Photosynthetic and Growth Responses in a Pioneer Tree (Japanese White Birch) and Competitive Perennial Weeds (Eupatorium sp.) Grown Under Different Regimes With Limited Water Supply to Waterlogging

Abstract

For a successful natural regeneration of Japanese white birch (Betula platyphylla var. japonica), competitive vegetation should be managed. Here, we clarified how soil water condition modifies the competitiveness of Japanese white birch against perennial weeds, Eupatorium species, based on an ecophysiological approach combining a glasshouse experiment and a field survey. We investigated photosynthetic and growth responses to various water regimes from water deficit to waterlogging (two times-a-week irrigation, three times-a-week irrigation, half waterlogging, and full waterlogging) in pot-grown seedlings of Japanese white birch and the competitive weed Eupatorium makinoi. The ratio of seedling height of Japanese white birch to seedling height of E. makinoi showed a decreasing trend from two times-a-week irrigation to full waterlogging, which suggests a lower competitiveness for light resource in Japanese white birch with increasing soil wetness. The maximum rate of Rubisco carboxylation (Vc,max) based on unit N was lower in waterlogging treatments than in two times- and three times-a-week irrigation in Japanese white birch, whereas E. makinoi showed the opposite response. This suggests that N partitioning into Rubisco and/or Rubisco activation might be suppressed in Japanese white birch but enhanced in E. makinoi under waterlogging. The maximum photochemical efficiency of photosystem II (Fv/Fm) was also lower in seedlings of Japanese white birch grown under waterlogging treatments. We further conducted a field survey on the relationship between Fv/Fm and topographic wetness index (TWI) in seedlings of Japanese white birch and E. glehnii (closely related to E. makinoi) naturally grown in a study site 5 years after canopy tree cutting. Lower Fv/Fm was observed in seedlings of Japanese white birch with increasing TWI, whereas no significant trend was observed in E. glehnii, in agreement with the glasshouse experiment. Thus, keeping soils not always humid might be favorable to photosynthetic performance and growth competitive ability of Japanese white birch against Eupatorium species.

Exposure to strong irradiance exacerbates photoinhibition and suppresses N resorption during leaf senescence in shade-grown seedlings of fullmoon maple (Acer japonicum)

“…However, the extent of photoinhibition in LH3 seedlings was limited on 19 th Oct because of the shorter period (1 day) of exposure to open radiation. Although the degree of photoinhibition seems to be dependent on solar radiation and air temperature as well as the timing of simulated leaf shedding ( 2018a ; 2022 ; Werner et al., 2001 ; Kitao et al., 2004 ), severer photoinhibition, as was observed in LH2, might increase the risk of incomplete N resorption by oxidative damage.…”

Root-Zone Heat Priming Effects on Maximum Quantum Efficiency of PSII, Productivity, Root Morphology and Nutritional Quality of Two Aeroponically Grown Leafy Greens in a Tropical Greenhouse

“…However, all plants had similar predawn F v /F m ratios which were greater than 0.8 (data not shown). This finding suggests that all plants had fully recovered overnight and that no chronic photoinhibition occurred in any plants during RZ heat priming [30,31].…”

“…This result shows that when both temperate vegetable crops were subjected to 38 • C-RZT during midday, dynamic photoinhibition had occurred due to the midday's higher photosynthetic photon flux density (PPFD) and high leaf temperature in conjunction with the high RZT [17]. Dynamic photoinhibition in Canasta leaves during RZ heat priming leading to a decline in overall photosynthetic performance [17,[29][30][31] could have resulted in its significantly lower leaf area expansion than 25 • C-RZT Canasta leaves (Figure 1D). The impact of RZ heat priming on leaf growth may be species-dependent since there was no statistical difference in the leaf area expansion of Arugula leaves (Figure 1C) despite its significantly lower midday F v /F m ratio (Figure 1A).…”

Effects of Seedling Size, Stock Type, and Mechanical Site Preparation Method on Initial Survival and Growth of Japanese Larch (Larix kaempferi) Seedlings

“…Japanese larch has low shade tolerance and is therefore susceptible to significant loss of survival and growth, due to competition from surrounding vegetation [14,20]. Meanwhile, the vegetation growth is also influenced by site environmental conditions [21]. The influence of environmental conditions and vegetation growth on seedling performance must be considered when evaluating seedling quality based on the survival and growth in planting trials.…”