Relationships of photosynthetic capacity to PSII efficiency and to photochemical reflectance index of Pinus taiwanensis through different seasons at high and low elevations of sub-tropical Taiwan

Abstract

We investigated the relationships of photosynthetic capacity (P (nsat), near light-saturated net photosynthetic rate measured at 1,200 mu mol m(-2) s(-1) PPFD) to photosystem II efficiency (F (v)/F (m)) and to photochemical reflectance index [PRI = (R (531) - R (570))/(R (531) + R (570))] of Pinus taiwanensis Hay. needles at high (2,600 m a.s.l) and low-elevation (800 m a.s.l) sites through different seasons. Results indicate that at high-elevation site, P (nsat), F (v)/F (m) and PRI (both measured at predawn) paralleled in general with the air temperature. On the coolest measuring day with the minimum air temperature dropping to -2A degrees C, P (nsat) could decrease to ca. 15% of its highest value, which was measured in autumn. At low-elevation site, with the minimum air temperature of 10-12A degrees C in cooler season and almost no seasonal variation of F (v)/F (m), P (nsat) dropped to ca. 65% of its highest value and PRI decreased ca. 0.02 in winter. Even though seasonal variation of P (nsat) was affected by many factors, it was still closely related to PRI based on statistical analyses using data from both sites, through different seasons. On the contrary, seasonal variation of F (v)/F (m) of P. taiwanensis needles was influenced mainly by low temperature at high elevation. Therefore, the correlation of P (nsat) - F (v)/F (m) was lower than that of P (nsat) - PRI when data combined from both high- and low-elevation sites were analyzed. It is concluded that predawn PRI could be used as an indicator to estimate the seasonal potential of photosynthetic capacity of P. taiwanensis grown at low- and high-elevations of sub-tropical Taiwan

Ability of the Photochemical Reflectance Index to Track Light Use Efficiency for a Sub-Tropical Planted Coniferous Forest

“…To our knowledge, only one study in a Pinus taiwanensis forest pointed out that PRI is more sensitive than photosystem II efficiency to water deficits, and is closely related to photosynthetic capacity at both high-and low-elevation sites in different seasons [92]. In our study, the strongest correlation between PRI and LUE was found during the dry season (Figures 8 and 9 and Table 1), which confirms the sensitivity of PRI to water and heat stress previously reported for tropical and Mediterranean forests [87][88][89][90][91][93][94][95] and its ability to detect variations of LUE under stress conditions similar to that in other forests.…”

Relationships between photosystem II efficiency and photochemical reflectance index under different levels of illumination: comparison among species grown at high- and low elevations through different seasons

“…Few measurements were made in the summer because of road damage by thunderstorms, typhoons and heavy rains (Weng et al 2009). Sampling procedures were the same as those used in our previous studies (Weng et al 2006b(Weng et al , 2009): current-year shoots were sampled from a southeast-facing open stand (Miscanthus) or southeastfacing branches of 2-3 m high trees growing in a mixed open stand. Shoot samples were collected before sunrise at 0600-0630 h and immediately re-cut under water.…”

“…zeaxanthin levels (Demmig et al 1988;Adams et al 2004). The relationships between photochemical efficiency and PRI and/or between net CO 2 uptake and PRI have been examined by different irradiance levels (Peñuelas et al 1994;Gamon et al 1997;Nakaji et al 2006;Weng et al 2006aWeng et al , 2010, seasons (Nakaji et al 2006(Nakaji et al , 2007Weng et al 2006bWeng et al , 2009Weng et al , 2010 and species (Gamon et al 1997;Trotter et al 2002;Guo and Trotter 2004;Weng et al 2006a, b), at leaf to satellite scales (Garbulsky et al 2011).…”

“…These species can maintain green leaves during cold seasons from low land to subalpine zones of Taiwan. Their photosynthesis would face various temperature conditions at different elevations and in different seasons (Weng et al 2006b(Weng et al , 2009). Moreover, leaf (needle) structure and biochemical components of plants may vary with elevation and could influence leaf spectral reflectance (Filella and Peñuelas 1999;Richardson et al 2001;Martin et al 2007).…”

“…Photosynthesis, one of the major determinants of biomass production and terrestrial carbon budgets, is influenced by many environmental and physiological factors (see Berry and Downton 1982) and varies by habitat, season and diurnal course (Gamon et al 1997;Weng et al 2009;Nakaji et al 2006). To monitor spatial and temporal variations of photosynthetic capacity in natural conditions, researchers have developed noninvasive remote-sensing techniques.…”