Effects of Throughfall Exclusion on Photosynthetic Traits in Mature Japanese Cedar (Cryptomeria japonica (L. f.) D. Don.)

Abstract

As climate change progresses, it is becoming more crucial to understand how timber species respond to increased drought frequency and severity. Photosynthetic traits in a 40-year-old clonal Japanese cedar (Cryptomeria japonica) plantation were assessed under artificial drought stress using a roof to exclude rainfall and a control with no exclusion. C. japonica is a commercial tree that is native to Japan and has high growth on mesic sites. The maximum carboxylation rate (Vcmax), maximum electron transfer rate (Jmax), and dark respiration rate (Rd) in current-year shoots in the upper canopy were determined from spring to autumn over two growing seasons. In addition, the photosynthetic rate at light saturation (Pmax), stomatal conductance (gs), and intrinsic water use efficiency (WUEi) were measured in the morning and afternoon during the same period. Leaf mass per unit area (LMA) and nitrogen concentration (N) were also measured. The values of Vcmax, Jmax, Rd, N, and LMA did not differ between the two plots. By contrast, significantly lower Pmax and gs and higher WUEi were found in the drought plot, and the reduction in Pmax was accompanied by low gs values. Midday depressions in Pmax and gs were more pronounced in the drought plot relative to the control and were related to higher WUEi. Under drought conditions, mature Japanese cedar experienced little change in photosynthetic capacity, foliar N, or LMA, but they did tend to close the stomata to regulate transpiration, thus avoiding drought-induced damage to the photosynthetic machinery and improving WUEi.

The effects of soil drought stress on growth characteristics, root system, and tissue anatomy of Pinus sylvestris var. mongolica

“…The study of leaf microstructure is helpful in understanding the response of plants to drought stress and provides the basis for further research. The results of the scanning electron microscope showed that the size of stomata and opening of the needles were significantly reduced, which was consistent with the results of some previous studies on Cryptomeria japonica , Larix kaempferi and some other species of forest trees ( Bhusal et al, 2020 ; Kenzo et al, 2021 ; Nadia et al, 2021 ). Furthermore, this study found that the tracheid diameter and tracheid wall thickness of roots, stems, and needles gradually decreased with the deepening of the drought.…”

Verification of our empirical understanding of the physiology and ecology of two contrasting plantation species using a trait database

“…Similar less sensitivity of stomatal response of mature C . japonica trees has recently been reported under artificial soil drying experiments [ 78 ].…”

Diurnal Change of the Photosynthetic Light-Response Curve of Buckbean (Menyanthes trifoliata), an Emergent Aquatic Plant

“…However, although much information is available on the midday depression of photosynthesis in rice plants (Oryza sativa L.) [11,27,28,66,67], there is limited information on wild aquatic plant species. This situation contrasts with the plentiful information on terrestrial plants in diverse habitats, including both woody species [30,31,37,42,43,54,55,58,61,[68][69][70] and herbs [39,56,60,71,72]. Previous studies on midday depression of emergent plants are equivocal.…”

“…Midday depression of photosynthesis is a phenomenon where photosynthetic rate decreases during the midday hours when light is not a limiting factor for photosynthesis [6,8,11,21,50,[54][55][56][57][58]. The degree of photosynthetic limitation is affected not only by the atmospheric environment surrounding leaves, but also by the soil water content and resultant whole-plant water status [21,31,32,37,38,[41][42][43]48,50,54,[59][60][61][62][63][64][65]. Thus, it is expected that plants in environments with different water availability will show different degrees of midday depression.…”