Photosynthetic properties of erect leaf maize inbred lines as the efficient photo-model in breeding and seed production

Abstract

The initial idea of this study was a hypothesis that erect leaf maize inbred lines were characterized by properties of an efficient photo-model and that as such were very desirable in increasing the number of plants per area unit (plant density) in the process of contemporary selection and seed production. The application of a non-invasive bioluminescence-photosynthetic method, suitable for the efficiency estimation of the photo-model, verified the hypothesis. Obtained photosynthetic properties of observed erect leaf maize inbred lines were based on the effects and characteristics of thermal processes of delayed chlorophyll fluorescence occurring in their thylakoid membranes. The temperature dependence of the delayed chlorophyll fluorescence intensity phase transitions (critical temperatures) in the thylakoid membranes and activation energy are the principal parameters of the thermal processes. Based on obtained photosynthetic properties it is possible to select erect leaf maize inbred lines that are resistant and tolerant to high and very high temperatures, as well as, to drought. They could be good and efficient photo-models wherewith

Quality traits of maize inbred lines and hybrids with efficient photosynthetic functions

“…Measures of the angle between the above-ear leaf and the stalk and of the leaf areas were carried out on 218 plants for each inbred line during the three-year period. These methodical procedures were described in previously published papers [18].…”

“…In addition, a programme on the development of maize inbred lines with erect top leaves was established at the same time as the «plant density» programme. It was considered that inbreds with the erect top leaves were the closest to the proposed efficient photosynthetic model [18,21]. The complementary and mass implementation of these programmes led to very important results in both, maize breeding and the hybrid seed production.…”

“…The results obtained on these traits (Tab. 1) classify them into important breeding and seed production traits [18,19]. The second series of experiments encompassed photosynthetic fluorescence studies on conformational and functional changes in chloroplasts and the thylakoid membranes of the intact above-ear leaf of new maize inbred lines.…”

“…All critical temperatures (phase transition temperatures) at which even the slightest conformational changes had occurred in the thylakoid membranes of new maize inbred lines with erect top leaves were determined by the Arrhenius criterion and the linearization of the DF temperature dependence. The values of critical temperatures in °C, their frequency and intermediate distance characterise observed maize inbred lines with erect top leaves in relation to their tolerance, resistance, flexibility and adaptability not only to increased and high temperatures, but also to drought [18].…”

“…Since 1978, the number of plants per area unit (plant density) has been significantly increased, which mostly affected the increase in grain yields [20]. At the same time, a programme of breeding and seed production of maize hybrids that included inbreds with erect top leaves has been performed [6,18]. Maize plants architecture is a major contributing factor to their high level of productivity [26].…”