Akira Uemura

Observation of the scale of patchy stomatal behavior in leaves of Quercus crispula using an Imaging-PAM chlorophyll fluorometer

Patchy stomatal closure occurs in plants with heterobaric leaves, in which vertical extensions of bundle sheath cells delimit the mesophyll and restrict the diffusion of CO(2). The scale of patchy stomatal behavior was investigated in this study. The distribution of PSII quantum yield (Φ(II)) obtained from chlorophyll fluorescence images was used to evaluate the scale of stomatal patchiness and its relationship with leaf photosynthesis in the sun leaves of 2-year-old saplings of Quercus crispula Blume. Fluorescent patches were observed only during the day with low stomatal conductance. Comparison of numerical simulation of leaf gas exchange and chlorophyll fluorescence images showed that heterogeneous distribution of electron transport rate through PSII (J) was observed following stomatal closure with a bimodal manner under both natural and saturated photosynthetic photon flux densities. Thus, fluorescence patterns can be interpreted in terms of patchy stomatal closure. The mapping of J from chlorophyll fluorescence images showed that the scale of stomatal patchiness was approximately 2.5-fold larger than that of anatomical patches (lamina areas bounded by bundle sheath extensions within lamina). Our results suggest the spatial scale of stomatal patches in Q. crispula leaves.

Occurrence of stomatal patchiness and its spatial scale in leaves from various sizes of trees distributed in a South-east Asian tropical rainforest in Peninsular Malaysia

In this study, we demonstrated the occurrence of stomatal patchiness and its spatial scale in leaves from various sizes of trees grown in a lowland dipterocarp forest in Peninsular Malaysia. To evaluate the patterns of stomatal behavior, we used three techniques simultaneously to analyze heterobaric or homobaric leaves from five tree species ranging from 0.6 to 31 m in height: (i) diurnal changes in chlorophyll fluorescence imaging, (ii) observation and simulation of leaf gas-exchange rates and (iii) a pressure-infiltration method. Measurements were performed in situ with 1000 or 500 μmol m(-2) s(-1) photosynthetic photon flux density. Diurnal patterns in the spatial distribution of photosynthetic electron transport rate (J) mapped from chlorophyll fluorescence images, a comparison of observed and simulated leaf gas-exchange rates, and the spatial distribution of stomatal apertures obtained from the acid-fuchsin-infiltrated area showed that patchy stomatal closure coupled with severe midday depression of photosynthesis occurred in Neobalanocarpus heimii (King) Ashton, a higher canopy tree with heterobaric leaves due to the higher leaf temperature and vapor pressure deficit. However, subcanopy or understory trees showed uniform stomatal behavior throughout the day, although they also have heterobaric leaves. These results suggest that the occurrence of stomatal patchiness is determined by tree size and/or environmental conditions. The analysis of spatial scale by chlorophyll fluorescence imaging showed that several adjacent anatomical patches (lamina areas bounded by bundle-sheath extensions within the lamina) may co-operate for the distributed patterns of J and stomatal apertures.

Walker occupancy has an impact on changing airborne bacterial communities in an underground pedestrian space, as small-dust particles increased with raising both temperature and humidity

Although human occupancy is a source of airborne bacteria, the role of walkers on bacterial communities in built environments is poorly understood. Therefore, we visualized the impact of walker occupancy combined with other factors (temperature, humidity, atmospheric pressure, dust particles) on airborne bacterial features in the Sapporo underground pedestrian space in Sapporo, Japan. Air samples (n = 18; 4,800L/each sample) were collected at 8:00 h to 20:00 h on 3 days (regular sampling) and at early morning / late night (5:50 h to 7:50 h / 22:15 h to 24:45 h) on a day (baseline sampling), and the number of CFUs (colony forming units) OTUs (operational taxonomic units) and other factors were determined. The results revealed that temperature, humidity, and atmospheric pressure changed with weather. The number of walkers increased greatly in the morning and evening on each regular sampling day, although total walker numbers did not differ significantly among regular sampling days. A slight increase in small dust particles (0.3–0.5μm) was observed on the days with higher temperature regardless of regular or baseline sampling. At the period on regular sampling, CFU levels varied irregularly among days, and the OTUs of 22-phylum types were observed, with the majority being from Firmicutes or Proteobacteria (γ-), including Staphylococcus sp. derived from human individuals. The data obtained from regular samplings reveled that although no direct interaction of walker occupancy and airborne CFU and OTU features was observed upon Pearsons correlation analysis, cluster analysis indicated an obvious lineage consisting of walker occupancy, CFU numbers, OTU types, small dust particles, and seasonal factors (including temperature and humidity). Meanwhile, at the period on baseline sampling both walker and CFU numbers were similarly minimal. Taken together, the results revealed a positive correlation of walker occupancy with airborne bacteria that increased with increases in temperature and humidity in the presence of airborne small particles. Moreover, the results indicated that small dust particles at high temperature and humidity may be a crucial factor responsible for stabilizing the bacteria released from walkers in built environments. The findings presented herein advance our knowledge and understanding of the relationship between humans and bacterial communities in built environments, and will help improve public health in urban communities.

Determination of seed soundness in conifers cryptomeria japonica and chamaecyparis obtusa using narrow-multiband spectral imaging in the short-wavelength infrared range

Regeneration of planted forests of Cryptomeria japonica (sugi) and Chamaecyparis obtuse (hinoki) is the pressing importance to the forest administration in Japan. Low seed germination rate of these species, however, has hampered low-cost production of their seedlings for reforestation. The primary cause of the low germinability has been attributed to highly frequent formation of anatomically unsound seeds, which are indistinguishable from sound germinable seeds by visible observation and other common criteria such as size and weight. To establish a method for sound seed selection in these species, hyperspectral imaging technique was used to identify a wavelength range where reflectance spectra differ clearly between sound and unsound seeds. In sound seeds of both species, reflectance in a narrow waveband centered at 1,730 nm, corresponding to a lipid absorption band in the short-wavelength infrared (SWIR) range, was greatly depressed relative to that in adjacent wavebands on either side. Such depression was absent or less prominent in unsound seeds. Based on these observations, a reflectance index SQI, abbreviated for seed quality index, was formulated using reflectance at three narrow SWIR wavebands so that it represents the extent of the depression. SQI calculated from seed area-averaged reflectance spectra and spatial distribution patterns of pixelwise SQI within each seed area were both proven as reliable criteria for sound seed selection. Enrichment of sound seeds was accompanied by an increase in germination rate of the seed lot. Thus, the methods described are readily applicable toward low-cost seedling production in combination with single seed sowing technology.

Differential Analyses of the Effects of the Light Environment on Development of Deciduous Trees: Basic Studies for Tree Growth Modeling

One of the tasks of the ecophysiology team of the Ogawa Forest Reserve (OFR) project was to provide physiological bases for modeling the growth of individual trees, for incorporation into the individual-based model (IBM) of forest dynamics (see Chapter 14).

Gas Exchange and Turgor Maintenance of Tropical Tree Species in Pasoh Forest Reserve

Net photosynthetic rate (Pn), stomatal conductance (Gw), water use efficiency (WUE), and osmotic potential (ψ s0) were studied for 46 tropical tree species, including 24 tree species found in Pasoh Forest Reserve, in order to clarify their ecophysiological traits. The maximum value of Pn (Pnmax) varied from 2.5 to 24.2µmolCO2 m-2s-1 with an average of 9.1µmolCO2 m-2 s-1. The maximum value of Gw (Gwmax) varied from 30 to 1,300 molH2O m-2 s-1 with an average of 340 mmolH2O m-2 s-1. These values were relatively low compared to those of temperate tree species. Intrinsic water-use efficiency (IWUE, Pnmax/Gwmax) of the tropical species was also relatively low compared to the temperate tree species. ψ s0 of the tropical species was relatively high (less negative) compared to the temperate tree species, suggesting that the capacity of leaves to maintain positive turgor is relatively low in the tropical species. The lower photosynthetic rate in the tropical species was due not only to lower stomatal conductance, but also to lower photosynthetic efficiency, compared to the temperate species. The rapid growth of tropical tree species may be due to favorable environmental factors such as relatively constant temperature and moisture levels, which permit photosynthesis all the year-round.

A practical approach to estimate diffusional leakages of leaf chamber of open gas exchange systems using intact leaves

We propose a novel approach to determine the coefficient of CO2 diffusional leakage (k_CO2 ) in the chamber of a portable open gas exchange system (Li-6400, Li-Cor Inc., NE, USA) using intact leaves. Assuming that dark respiration rate (Rn ) is constant at various CO2 concentrations, at least in a short term, k_CO2 should be the value that makes the leak-corrected Rn constant. We used 2 representative tree species native to northern Japan, Japanese white birch (Betula platyphylla var. japonica) and Japanese oak (Quercus mongolica var. crispula), to determine k_CO2 , by measuring Rn at various CO2 concentrations. Irrespective of the species, k_CO2 estimated by the present approach was well correlated with the diffusional leak coefficient (k_flow ) estimated by the generally used approach that utilizes CO2 concentrations inside and outside the chamber based on thermally killed leaves at various flow rates. Furthermore, the present approach does not require the ambient CO2 concentration outside the chamber (Ca ) if Ca in the laboratory is stable, which provides a feasible way to correct the photosynthetic rate, taking diffusional leakage into account.

Springtime photoinhibition constrains regeneration of forest floor seedlings of Abies sachalinensis after a removal of canopy trees during winter

A clear-cutting of canopy trees during winter often causes severe foliar damage during the following spring in forest floor seedlings of Abies sachalinensis, a typical shade-tolerant evergreen coniferous species. The maximum photochemical efficiency of photosystem II after an overnight dark adaptation showed a temporary decrease immediately before budbreak in 1-year-old shoots of A. sachalinensis seedlings grown under full sunlight in a nursery, suggesting “springtime photoinhibition” related to the phenology of evergreen coniferous species. In the field, a greater rate of canopy tree cutting during winter was associated with more severe photoinhibition in the following spring, immediately before budbreak, which subsequently resulted in a reduction in carbon gain in 1-year-old shoots, and consequently suppressed the growth of current-year shoots. Although photoinhibition under low temperature is a well-known factor to determine the survival rate of tree seedlings during winter in cool regions, the present study additionally proposes that the temporary increase in the susceptibility to photoinhibition in springtime i.e. “springtime photoinhibition” would be a constraint for the regeneration of coniferous seedlings especially when the canopy trees are removed during winter.

The effect of the planting depth of cuttings on biomass of short rotation willow

ABSTRACT In order to investigate how the depth to which a cutting is inserted into the ground influences biomass of short-rotation coppice willows, 1-year-old cuttings from three clones each of Salix pet-susu and Salix sachalinensis were planted and harvested after two-seasons growth under natural conditions. All cuttings were 20 cm long, with either 18 or 10 cm below ground level (referred to as deep planting [DP] and shallow planting [SP], respectively, hereafter). Aboveground dry biomass from DP was 40% greater than from SP, although root biomass did not differ between the two treatments and shoot number per cutting was lower for DP than SP. The roots of the DP cutting were found deeper in the soil than those of SP cutting, suggesting that sustained soil water supply resulted in the higher aboveground biomass.

Leaf Physiological Adjustments to Changing Lights: Partitioning the Heterogeneous Resources across Tree Species

Rain forest trees with various light requirements exhibit a high variation in their physiology and morphology as they encounter contrasting light environments, contributing to higher leaf carbon gain in each environment. A desire to understand the species-specific variations of capturing and using of light resources in terms of photosynthetic processes provides the setting for this chapter. Both niche partitioning and chance effects in the distribution of tropical trees are widely recognized. The objective of this chapter is to clarify tree responses at the single leaf and whole plant levels for the spatial and temporal changes of lights, providing an improved background of ideas on rain forest dynamics and coexistence and an improved plan for the sustainable forest management and conservation. Recent evidences that the ecophysiological adjustments of plant to changing lights influence replacement success under the changing environments and tropical forest dynamics, are reviewed briefly.