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Seedling morphology of Helianthus annuus var. US 666 is described. Seedlings were phanerocotylar-epigeal-reserve type. Hypocotyl grew rapidly bringing cotyledons aboveground while enclosed in pericarpic shell. The primary leaves showed brochidodromous venation. Leaves were wide elliptical with apex acute and often mucronate, dorsiventral and yellow green ventrally. The photosynthetic area (PA) of seedlings increased with age in quadratic manner as follows: PA (mm2 ) = - 9.2066 (Age in days) 2 + 348.88 (Age in days) – 983.55; R 2 = 0.8974. The leaves were simple, opposite, petiolate. Cotyledons were atrichomatous and leaves exhibited three types of trichomes, 1) Glandular moniliform multicellular uniseriate trichomes (GTs), 2) Glandular short-stalked capitate trichomes (CGTs) and 3) Non-glandular apically pointed trichomes (NGTs) of variable sizes. NGTs from mature leaf had reticulate epicuticular ornamentation with spike like projections, particularly on the lower cell. Cotyledonary epidermal cells were straight to slightly curve in anticlinal contour but wavy in leaves. The foliar pavement epidermal cells were quite intricate in shape with U-shaped undulations fitting like the pieces of the Jigsaw puzzle. The waviness varied substantially, (1- ) 2-12 (-13) crests per cell and averaged around six and varied on dorsal and ventral surfaces of primary and secondary leaves by 30.15 to 39.0%, respectively. Waviness was found not to vary significantly between dorsal and ventral surfaces of primary leaf. In the pooled samples, dorsal surface showed waviness 6.01 ± 1.02 crests per cell and ventral surface had waviness averaged to 6.05 ± 0.130 crests per cell. If viewed according to Prabhakar (2004), four types of stomata were observed in the laminar islands of leaf – tetracytic, anisocytic anomocytic and staurocytic on dorsal and ventral surfaces of primary, secondary, or tertiary leaves. Cotyledons were more diverse in stomata - Anomocytic, tetracytic, anisocytic, staurocytic, isotricytic, paracytic, and diacytic stomata were recorded. Often paracytic stomata changing to isotricytic or anisocytic were also observed. Clustering of stomata was often seen, and contiguousness of stomata was common. Stomata have been described for their density and relative abundance on the surface of various organs. According to the classical schemes of stomatal classification, stomata of in-hand sunflower variety were just of one kind, anomocytic stomata, being abutted with indistinct neighbouring cells. Classical schemes of stomatal classification appear to be more suitable from ontogenic viewpoint. Stomatal size in terms of length (L) and breadth (B) have been described. In 72.8% cases of stomata the L / B ratio fell within a class of 1.26 to 1.75.
D. KHAN, M. JAVED ZAKI. (2020) MORPHOLOGICAL CHARACTERISTICS OF SEEDLINGS OF SUNFLOWER (HELIANTHUS ANNUUS VAR. US 666), , Volume 17, Issue 3.
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