Morphological, Anatomical, and Physiological Adaptations of Potatoes to a Simulated Heat Stress

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 the adaptation of potato plants to heat stress. The present study was conducted to study strategies employed by potato plants to acclimate 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 University of Wisconsin, Madison Biotron controlled environment facility using a 14 hour photoperiod. Six weeks after growing in cool (20 °C day/ 15 °C night) temperatures plants were transferred to a controlled environment room at the Biotron facility for heat stress treatment (35 °C day/ 25 °C night) under a 14 hour photoperiod. After 4–5 weeks after heat stress exposure, the leaves produced under heat stress were compared with the leaves on the same plants that were produced under cool temperatures prior to heat stress. In general as expected the leaves produced under heat stress were smaller. Heat stress adapted leaves had (i) dramatic increase in stomatal index and stomatal density, (ii) thicker and highly developed palisade cell layer, and  (iii) over 2x increase in chlorophyll per leaf area. Infra-red leaf temperature measurements showed that heat stress adapted leaves maintained cooler leaf temperatures. These adaptations appear to help plants mitigate heat stress effects.