2017 ASHS Annual Conference

Potatoes are known to grow well in cool climates. Heat stress generally reduces foliage growth and partitioning to tubers. Our previous studies have shown that heat stress reduces leaf size by reducing cell division and cell enlargement. Most studies to date have documented the adverse impact of heat stress on potato plant growth and development. However, very little has been reported on long-term adaptation of potato plants to heat stress. The present study was conducted to study strategies employed by potato plants to adapt to heat stress using five different commercially available cultivars. Shoot culture plantlets were grown in about 8 L pots containing an artificial soil mix (Metro Mix) in a temperature controlled greenhouse at the UW-Madison Biotron controlled environment facility under a 14-hour photoperiod. Six weeks after growing in cool (20⁰C/ 15⁰C, day/night) temperatures plants were transferred to a controlled environment room at the Biotron facility with similar light intensity and photoperiod but elevated temperature for heat stress treatment (35⁰C/ 25⁰C, day/night). After 5 weeks of heat stress exposure the new leaves developed under heat stress were compared with similar age leaves on control plants produced under control/ cool temperatures. The new leaves produced under heat stress were much smaller but very healthy and dark green. The leaves developed under control condition turned yellow and eventually necrotic under prolonged heat stress. In contrast the leaves developed under heat stress showed no symptoms of injury by heat stress. These heat stress adapted leaves had (i) dramatic increase in stomatal index, stomatal density, and cell density (ii) altered ground cell and stomatal complex size (iii) over 2x increase in leaf chlorophyll concentration per unit area. These results suggest that leaves developed under prolonged heat stress have altered cell differentiation and chlorophyll which may help plant adapt to heat stress and survive prolonged heat stress.