Carbohydrate export from the leaf: a highly regulated process and target to enhance photosynthesis and productivity

OverviewOxygenic photosynthesis plays a central role in the global carbon and oxygen cycles. The carbohydrates produced support nearly all food webs, while the oxygen by‑product enables aerobic life.Light‑dependent and light‑independent reactionsPhotosynthesis occurs in two main stages, each in a different part of the chloroplast: light‑dependent reactions and light‑independent reactions, also called the Calvin‑Benson cycle or simply the Calvin cycle.Light‑dependent reactions take place in the...

Ribulose 1,5- bisphosphate carboxylase/oxygenase (RuBisCo) is a critical enzyme that catalyzes carbon dioxide assimilation during photosynthesis. However, it is an inefficient enzyme, having an extremely slow catalytic rate. A typical enzyme can process about a thousand molecules per second; however, RuBisCo fixes only around three-carbon dioxides per second. Photosynthetic cells compensate for this slow rate by synthesizing very high amounts of RuBisCo, making it the most abundant single...

Most plants use the C3 pathway for carbon fixation. However, some plants, such as sugar cane, corn, and cacti that grow in hot conditions, use alternative pathways to fix carbon and conserve energy loss due to photorespiration. Photorespiration is the process that occurs when the oxygen concentration is high. Under such conditions, the rubisco enzyme in the Calvin cycle binds O2 instead of CO2, which halts photosynthesis and consumes energy.
C4 Pathway
The C4 pathway is used by plants such as...

Like many living organisms, plants have tissues that specialize in specific plant functions. For example, shoots are well adapted to rapid growth, while roots are structured to acquire resources efficiently. However, sugar production is primarily restricted to the photosynthetic cells that reside in the leaves of angiosperm plants. Sugar and other resources are transported from photosynthetic tissues to other specialized tissues by a process called translocation.

Photosynthesis is a multipart, biochemical process that occurs in plants as well as in some bacteria. It captures carbon dioxide and solar energy to produce glucose. Glucose stores chemical energy in the form of carbohydrates. The overall biochemical formula of photosynthesis is 6 CO2 + 6 H2O + Light energy → C6H12O6 + 6 O2. Photosynthesis releases oxygen into the atmosphere and is largely responsible for maintaining the Earth’s atmospheric oxygen content.

All living organisms on Earth are directly or indirectly dependent on photosynthesis. It is the only biological process that can capture energy from sunlight and convert it into chemical energy that every organism can use to power its metabolism. Photosynthesis is also the source of oxygen required by many living organisms.
Types of Organisms Based on their Modes of Nutrition
Broadly, there are two main categories of organisms based on their modes of nutrition — autotrophs and heterotrophs. An...