2g - Plant Gas Exchange

Air Spaces

细胞间隙 (叶肉中) (xìbāo jiànxì (yèròu zhōng de)) / 气室 (qìshì) Interconnected spaces between spongy mesophyll cells within a leaf that allow for efficient diffusion of gases (like CO₂ and O₂) to and from photosynthesizing cells.

Compensation Point

补偿点 (bǔcháng diǎn) The point (e.g., specific light intensity) where the rate of photosynthesis equals the rate of respiration in a plant, resulting in no net exchange of oxygen or carbon dioxide.

Diffusion Gradient

气体扩散梯度 (qìtǐ kuòsàn tīdù) The difference in concentration of a gas (e.g., CO₂, O₂) between two areas (e.g., inside and outside the leaf), which drives the movement of the gas from high to low concentration.

Guard Cells

保卫细胞 (bǎowèi xìbāo) Pairs of specialized cells surrounding each stoma; they control the opening and closing of the pore, thus regulating gas exchange and water loss.

Hydrogencarbonate Indicator

碳酸氢盐指示剂 (tànsuānqīngyán zhǐshìjì) A chemical solution that changes color in response to CO₂ concentration, used to investigate gas exchange (e.g., photosynthesis and respiration) in aquatic plants or enclosed systems.

Net Gas Exchange

净气体交换 (jìng qìtǐ jiāohuàn) The overall difference between the amount of a specific gas taken in by a plant and the amount released over a period (e.g., net CO₂ uptake during the day).

Spongy Mesophyll Layer

海绵状叶肉层 (hǎimiánzhuàng yèròu céng) The layer of loosely packed cells within a leaf, below the palisade layer, with many air spaces providing a large internal surface area for gas exchange.

Stomata (singular: Stoma)

气孔 (qìkǒng) Tiny pores, mainly on the lower surface of a leaf, formed by guard cells, which allow gases (CO₂, O₂, water vapour) to diffuse into and out of the leaf.