According to Carrie Huffman Wohleb, Associate Professor and Regional Specialist â€“ Potato, Vegetable, and Seed Crops at Washington State University, physiological age is an important concept in potato production.
“The physiological age of seed tubers determines when the buds will sprout and how many sprouts will develop from those buds,” she says. “It affects stem numbers and vine growth. It also influences tuber development and can have a significant impact on tuber yield and size distribution.”
What is physiological age? Physiological age differs from chronological age, Prof Wohleb says. “Chronological age is the number of days since the tuber was formed. Physiological age refers to the internal age of a tuber as it is affected by biochemical changes within.”
Like chronological age, physiological age advances with time. But itâ€™s also affected by genetics (e.g.., cultivar traits) and environmental stresses.
The same concepts are used to understand aging in humans, Prof Wohleb points out. “Some people seem much younger â€” or older â€” than they really are. Genetics are largely responsible for how we age, but lifestyle choices can have an important impact too.”
She says stress accelerates aging in potato seed tubers. “Plants respire to release the energy they need to keep cells functioning â€” starch and sugars are consumed to produce energy – itâ€™s basically the reverse of photosynthesis.”
When plants are stressed, they respire more. Any conditions that increase respiration rates will accelerate the aging process in tubers. This includes temperature extremes, moisture stress, nutrient deficiencies, pest injury, and rough handling during harvest, according to Prof Wohleb.
“Stresses encountered at any time during the life of a tuber can speed up aging; but many studies have shown that growing conditions have a smaller effect on physiological age than post harvest conditions.”