Differences in Characteristics of Photosynthesis and Nitrogen Utilization in Leaves of the Black Locust (Robinia pseudoacacia L.) According to Leaf Position

Abstract

Robinia pseudoacacia L. has been widely planted worldwide for a variety of purposes, but it is a nonindigenous species currently invading the central part of Japanese river terraces. To understand and control this invasion, we investigated how this species invests nitrogen resources in different functions depending on the leaf location, and how these resources are used in physiological reactions such as photosynthesis. The Tama river terrace was examined in Tokyo, Japan. The leaf nitrogen (N) concentration, chlorophyll (Chl) concentration, Chl a/b ratio, leaf mass per unit area (LMA) and ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCo) concentration were all significantly lower in shade leaves than in leaves exposed to the sun. Conversely, the net photosynthetic rate in saturated light conditions (Pmax), the net photosynthetic rate under enhanced CO2 concentration and light saturation (Amax), the maximum carboxylation rate of RuBisCo (Vcmax) and the maximum rate of electron transport driving RUBP regeneration (Jmax) were all significantly lower in shade leaves than in leaves exposed to the sun. We also found that RuBisCo/N and Chl/N were significantly less in shade leaves, and values of Jmax/N, Vcmax/N less in shade leaves than in sun leaves, but not significantly. Allocation of nitrogen in leaves to photosynthetic proteins, RuBisCo (NR) was broadly less in shade leaves, and NL (light-harvesting complex: LHC, photosystem I and II: PSI and PSII) and NE (electron transport) were also lower. The N remaining was much greater in shade leaves than in sun leaves. We suggest that N remobilization from RuBisCo is more efficient than remobilization from proteins of NE, and from NL. This study shows that R. pseudoacacia has an enhanced ability to adapt to environmental changes via characteristic changes in N allocation trade-offs and physiological traits in its sun and shade leaves.

Morphoanatomical Responses and Stomatal Conductance in Shaded and Sun-Exposed Broussonetia papyrifera Seedlings

“…It supports the higher leaf mass per area (LMA) observed in the sun-exposed than in the shaded condition. Sun leaves often have higher LMA than shade leaves, and such a characteristic enhances photosynthetic rates on an area basis (Choi et al 2021). This result suggests that the seedlings are allocating more resources to producing denser and thicker leaves in response to increased light availability.…”

Photosynthetic nitrogen utilization of Robinia pseudoacacia, an invasive species, grown in contrasting light conditions: A leaf scale approach

“…The photosynthetic rate was determined with a portable photosynthesis transpiration system (LI‐6400, LiCor, Nebraska, USA) with a blue light LED source (LI‐6400‐02) attached. P sat and gs (stomatal conductance) were determined under steady leaf temperature (25°C), and PPFD was around 1400 μmol m −2 s −1 as previously determined (Choi et al, 2021; Koike et al, 2009). The maximum photosynthetic rate of light and CO 2 saturation ( P max ) was determined at CO 2 1700 μmol mol −1 , PPFD of 1500 μmol m −2 s −1 , and a leaf temperature of 25°C.…”

“…Generally, the photosynthetic rate is positively correlated with N in leaves (Hikosaka, 2010; Larcher, 2003); about 70% of leaf N is allocated to photosynthesis‐related proteins (Evans, 1989). When tree seedlings grow under shady conditions, leaf N is mainly allocated to light‐harvesting proteins on thylakoid membrane (Choi et al, 2021; Kitaoka & Koike, 2004).…”

Assessing Water Relations and Carbon Dynamics of Pinus taeda Branches Undergoing Shade-Induced Mortality

“…Instead, it may be attributed to the decreased capacity to fix CO 2 by the branch under shaded conditions [59]. Past studies have reported decreased Rubisco and leaf nitrogen content, resulting in reduced CO 2 fixation under shade conditions [60]. The reduction in g s could also be due to a higher ratio of intercellular CO 2 concentration (C i ) to ambient CO 2 concentration (C a ).…”