The magnitude of transpiration is impressive. A 48-foot (16-m) silver maple tree is estimated to transpire as much as 58 gallons (220 L) per hour. A forest of temperate-zone, broad-leaved trees transpires about 8000 gallons (30,000 L) of water per acre per day. An average-size tomato plant transpires about 30 gallons (115 L) during its growing season; a corn plant, 55 gallons (210 L). Such quantities represent the plants’ basic needs to be supplied via the soil by rain and irrigation.
