IRKUTSK, RUSSIA
Institute of Plant Physiology and Biochemistry

Growth of maize primary roots under long-term impact of low temperature

— Akimova, GP; Sokolova, MG; Nechaeva, LV

The work was focused on the growth of primary maize sprouts under long-term impact of low positive temperature at early stages of ontogenesis.

The tests were conducted on 48-hours-old plants (MNL 76: 35–36, 2002). In the laboratory conditions we determined the speed of growth of maize sprouts primary roots under long-term impact of the temperature 10°C (10 days), as well as restoration of the growth at 27°C (MNL 71:93, 1997).

The following maize hybrids and varieties were used for the tests: Zherebkovsky 86, Kollektivny 224, Dneprovsky 320, Odessky 80, VIR 42, Bekke LLO, Bukovinsky 3, Omskaya 2. Uzbekskaya tooth-like variety characterized by late ripening and sensitivity to low temperature impact was used as a classifying variety.

Under long-term impact of low temperature, maize varieties and hybrids under investigation significantly slowed down the root growth speed, which on average equaled 0.04 mm/hour and amounted to 55–60% of the initial root growth speed at temperature 10°C (Table 1). Only Omskaya 2 variety and Kollektivny 244 hybrid showed root growth speed equaling 0.10 mm/hour.

At 10°C the cells took longer to reach their final dimensions. It should be noted that unlike short-term impact of low temperature, in this case the cells both started and terminated extension under 10°C. The cells of Uzbekskaya tooth-like sprouts roots, which started extension at 10°C, did not reach their final dimensions during the test time (10 days). The zone length considerably exceeded (doubled) the zone length of other maize sprouts.

Restoration of the root growth speed after long-term impact of the temperature 10°C was observed for 24 hours. 6 hours after the return to the temperature 27°C, the root growth speed restoration reached 15–20% of control in the Uzbekskaya tooth-like variety, Bekke LLO, VIR 42 and Zherebkovsky 86 hybrid. Omskaya 2 and Kollektivny 244 showed a much higher percentage of the root growth speed restoration. 24 hours after the root growth speed more than doubled and reached 80–85% of the root growth speed of the sprouts, which were not subjected to the low temperature impact, Omskaya 2 variety and Kolektivny 244 hybrid and 35–63% of other maize hybrids.

Thus, long-term impact of the temperature 10°C allowed to identify differences in the response of maize varieties and hybrids under study. Low-temperature-resistant maize plants are characterized by accelerated cells differentiation type conditioned by their adaptation to low temperature at early growth stages. Growth response of maize primary roots and sprouts to low temperature impacts differing in depth and duration is a reliable characteristic of the resistance degree of the varieties and hybrids under study, which are distributed in relation to the classifying variety – Uzbekskaya tooth-like, along with the resistance increase in the following way: Odessky 80, Dneprovsky 320, VIR 42, Bekke LLO, Zherebkovsky 86, Kollektivny 244, Omskaya 2.

Analysis of the data acquired shows that resistant maize varieties and hybrids reach hardened state during 2–3 days of cold impact, whereas sensitive varieties do not reach this state, which tells on the character of their growth under longer and deeper temperature impact.

Table 1. Maize root growth speed under long-term impact of 10°C

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