Which condition limits photosynthetic rate when rubisco enzyme concentration in leaf cells remains constant?

💡 Explanation

When rubisco is constant, photosynthetic rate limiting factor shifts to substrates; decreasing CO2 diffusion reduces substrate availability because rubisco's carboxylation activity becomes limited despite sufficient enzyme levels. Therefore reduced CO2 diffusion limits photosynthesis rate, rather than water availability, nutrient uptake, or respiration which affect different processes.

• Which mechanism assists soaring birds in compensating against increased wing loading induced by added mass, for instance rainwater accumulating in plumage?
• Which risk increases when a soaring bird encounters a turbulent atmospheric layer with decreased coefficient of lift?
• Which outcome reduces the upward water movement when tension exceeds the root's capacity to supply water in a tall tree?
• Which outcome predictably occurs when avian flight feathers experience excessive bending during high-speed flight?
• Which outcome occurs when marine mammals dive deeply, causing alveolar collapse?
• Which biomechanical effect underlies efficient oxygen extraction from air sacs during avian flight?