Interdependence between oscillations and transients of delayed fluorescence induction processes in the thylakoid membrane of the intact maize leaf: Responses to effects of increased temperatures and drought

Abstract

Standard induction processes of delayed fluorescence (DF) of chlorophyll (induction signals) occur when an intact leaf segment of maize inbreds and hybrids is kept in the phosphoroscope darkroom for more than 15 minutes (t > 15 min), and at the same time the leaf is illuminated with the intermittent white light. Resolved induction processes of DF chlorophyll into transients: A, B, C, D and E occur when the intact leaf segment of maize inbreds and hybrids is kept in the phosphoroscope darkroom for a significantly shorter period (500 s > t > 30 s), with the time rate t of 30 s, prior to its illumination with the intermittent white light. Induction transients: A, B, C, D and E are characterized with the time of their generation: tA = 31±6 ms (A), tB = 5 ± 0,5 s (B), tC = 15±5 s (C), tD = 360±20 s (D) and tE = 670±35 s (E), dynamics of changes in transients intensities (IA, IB, IC, ID and IE) and mechanisms of their generation. The induction processes of chlorophyll DF of the intact leaf of maize inbreds and hybrids resolved into transients: A, B, C, D and E are accompanied by the occurrence and different levels of activation energy (Ea, kJ mol-1) that correspond to critical temperatures ranging from 28 to 33°C. The generation mechanisms of induction transients A, B, C, D and E classify them into two groups. Transients A and B are of a physical character, while the transients: C, D, and E are of a chemical character. It is shown that the generation of the induction transients: B, C, D and E simultaneously follows establishing of the oscillations of induction processes of the DF chlorophyll. Oscillating of induction processes of DF chlorophyll is explained by the ion (K+, Na+, H+, Cl-) transport mechanism across the thylakoid membrane of the intact leaf of maize inbreds and hybrids grown under conditions of air drought, increased temperatures and water deficiency in the medium.

U ovom radu ostvaruje se primena poboljšanog fotosintetično-fluorescentnog metoda u proučavanju složenih indukcionih procesa zakasnele fluorescencije (ZF) hlorofila, koji su razloženi na tranzijente: A, B, C, D i E i kod kojih mogu da nastanu oscilacije. Međuzavisnost oscilacija i indukcionih tranzijenata: A, B, C, D i E javlja se kod intaktnih listova linija (ZPR 70ž i Oh 43) i hibrida (ZPDC 360, ZPSC 46A, ZPSC 704 i ZPSC 71) kukuruza koji su gajeni u staklari u uslovima različite vazdušne suše, delovanja viših temperatura i deficita vode u podlozi. Posebno se ukazuje na uslove pri kojima dolazi do uspostavljanja standardnih indukcionih procesa ZF hlorofila. Daje se kraći opis standardne indukcione krive ZF hlorofila. Znatno detaljnije daju se eksperimentalni rezultati o razlaganju indukcionih procesa ZF hlorofila na tranzijente: A, B, C, D i E. Pokazani su vremenski i fizičko-hemijski parametri za proučavane indukcione tranzijente. Objašnjeni su njihova priroda i mehanizmi nastajanja. Utvrđene su karakteristike i mehanizam nastajanja oscilacija indukcionih procesa ZF hlorofila. Dati su uslovi pri kojima dolazi do pojave pobuđenog stanja, nastajanja fluktuacija i uspostavljanja oscilacija indukcionih procesa ZF hlorofila u tilakoidnoj membrani intaktnog lista linija i hibrida kukuruza. Izneta je hipoteza o mehanizmu nastajanja oscilacija. Objašnjena je međuzavisnost uspostavljanja oscilacija i tranzijenata indukcionih procesa ZF hlorofila.