Wpływ następczy temperatur chłodowych w termoperiodyzmie dobowym na produktywność fotosyntetyczną kukurydzy (Zea mays L.)
AbstractThe effect of 24-h thermoperiods with chill nights on the productivity of maize was investigated in experimental arrangements in which the range and the time of exposure to the temperature at night was varied, the temperature of the aboveground part of the plants and of the roots as well as the vegetation conditions during the day were differentiated. It has been found that the chilling temperatures at night reduce the photosynthesis intensity in the seedlings not only during the immediate day but during a number of subsequent days. In both cases the inhibition of rate of the process of photosynthesis increases with the number of chill nights and lowered temperature. The change in the rate of the process of photosynthesis as a reaction to lowered temperature at night is revealed only in favourable conditions of temperature and irradiation of plants. The inhibition of photosynthesis under unfavourable measurement conditions masks the aftereffects of the influence of night chilling temperatures. Lowered temperature during the day (2oC) after chill nights enhances the inhibition of the process of photosynthesis much more than only the night exposure to chilling temperatures. This effect increases with the periods of exposure to chill during the day. The cause of the strong inhibition of the photosynthesis process after prolonged chill at day and night are deep metabolic changes manifested as the damage of the leaves tissues. An illustration of the great sensitivity of the process of photosynthesis to a thermal stress is its inhibition after a short period of exposure to chill at night which becomes revealed without any visual damage of the leaves. The decrease in the intensity of photosynthesis after exposure to chill in darkness i.e connected with reduced diffusion of CO2 by the stomatal apparatus which does not open completely, with disturbances of the water management of the seedlings as well as with low concentration of the "a+b" chlorophyll in the leaves, below 50 mg per 1 cm2. The development and the increase of the surface area of the leaves after 10 nights with the temperature 5o and 12oC acting on the plant at the phase of seedling is limited subsequently through the greater part of the vegetation period. The above mentioned conditions, however, do not determine the ultimate surface area of assimilation. The rate of the increase of the surface area of the leaves of seedlings is more inhibited by the lowered temperature of the soil at night than by air temperature. The effect of the night chilling temperature 5°C on the increase in the biomass depends on the development phase of the plants. The influence of chill for 10 successive nights on 10 day old plants is disadvantageous, in 42 day old plants it does not produce any visible reaction, while in 92 day old plants the influence is even advantageous. Reduction of the increase rate of the seedlings biomass after completion of chilling at night is approximately directly proportional to the number of chill nights. Chilling temperatures affecting the roots inhibit much more the increase of the seedlings biomass than the chilling temperatures affecting the aboveground part of the plants. Particularly disadvantageous for the increase of the biomass of seedlings at the temperature 5°C is keeping the roots in chill for the whole 24-h periods, as it leads to a damage of the roots system. Lowered temperature to 5°C of the whole seedlings during one night is enough to induce the aftereffect of reducing the rate of the process of the translocation of assimilates from the leaves to the roots at higher temperatures. The chilling temperature 5°C tends to increase the dissimilation losses of assimilates accumulated in the plants. This effect is associated with reduced photosynthetic reassimilation of CO2, prolonged period of export of assimilates fez the leaves and retaining some part of assimilates in the leaves. Ten cycles of 10 days, 12 h long, applied starting with the 10th, 42nd and 92nd day of vegetation results in a differentiation of the development reactions of the plants. When employed starting with the 10th day, it accelerates the generative development and shortens the length of the vegetation period with respect to the cycles acting in the later growth periods. Night chilling temperatures (5° and 12°C) operating within a period from 10 to 20 days after the plants germination may as an aftereffect prolong the period of filling the assimilates with seeds and increase the fraction of grains in the biomass of the aboveground parts of the plants.
|Other language title versions||AFTEREFFECT OF CHILLING TEMPERATURES IN THE 24-h THERMOPERIODS ON THE PHOTOSYNTHETIC PRODUCTIVITY OF MAIZE (Zee mays L.)|
|Publisher||Uniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie, MNiSW |
|Publishing place (Publisher address)||Kraków|
|Book series /Journal (in case of Journal special issue)||Zeszyty Naukowe Akademii Rolniczej im. H. Kołłątaja w Krakowie. Rozprawy, ISSN 1233-4189, (0 pkt)|
|Publication size in sheets||4.5|
|Citation count*||8 (2016-07-03)|
* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.