Influenţa epocii de semănat asupra biologiei aparatului foliar la unii hibrizi de floarea soarelui cultivaţi în Câmpia Moldovei

Abstract

Our investigations have followed the influence of sowing period on the biology of leaf apparatus in sunflower by determinations on the shape, structure and activity of photosynthetic apparatus. The trials were conducted on five sunflower hybrids (P.I. 2001, Select, P.I. 2002, P.I. 2004 and Performer), sown in two periods: the first period on April 16, 2007 and the second period on May 2, 2007, under conditions of the Moldavian Plain. The leaf morphogenesis was analysed by determining the number of active leaves/plant, their sizes (length/width) and the leaf area/plant, as well as by establishing the leaf anatomical structure at limb and petiole level. The results obtained have demonstrated that the leaf morphogenesis was differentiated according to studied hybrids and sowing period. The investigations concerning the leaf anatomical structure showed differences between variants at the level of stomata apparatus and guiding tissue. The differences are quantitatively: number of collenchymas layers, number of stomata per area unit, number of guiding beams, and qualitatively: presence of concentric beams, presence of lignified cell cap in the phloem parenchyma and of the two stomata types.