The main photosynthetic organ of a plant where light energy is converted to chemical energy (food) through photosynthesis, also respiring and transpiring water.
In plain terms
Leaves are the plant's food factories. Sunlight hits the leaf, chlorophyll absorbs the energy, and the plant manufactures food. Leaves also release water vapor (transpiration) and exchange gases. Damaged, diseased, or insufficient leaves slow photosynthesis, weakening the plant. Yellow or pale leaves signal problems: nutrient deficiency, disease, or insufficient light.
Why this matters
Leaves are where plant productivity happens. Problems with leaves (yellowing, spotting, damage) mean reduced growth and yields.
In practice
Examples
Healthy green leaves; photosynthesis proceeding efficiently; plant grows strong.
Yellowing leaves signal nitrogen deficiency; nitrogen fertilizer returns color and growth.