EFFECTS OF HYPOTHERMIC STRESS APPLIED TO SEEDS BEFORE GERMINATION ON THE PARAMETERS OF THE PHOTOSYNTHETIC APPARATUS OF MAIZE PLANTS

Rezumat

In maize (Zea mays L.) plants grown from seeds pre-treated with negative temperature stress (NTS) of -4°C for 16 hours before germination, followed by growth in dark and light conditions, the content of chlorophyll pigments (Chl) in leaves, the chlorophyll content index (CCI) and some gas exchange parameters were assessed. Combined application of NTS and illumination conditions to seedling growth showed that 6-day-old NTS maize seedlings grown in the dark were etiolated, contained carotenoids and traces of Chl a and Chl b. Whereas in green seedlings grown in the light, NTS decreased Chl a, Chl b and carotenoids. NTS also reduced the CCI in1st, 2nd and 3ed leaves of plants grown in the light for 17 days. While in the 1st, 2nd and 3ed leaves of control plants that grew in the light, the CCI changed dynamically, showing a maximum on the 9th day of growth and then decreased. The influence of NTS also affected the parameters of gas exchange in leaves, causing a decrease in CO2 exchange, real CO2 absorption and total respiration.