PHOTOSYNTHESIS IN TOBACCO (Nicotiana tabacum L.) LEAVES DEVELOPMENT

Abstract

Duhan (Nicotiana tabacum L.) je gospodarski značajna kultura, a ujedno i često korišteni modelni organizam u biološkim istraživanjima. U ovom radu cilj je bio istražiti dinamiku razvoja fotosintetskog aparata tijekom ontogeneze listova duhana određivanjem koncentracija fotosintetskih pigmenata ključnih za apsorpciju svjetlosti (Chl a, Chl b) i mjerenjem fluorescencije klorofila a u svrhu procjene funkcionalnosti fotosintetskog aparata. Početna mjerenja izvršena su na listovima 14 dana starih presadnica, a sljedeća su obuhvatila pet insercija odnosno pet parova listova starosti 20, 24, 29, 32 i 37 dana. Rezultati su pokazali konstantni porast maksimalnog kvantnog prinosa fotosustava II (TR0/ABS) i indeksa fotosintetske učinkovitosti (PIABS) tijekom razvoja, potvrđujući kompetentnost ispitivanih skupina listova za učinkovito apsorbiranje i iskorištavanje energije u fotokemijskim procesima, unatoč različitoj dinamici akumulacije fotosintetskih pigmenata (Chl a, Chl b, Chl a+b). Porast gustoće aktivnih reakcijskih središta (RC/CS0) i smanjenje apsorpcije (ABS/RC) osigurali su porast učinkovitosti fotosustava II tijekom razvoja listova. Najviše koncentracije pigmenata izmjerene u insercijama 2 i 3 ukazuju na maksimum eksponencijalnog rasta listova u toj fazi razvoja. Degradacija pigmenata u insercijama 4 i 5 nije utjecala na funkcionalnost fotosintetskog aparata što je utvrđeno visokim vrijednostima parametara TR0/ABS i PIABS, ali ipak ukazuje na početak senescencije listova.Tobacco (Nicotiana tabacum L.) is one of the most economically important crops and also frequently used model organism in biological researches. The aim of this study was to investigate the dynamics of photosynthetic apparatus development during tobacco leaf ontogenesis. The concentration of photosynthetic pigments crucial for light absorption (Chl a, Chl b) as well as chlorophyll a fluorescence were measured to estimate functionality of photosynthetic apparatus. The measurements were performed on 14-day-old transplants and five insertions (leaf pairs) differing in developing stage (20, 24, 29, 32 and 37 days old). The results showed a constant increase of maximum quantum yield of photosystem II (TR0/ABS) and performance index (PIABS) during development, confirming the competence of all studied leaves for efficient utilization of absorbed energy in photochemical processes, despite the different pattern of pigments accumulation. Increasing density of active reaction centers (RC/CS0) and decreasing absorption (ABS/RC) provided a high photosystem II efficiency in developing leaves. The highest pigment concentrations measured in insertions 2 and 3 indicate that maximum exponential growth has been reached at this stage. The pigments degradation observed in insertions 4 and 5 did not affect the functionality of the photosynthetic apparatus, confirmed by the high values of TR0/ABS and PIABS, but nevertheless suggested the onset of leaf senescence