Open Access

ARTICLE

Leaf Position on the Sunflower Stem Determines Physiological Condition during Flowering

Antonela Markulj Kulundžić^1,*, Daniela Horvat², Marija Kovačević Babić², Anto Mijić¹, Aleksandra Sudarić¹, Maja Matoša Kočar¹, Tomislav Duvnjak¹, Ivica Liović¹, Ivana Varga³, Marija Viljevac Vuletić^2,*

1 Department of Industrial Plants Breeding and Genetics, Agricultural Institute Osijek, Osijek, 31000, Croatia
2 Agrochemical Laboratory, Agricultural Institute Osijek, Osijek, 31000, Croatia
3 Faculty of Agrobiotechnical Sciences Osijek, J.J. Strossmayer University of Osijek, Osijek, 31000, Croatia

* Corresponding Authors: Antonela Markulj Kulundžić. Email: ; Marija Viljevac Vuletić. Email:

(This article belongs to the Special Issue: Influence of Biotic and Abiotic Stresses Signals on Plants and their Performance at Different Environments)

Phyton-International Journal of Experimental Botany 2025, 94(7), 2075-2095. https://doi.org/10.32604/phyton.2025.065961

Received 26 March 2025; Accepted 19 June 2025; Issue published 31 July 2025

Abstract

Sunflower leaf photosynthesis strongly depends on the leaf position in the plant stem conditioning, which directly affects other physiological processes. Therefore, a study of the leaf’s physiological status regarding the leaf position in the stem was performed on sunflowers in the flowering stage. Eight differently positioned leaves were investigated, starting with the youngest leaf on the top of the stem to the leaves of the stem bottom, assigned as the oldest senescent leaves. According to chlorophyll fluorescence (ChlF) parameters connected to photosystem II (PSII) processes, significant changes in PSII functioning occurred only in the senescent leaves, while photosystem I (PSI) describing parameters showed a linear decrease with leaf age, i.e., position on the stem. The antioxidative status of the leaves was dynamic, as stress indicators (lipid peroxidation and hydrogen peroxide content) fluctuated regarding leaf position on the stem, but no link was found between the activities of antioxidative enzymes and oxidative stress indicators. Linear decrease trend of secondary metabolites (mainly phenolic compounds) correlated with antioxidant activity, except for some phenolic acids (caffeic and ferulic acid), which increased in senescent leaves. The most changes in the physiological status of the leaves were confirmed in senescent leaves, which stand out the importance of younger leaves in maintaining the plant’s vitality after flowering, which is the most important for sunflower yield.

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Keywords

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