Photosynthetic parameters of maize (Zea mays L.) inbred lines and F-1 hybrids: their different response to, and recovery from rapid or gradual onset of low-temperature stress

The activity of photosystems (PS) 1 and 2, together with the content and ratio of photosynthetic pigments, were measured in three inbred lines and two F-1 hybrids of maize (Zea mays L.), grown in either optimum or low temperature (LT) conditions. The ability of chilling-stressed plants to deal with the negative effects of long-term exposure to LT and to recover the efficiency of photosynthetic apparatus after their return to optimum temperatures was examined during spring and autumn seasons. The aim was to analyse the possible differences between the rapid and gradual onset of LT on the response of young maize plants to chilling stress. The distinctive superiority of hybrids over their parental lines, found during the exposure of maize plants to LT, was not always retained after the return of chilling-stressed plants to optimum growth conditions. The response of individual genotypes to chilling stress, as well as their ability to recover the photosynthetic efficiency from the cold-induced damage, strongly depended also on the duration and the rapidity of the onset of LT.