Capturing the light Modern practices have improved the
partitioning of dry matter into fruit, but light capture is well
below the biological limit, a New Zealand horticulturist says.
John Palmer is with the New Zealand Institute for Plant and Food
Research. If apple growers could capture all the sunlight energy
that falls on their orchards and convert it into salable fruit,
they could sell more than 20,000 bushels per acre each year,
instead of about 700. Less than one percent of the sun’s visible
light energy striking an orchard is captured in fruit. That
leads John Palmer to say: “I do not believe we have reached the
limit of the biological system.” Still, Palmer thinks great
progress has been made in apples in recent years. He came into
the world of scientific research as a tree fruit physiologist in
1968, when most trees were still big producers of wood. The
measure of how much fruit a tree produces from all of the dry
matter it accumulates is known as the harvest index. In the
past, the harvest index was