Seismic stress effects on vegetative and reproductive development of 'Alaska' pea

Vegetative and reproductive growth responses of pea (Pisum sativum L. cv. Alaska) to periodic seismic (shaking) stress were investigated during fall, winter, and spring seasons in a greenhouse. Growth changes caused by equivalent shaking treatment varied quantitatively among seasons, with the least response occurring during winter, but they were qualitatively similar during all three seasons. Shaking caused significant reduction in all growth parameters measured except root dry weight and leaf number after 16 days of treatment. Reproductive growth responses to shaking (occurring from 16 to 35 days of treatment) included delay of anthesis but no difference in number of fruits set after as much as 35 days of treatment. Seismic stress significantly reduced the number but not the weight of individual seeds per pod. Mean relative shoot growth rate was reduced by shaking during reproductive as well as vegetative growth. During both periods of development this response was caused almost entirely by inhibition of net carbon assimilation rate.