Daytime gas exchange in soybean plants submitted to waterlogging and shading

ABSTRACT: Aerobic respiration declines in the root tissue of soybean plants exposed to waterlogged soil with a low oxygen content, causing metabolic disorders that negatively affect gas exchange and photosynthetic activity, hampering growth and production. As such, this study to investigated daytime gas exchange, relative chlorophyll content, specific leaf area (SLA) and photosynthetic activity curves in response to photosynthetic photon flux density (PPFD) in soybean plants grown under different conditions: no stress (control), shading, waterlogged soil, and waterlogged soil + shading. Soybean plants exposed to either waterlogging or shading and both conditions simultaneously exhibited reduced photosynthesis linked to lower stomatal opening. Plants submitted to shading showed an increase in SLA, quantum yield and photosynthetic rates, while those grown in waterlogged soil, in full sun, exhibited chlorotic leaves and low apparent quantum yield, resulting in low photosynthetic rates under shading and high light levels. Thus, waterlogging and shading in isolation or combined, compromise daytime gas exchange and alter photosynthetic activity in plants.