A Matter of Taste - Soil: Reflections on the Basis of our Existence - page 114

Creative evolution . Plants are biochemical factories, their leaves full of green chlorophyll that
captures light in the process of photosynthesis. They also contain many other pigments. The red
anthocyanins, seen in autumn leaves after the chlorophyll has been broken down, protect the cells
from the sun's ultraviolet rays. When plants come under attack from pests they produce protective
substances that the invaders try to circumvent, in turn causing plants to evolve new defences in a
constantly escalating arms race. The maple leaf in the photo is suffering from tar spot
longer molecules that create a softer taste because they do not penetrate the small-
est mouth cavities. By attaching themselves to proteins, tannins make themselves
harder to absorb for insects and other creatures that eat the plant. This is a shrewd
tactic because the tannin content in grape skin is highest when the grapes have grown
large in size but the seeds are yet to ripen, while tannin content drops as the grapes
ripen and their sugar content rises. It is at this point that the grapes become palatable
to birds, which help to disperse the seeds. Winemakers can influence the presence of
taste-stimulating substances by removing leaves that overshadow the grapes, expos-
ing them to more ultraviolet light, and by timing the harvest correctly.
Growing conditions also play a central role in how a wine develops. Excessive
overwatering and soil nitrogen result in vines growing more leaves and fewer
grapes. Many winemakers will tell you that it is vital to limit watering during
the maturation process to ensure good quality grapes that are smaller in size with
thicker, tannin-rich skins. A lower harvest volume often results in higher-quality
wine, while nutrient-rich conditions and moist soil produce a higher grape volume