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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.

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.

Mango is a chilling-sensitive evergreen fruit tree of tropical origin. In different seasons, mango leaves with different predawn F v/F m, due to the variation of minimum air temperature before sunrise (T min), were selected to measure actual quantum efficiency of PSII $$ (\Updelta F/F^{\prime}_{\text{m}} ) $$ at various temperatures and light intensities under natural and artificial conditions. Relationships of PSII efficiency (ΦPSII, F v/F m at predawn or $$ \Updelta F/F^{\prime}_{\text{m}} $$ during illumination) and photosynthetic photon flux density (PPFD or E) measured under a given temperature of artificial condition, could be fitted well by equations: ΦPSII = a 1 + b 1 × c 1 and ΦPSII = a 2 + b 2 × E/(c 2 + E). Both a 1 + b 1 and a 2 were close to the measured predawn F v/F m, and b 1 and b 2 showed positive and negative linear correlation, respectively, with predawn F v/F m. Both c 1 and c 2 showed a significant curvilinear correlation with temperature during illumination (T), and predawn F v/F m showed a significant curvilinear correlation with T min. By combining the above relationships, we obtained 2 empirical regression models: ΦPSII = −0.016 + 0.129 × (1.036 − 6.359/T min) + [0.019 + 0.866 × (1.036 − 6.359/T min)] × (1.004 − 0.153/T) E and ΦPSII = −0.003 + 1.013 × (1.036 − 6.359/T min) + [0.093 − 1.194 × (1.036 − 6.359/T min)] × E/[(24.690 × exp0.095T ) + E]. ΦPSII estimated from these 2 equations was highly correlated with measured ΦPSII (r 2 = 0.920 and 0.930, respectively, P

We aimed to understand the relation of photosynthetic rate (A) with g(s) and electron transport rate (ETR) in species of great taxonomic range and light adaptation capability during photosynthetic light induction. We studied three woody species (Alnus formosana, Ardisia crenata and Ardisia cornudentata) and four fern species (Pyrrosia lingus, Asplenium antiquum, Diplazium donianum and Archangiopteris somai) with different light adaptation capabilities. Pot-grown materials received 100 and/or 10% sunlight according to their light adaptation capabilities. At least 4 months after light acclimation, CO(2) and H(2)O exchange and chlorophyll fluorescence were measured simultaneously by equipment in the laboratory. In plants adapted or acclimated to low light, dark-adapted leaves exposed to 500 or 2000 µmol m(-2) s(-1) photosynthetic photon flux (PPF) for 30 min showed low gross photosynthetic rate (P(g)) and short time required to reach 90% of maximum P(g) (). At the initiation of illumination, two broad-leaved understory shrubs and the four ferns, especially ferns adapted to heavy shade, showed higher stomatal conductance (g(s)) than pioneer tree species; materials with higher g(s) had short at both 500 and 2000 µmol m(-2) s(-1) PPF. With 500 or 2000 µmol m(-2) s(-1) PPF, the g(s) for the three woody species increased from 2 to 30 min after the start of illumination, but little change in the g(s) of the four ferns. Thus, P(g) and g(s) were not correlated for all material measured at the same PPF and induction time. However, P(g) was positively correlated with ETR, even though CO(2) assimilation may be influenced by stomatal, biochemical and photoinhibitory limitations. In addition, was closely related to time required to reach 90% maximal ETR for all materials and with two levels of PPF combined. Thus, ETR is a good indicator for estimating the light induction of photosynthetic rate of species, across a wide taxonomic range and light adaptation and acclimation capability.

Previously, we found a significant association between photosystem II efficiency (ΦPSII) and photochemical reflectance index (PRI) measured at predawn among different species at different elevations and throughout several seasons. However, this relationship has not been evaluated under varied levels of illumination. Here, we used the Taiwan species Pinus taiwanensis (a conifer distributed at 750–3,000 m a.s.l.), Stranvaesia niitakayamensis (an evergreen tree, 1,700–3,100 m) and two Miscanthus spp. (perennial C4 Gramineae, coastline–3,200 m) to elucidate the ΦPSII–PRI relationship. We studied six levels of photosynthetic photon flux density (PPFD) (0, 200, 400, 800, 1,200 and 2,000 μmol m−2 s−1) over several growth seasons at high (2,600 m a.s.l.) and low (800 m a.s.l.) elevation sites. In comparing the same species or genus, ΦPSII and PRI were closely correlated in darkness or under the same level of PPFD, with data obtained from different seasons and elevations pooled for regression analysis. Because both the intercept and slope of the ΦPSII–PRI equation showed a negative curvilinear correlation with PPFD, we could fit an empirical regression model, ΦPSII = c + d·ln(PPFD) + e·[ln(PPFD)]2 + f·PRI + g·PRI·ln(PPFD) + h·PRI·[ln(PPFD)]2, for multiple regression analysis. Using this model, we found a close correlation between the estimated and measured ΦPSII (r 2 = 0.842−0.937, P