthetic rates declined approximately 40% during cold hardening. The leaves changed colour from green to red-brown during the hardening process. The colour change was due to the synthesis of large amounts of the carotenoid rhodoxanthin. Lutein levels doubled, while chlorophyll declined slightly. Dehardening resulted in the rapid recovery of photosynthesis to control levels, the rapid disappearance of rhodoxanthin, and the return of lutein levels to control. It is suggested that rhodoxanthin accumulation at low temperature functions to decrease the light intensity reaching the photosynthetic apparatus. The combination of photoinhibition and rhodoxanthin synthesis probably serves to protect the photosynthetic capacity of the seedlings at low temperature.     

Short-term acclimation of the photosynthetic electron transfer chain to changing light: a mathematical model

Photosynthetic eukaryotes house two photosystems with distinct light absorption spectra. Natural fluctuations in light quality and quantity can lead to unbalanced or excess excitation, compromising photosynthetic efficiency and causing photodamage. Consequently, these organisms have acquired several distinct adaptive mechanisms, collectively referred to as non-photochemical quenching (NPQ) of chlorophyll fluorescence, which modulates the organization and function of the photosynthetic apparatus. The ability to monitor NPQ processes fluorometrically has led to substantial progress in elucidating the underlying molecular mechanisms. However, the relative contribution of distinct NPQ mechanisms to variable light conditions in different photosynthetic eukaryotes remains unclear. Here, we present a mathematical model of the dynamic regulation of eukaryotic photosynthesis using ordinary differential equations. We demonstrate that, for Chlamydomonas, our model recapitulates the basic fluorescence features of short-term light acclimation known as state transitions and discuss how the model can be iteratively refined by comparison with physiological experiments to further our understanding of light acclimation in different species.     

Effect of transient accumulation of anthocyanin on leaf development and photoprotection of Fagopyrum dibotrys mutant

Changes in pigments contents, leaf area, leaf dry mass per unit area (LMA), photosynthetic rate and chlorophyll a fluorescence were investigated in developing leaves of Fagopyrum dibotrys Hara. mutant. Anthocyanins transiently accumulate below the upper epidermis during leaf ontogeny of this mutant. Red leaves possessed lower Chl content, LMA, photosynthetic rate and apparent carboxylation efficiency than green leaves. However, content of anthocyanins declined and above mentioned parameters increased during further leaf development. In both red and green leaves, chronic photoinhibition did not take place according to variable to maximum chlorophyll fluorescence ratio (F_v/F_m). Red leaves had higher non-photochemical quenching (NPQ) and higher PS 2 efficiency.     

Desiccation‐induced changes in photochemical processes of photosynthesis and spectral reflectance in Nostoc commune (Cyanobacteria,Nostocales) colonies from polar regions

Cyanobacterium Nostoc commune is a species highly resistant against desiccation. In this study, we investigated changes in photochemical processes of photosynthesis and spectral reflectance indices during controlled desiccation of the colonies from Antarctica. In a dehydration process, water potential (WP) reached ?3 MPa and values of potential (F _v/F _m) and effective quantum yields (ΦPSII) of photosystem II were kept to high value until 90% of water was lost from the colony, and these values decreased rapidly by further loss of water. This indicates that the colony loses water mostly from the exopolysaccharidic envelope, not from cells during the initial part of dehydration (relative water content, RWC = 100–10%). Other suggestions of inhibition of photosynthetic processes after 90% loss of water were the increase of the chlorophyll fluorescence parameter F _p/F _s. The F _m′ was higher than F _m in hydrated colonies because of state transition which change energy distribution between PS I and PS II, but decreased to same level as F _m in dehydrated colonies. The Normalized Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI) showed concave‐ and convex‐curvilinear relationship with RWC, respectively. The changes of NDVI values were, however, statistically insignificant. PRI values were predominantly below 0 because of phycobiliprotein involvement. These results were compared with the same species in the Arctic region. This is, according to our best knowledge, the first measurement of changes in spectral reflectance indices during desiccation of cyanobacteria.