Peas are in the dark inside a pod, so can鈥檛 use their chlorophyll for photosynthesis. In which case, why are they green?
Jo Murphy
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Waikanae, New Zealand
Peas aren鈥檛 鈥渋n the dark鈥� because light penetrates almost all vegetation during daylight hours.
Roy Smith
Burntwood, Staffordshire, UK
Pea pods are translucent even when mature. I often look through the pods of the peas I grow, to see when they are ready to harvest. Even when mature, some light gets through the pod wall.
Think about shrubs in a forest 鈥� they get much less light than the treetops, but still enough to photosynthesise and even their lowest leaves are green. Likewise for peas in a pod.
Peter Jackman
Llandysul, Ceredigion, UK
Pea seeds naturally appear in a variety of colours from shades of yellow to dark purples, but it is the vibrant green pea that has been exploited widely for food and considered desirable. Selective breeding has been used to achieve this desired visual appearance.
Chlorophyll is broken down by proteins encoded by so-called stay-green genes, and the decline of chlorophyll levels causes yellowing of the peas.
Many plants that we eat have been selected for mutations in these genes, which thus cause retention of greenness.
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