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Sod culture (SC) and no tillage (NT) are modern orchard management systems, and are two different bases for the sustainable development and production of citrus orchards in Taiwan. However, there is no information about the efficiency of either NT or SC on the photosynthetic physiology of farmed citrus under different seasons and varying light intensities. The objective of this study was to clarify the impacts of SC and NT under eco-friendly farming management on the photosynthetic apparatus of an important plantation citrus species in response to varying light intensities over the seasons. The results showed that Rd (dark respiration rate of CO2), Qy (light quantum yield of CO2), LCP (light compensation point), Amax (maximum net assimilation of CO2), and Fv/Fm values of citrus plants under SC were somewhat higher under NT in the same season, particularly in the fall and in winter. As light intensity increased from 200 to 2000 μmol photon m−2 s−1 PPFD, higher Pn (net photosynthesis rate), Gs (stomatal conductance), ETR (electron transport rate), NPQ (non-photochemical quenching), and Fv/Fm (potential quantum efficiency of PSII) values were observed in spring and summer compared to the fall and winter, and increasing NPQ and decreasing Fv/Fm values were observed in all seasons. Positive and significant correlations were shown between the Pn and Gs under NT and SC in all seasons with all light illuminations, whereas significant and negative relationships were observed between the ETR and NPQ under NT in fall and winter at 1200~2000 PPFD. In short, ETR was useful for non-destructive estimations of Pn and NPQ since these indices were significantly and positively correlated with ETR in citrus leaves exposed to 0~1200 PPFD in all seasons and 1200~2000 PPFD in spring, the fall, and winter, providing a quick means to identify the physiological condition of plants under various seasons and tillages. The precise management of photosynthetic parameters such as ETR in response to light irradiances under varied seasons also provides implications for sustainable citrus production for tillage cropping systems in future higher CO2 and potentially wetter or drier environments. The tillages may hold promise for maximizing the economic efficiency of the growth and development of citrus plants grown in the field.

The changes and responses in the chlorophyll (Chl) fluorescence (ChlF) components were studied on the red and green parts of leaves in three Coleus blumei varieties under different light intensities. Chl a, carotenoids (Car), and SPAD were linearly, positively, and significantly correlated with total Chl [i.e., Chl (a+b)] of red and green leaves. Significant differences in Chl and Car contents were noted between differentially pigmented sectors of the leaf, but no anthocyanin content was found in the green parts compared to red leaves. Values of minimal and maximal fluorescence yields in dark- and light-adapted states in both red and green leaves were all positively and significantly correlated with Chl contents under dark conditions and all PPFD treatments for 20 min. Assessing the ChlF parameters under PPFD variations is an important tool for finding improved photosynthetic productivity of plants.

The rapid light response of electron transport rate (ETRR), obtained from chlorophyll fluorescence parameters by short illumination periods (10–30 s) at each light level, can provide a rapid and easy measurement of photosynthetic light response in plants. However, the relationship between ETRR and the steady-state light response of CO2 exchange rate (AS) of terrestrial plants has not been studied in detail. In this study, we compared the ETRR and AS for five woody and four fern species with different light and/or water adaptations. Under well-watered conditions, a constant temperature (25 °C) and with stomatal conductance (gs) not being a main limiting factor for photosynthesis, ETRR and AS were closely related, even when merging data for regression analysis for a species grown under different light conditions and measured under different light intensity and air humidity. However, when Alnus formosana was treated with low soil water and air humidity, because of the decrease in AS mainly due to stomatal closure, the ETRR–AS relation was not so close. In addition, at both 100 and 2000 μmol m−2 s−1 photosynthetic photon flux density (PPFD), ETRR and AS were significantly correlated within a plant group (i.e., woody plants and ferns) regardless of the broad difference in AS due to different species or environmental factors. The results indicate that the relationship between the ETRR and AS is varied by species. We concluded that 1) ETRR could reflect the variation in AS at each irradiance level within a species under well-watered conditions and 2) ETRR at 100 μmol m−2 s−1 PPFD (as the efficiency of light capture) or 2000 μmol m−2 s−1 PPFD (as a maximum photosynthetic parameter) could be used to compare the photosynthetic capacity within a plant group, such as woody plants and ferns.

Limited information is available regarding the physiology of squash plants grown under waterlogging stress. The objectives of this study were to investigate the growth and physiological performances of three cucurbit species, Cucurbita maxima cultivar (cv.) OK-101 (OK) and Cucurbita moschata cv. Early Price (EP) and Strong Man (SM), in response to waterlogging conditions, and to develop a precise, integrated, and quantitative non-destructive measurement of squash genotypes under stress. All tested plants were grown in a growth chamber under optimal irrigation and growth conditions for a month, and the pot plants were then subjected to non-waterlogging (control) and waterlogging treatments for periods of 1, 3, 7, and 13 days (d), followed by a 3-d post-waterlogging recovery period after water drainage. Plants with phenotypes, such as fresh weight (FW), dry weight (DW), and dry matter (DM) of shoots and roots, and various physiological systems, including relative water content (RWC), soil and plant analysis development (SPAD) chlorophyll meter, ratio of variable/maximal fluorescence (Fv/Fm), quantum photosynthetic yield (YII), normalized difference vegetation index (NDVI), and photochemical reflectance index (PRI) values, responded differently to waterlogging stress in accordance with the duration of the stress period and subsequent recovery period. When plants were treated with stress for 13 d, all plants exhibited harmful effects to their leaves compared with the control, but EP squash grew better than SM and OK squashes and exhibited stronger tolerance to waterlogging and showed less injury. Changes in the fresh weight, dry weight, and dry matter of shoots and roots indicated that OK plants suffered more severely than EP plants at the 3-d drainage period. The values of RWC, SPAD, Fv/Fm, YII, NDVI, and PRI in both SM and OK plants remarkably decreased at waterlogging at the 13-d time point compared with controls under identical time periods. However, the increased levels of SPAD, Fv/Fm, YII, NDVI, and PRI observed on 7 d or 13 d of waterlogging afforded the EP plant leaf with improved waterlogged tolerance. Significant and positive correlations were observed among NDVI and PRI with SPAD, Fv/Fm, and YII, indicating that these photosynthetic indices can be useful for developing non-destructive estimations of chlorophyll content in squashes when screening for waterlogging-tolerant plants, for establishing development practices for their cultivation in fields, and for enhanced cultivation during waterlogging in frequently flooded areas.

The objective of this work was to study changes in the chlorophyll fluorescence (ChlF) components of two sweet potatoes (Ipomoea batatas L. Lam) cultivars ‘Taoyaun 2’ (green leaf) and ‘CN1927’ (yellow leaf) in response to varying light intensities and temperatures. Cuttings were grown in potting soil under a controlled greenhouse for 4 weeks and moved to a dark room overnight. Plants were then illuminated with 1,000 and 2,000 μmol m−2 s−1 of photosynthetic photon flux density (PPFD) at 10, 25, and 35°C for 30 min with a cool light source, followed by a 30 min dark recovery period at each measured temperature. ChlF was measured immediately before illumination and every 2~5 min during illumination until the end of dark recovery. All measurements were performed at 2 min intervals during the temperature exposure period. The accumulation of chlorophyll affected the leaf colors, and those ChlF indices of yellow- and green-leaved plants treated under various temperatures in response to various light intensities over time, showing wide variations in maximal chlorophyll fluorescence Fv/Fm (in darkness), Fv’/Fm’ (in the light), and non-photochemical fluorescence quenching (NPQ) levels. Moreover, green-leaved plants showed greater the fraction of excess energy in PS II (E) and fraction of light absorbed in PSII antennae (P) than yellow-leaved plants, but lower the fraction of light absorbed in PSII antennae that is dissipated thermally (D) than yellow-leaved plants at 35°C under 1,000 μmol m−2 s−1. As temperature increased, P values of all plants increased but D values decreased. The values of qE% in green leaves were significantly higher than those in yellow leaves, whereas qI% in yellow leaves was significantly higher than in green leaves under 2,000 μmol m−2 s−1 at all temperatures. There were significant and negative correlations of NPQ with Fv’/Fm’ and ΔF/Fm’, and of D with P of green leaves, but significant and positive relationship was detected between E and P of green-leaved plants. Manipulation of light harvesting and its regulation by photo-protection might be a key to increase bioenergy and food crop yields. The effective management of ChlF parameters in response to the light intensity provides a better understanding of the photosynthetic characteristics of leafy vegetables grown in controlled environments with various combinations of varying temperatures and high light intensities.

The effects of water stress on photosynthetic pigments and secondary metabolites of two varieties of greenand purple-leaf Perilla frutescens plants were studied. Plants were grown in plastic pots for 14 days followedby water stress treatment for 10 days in a greenhouse. The trends and rates of soil water potential (SWP), leafwater content (LWC), and the maximum photochemical quantum yield (Fv/Fm) values in these two varietieswere similar as the period of water stress increased from 1 to 8 days. The responses of SWP, LWC, and Fv/Fmvalues to water stress treatment of both varieties were adapted to a water stress period of 4 days. Purple plantsexhibited significantly higher levels of anthocyanins and flavonoids than green plants under drought conditions.However, chlorophyll (Chl) a + b and carotenoids (Car) in the two varieties showed no significant differences inall water-depletion periods. The adjusted normalized difference vegetation index was significantly correlatedwith leaf Chl a+b, and the photochemical reflectance index was significantly correlated with Car in both species,and these can be used as indicators to characterize the physiology of these plants.

The spider mite Tetranychus urticae Koch is emerging as a major problem in Jatropha curcas cultivation. The goal of this study was to investigate the photosynthetic responses of Jatropha to spider mite infestation. Leaf CO2 assimilation rate, stomatal conductance, transpiration, intracellular CO2 concentration, and instantaneous carboxylation efficiency significantly decreased in mite-infested leaves compared with controls. Lower water content and specific leaf area of the mite-infested leaves were positively related to symptoms of wrinkling and curling. Leaf electrolyte leakage remained unchanged in the mite-infested leaves, revealing no effect on leaf membrane integrity. Leaves exhibited reductions in soluble protein and soluble sugar in association with photosynthetic impairment. Although decreases in photochemical activity and chlorophyll fluorescence parameters suggested damage to the photosynthetic apparatus, although there were no measurable reductions in chlorophyll or carotenoid contents associated with photosynthetic apparatus impairment. The decrease in the leaf CO2 assimilation rate was partially attributed to stomatal and metabolic limitations in the mite-infested leaves.

Previous studies of the impacts of galls on host leaf photosynthesis do not suggest any general trends, with a reported range of effects from negative to positive. In this study, photosynthetic characteristics such as chlorophyll fluorescence (Fv/Fm), photosynthetic capacity, and stomata conductance were determined in two types of fruit-like galls (red ovoid and green obovate galls) induced by Daphnephila taiwanensis and Daphnephila sueyenae, respectively, in order to investigate whether the number of galls affects the photosynthesis of galled leaves of Machilus thunbergii. In 2008, chlorophyll fluorescence and photosynthetic capacity were negatively correlated with gall numbers, non-significantly and significantly, respectively, whereas stomata conductance was positively but non-significantly correlated with gall numbers. In 2009, photosynthesis capacity and stomata conductance were negatively, but non-significantly, correlated with gall numbers. Results imply that photosynthesis in M. thunbergii leaves is slightly affected by the number of cecidomyiid insect galls, and that the higher the gall number, the greater the negative effect that galls have on host leaf photosynthesis and subsequent infection.

We aimed to find out relations among nonphotochemical quenching (NPQ), gross photosynthetic rate (PG), and photoinhibition during photosynthetic light induction in three woody species (one pioneer tree and two understory shrubs) and four ferns adapted to different light regimes. Pot-grown plants received 100% and/or 10% sunlight according to their light-adaptation capabilities. After at least four months of light acclimation, CO2 exchange and chlorophyll fluorescence were measured simultaneously in the laboratory. We found that during light induction the formation and relaxation of the transient NPQ was closely related to light intensity, light-adaption capability of species, and PG. NPQ with all treatments increased rapidly within the first 1–2 min of the light induction. Thereafter, only species with high PG and electron transport rate (ETR), i.e., one pioneer tree and one mild shade-adapted fern, showed NPQ relaxing rapidly to a low steady-state level within 6–8 min under PPFD of 100 μmol(photon) m−2 s−1 and ambient CO2 concentration. Leaves with low PGand ETR, regardless of species characteristics or inhibition by low CO2 concentration, showed slow or none NPQ relaxation up to 20 min after the start of low light induction. In contrast, NPQ increased slowly to a steady state (one pioneer tree) or it did not reach the steady state (the others) from 2 to 30 min under PPFD of 2,000 μmol m−2 s−1. Under high excess of light energy, species adapted to or plants acclimated to high light exhibited high NPQ at the initial 1 or 2 min, and showed low photoinhibition after 30 min of light induction. The value of fastest-developing NPQ can be quickly and easily obtained and might be useful for physiological studies.

We examined the feasibility of using chlorophyll fluorescence to estimate CO2 exchange (A) of C4 perennial grasses under different environmental as well as physiologic conditions using Pennisetum purpureum and Miscanthus floridulus, capable of year-round growth, to determine the association of electron transport rate (ETR) and A. The grasses were fertilized with three levels of nitrogen, and measurement involved the top two fully expanded leaves, with chlorophyll content 0.18–0.55 g m−2. Chlorophyll fluorescence, CO2 and H2O exchange were measured simultaneously at four seasonal temperatures (30–15 °C, September–January), six levels of photosynthetic photon flux density (PPFD) (0–2,000 μmol m−2 s−1) and two levels of relative humidity [60 % (15–30 °C) and 40 % (30 °C alone)]. Variables were recorded when A was stable. Most leaves with high chlorophyll content showed high A at the same PPFD and seasonal temperature. Despite a broad range of A obtained because of both stomatal and non-stomatal factors, ETR was still highly correlated linearly with net photosynthetic rates, when combining data for the same species for analysis. Thus, ETR could be used to assess the dynamic A of C4 perennial species through different seasons, even under varied light intensity, seasonal temperature, humidity, nitrogen fertilization and phenological stage.

The objectives of this study were to characterize the fluorescence and spectral reflectance patterns of galled and nongalled portions of leaves of Machilus thunbergii and to understand changes in metabolism subsequent to gall development on the leaf surface. The results showed that the reflectance values of galls at 280 nm (R280) and 320 nm (R320) were greater than those for normal leaves; this was hypothesized to minimize ultraviolet light damage. The lower photochemical reflectance index and higher red-green ratio in galls than leaves indicated that xanthophyll cycle pigments and the anthocyanin content were higher in galls than in leaves. In contrast, the lower adjusted normalized difference vegetation index (aNDVI) and cold hard band for galls indicated lower maximum quantum efficiencies for photosystem II (Fv/Fm), chlorophyll contents, and pigment-protein complexes in galls than in leaves. Overall, the fluorescence and reflectance analyses suggested that insect infestations reduce photosynthetic effi...

Plants of the genus Calathea possess many leaf colors, and they are economically important because they are widely used as ornamentals for interior landscaping. Physiological performances and photosynthetic capacities of C. insignis and C. makoyana were investigated. The photosynthetic efficiencies of C. insignis and C. makoyana were significantly increased when the photosynthetic photon flux density (PPFD) increased from 0 to 600 μmol photons·m−2·s−1 and became saturated with a further increase in the PPFD. The two Calathea species had lower values of both the light saturation point and maximal photosynthetic rate, which indicated that they are shade plants. No significant differences in predawn Fv/Fm values (close to 0.8) were observed between dark-green (DG) and light-green (LG) leaf sectors in all tested leaves. However, the effective quantum yield of photosystem II largely decreased as the PPFD increased. An increase in the apparent photosynthetic electron transport rate was observed in both species to a maximum at 600 μmol·m−2·s−1 PPFD, following by a decrease to 1500 μmol·m−2·s−1 PPFD. Compared to LG leaf extracts, DG leaf extracts contained higher levels of chlorophyll (Chl) a, Chl b, Chls a + b, carotenoids (Cars), anthocyanins (Ants), flavonoids (Flas), and polyphenols (PPs) in all plants, except for the Ant, Fla and PP contents of C. insignis plants. Calathea insignis also contained significantly higher levels of total protein than did C. makoyana. The adjusted normalized difference vegetation index (NDVI), photochemical reflectance index (PRI), red-green, and flavonol index (FlavI) were significantly correlated to leaf Chls a + b, Cars, Ants, and Flas in C. makoyana, respectively, and can be used as indicators to characterize the physiology of these plants.

Background The source and sink relationships between insect-induced galls and host plant leaves are interesting. In this research, we collected cup-like galls induced by Bruggmanniella sp. (Diptera: Cecidomyiidae) on host leaves of Litsea acuminata and assessed them to investigate source-sink relationships between galls and host leaves. We characterized several of their photosynthetic characteristics including chlorophyll fluorescence (Fv/Fm), stomatal conductance, and photosynthetic capacity, biochemical components such as total soluble sugar, starches, free amino acids, and soluble proteins. The structural analyses were performed under confocal, light, and scanning electron microscopies. Results Compared with host leaves, galls exhibited slightly lower chlorophyll fluorescence; however, stomatal conductance and photosynthetic capacity were not detected at all. Galls accumulated higher total soluble sugars and free amino acids but less soluble proteins than host leaves. No stomata was observed on exterior or interior gall surfaces under light or scanning electron microscopy, but their inner surfaces were covered with fungal hyphae. Confocal imagery showed a gradient of chloroplasts distribution between gall outer and inner surfaces. Conclusions Our results strongly suggest that leaf-derived cecidomyiid galls are a type of chlorophyll-deficient non-leaf green tissue and consists on a novel sink in L. acuminate.