Blanketflower (Gaillardia pulchella Foug.) is a tall herbaceous annual (more than 1 m long), usually subjects to slanting if it was grow alone in pot. So, the present investigation was carried out at Orman Botanical Garden, Giza, Egypt during the seasons of 2012/2013 and 2013/2014 in order to reduce its tall and branched stem by spraying the foliage with the aqueous solution of either paclobutrazol (PP-333) at 0, 50 and 100 ppm or cycocel (CCC) at 0, 1000 and 2000 ppm concentrations, two times with 3 weeks interval, and to study the effect of these treatments on flowering and chemical composition of 75-days-old seedlings of such winter annual when grown in 15-cm-diameter plastic pots filled with about 1.5kg of an equal mixture of sand and clay (1:1, v/v).
The obtained results indicated that both PP-333 and CCC at various concentrations significantly decreased all vegetative and root growth criteria, with few exceptions compared to control in the two seasons. The low level of PP-333 caused about 20% reduction in height and branching of treated plants giving plants near at its size to those of control ones. On the contrary, the high level of CCC (2000 ppm) excessively decreased these parameters to more than 65% compared to control treatment, and that was accompanied with reducing root length to less than 10 cm in both seasons. However, the most appropriate size wherefrom height, branching and number of leaves was gained from applying either PP-333 at 100 ppm or CCC at 1000 ppm, with the preference 100 ppm PP-333 treatment which resulted the most suitable plant size in harmony with the pot size.
The flowering was delayed due to all the used treatments, but delaying by CCC treatments was more than that by PP-333 ones (about 7-9 days against only 4-5 days, respectively). All other flowering characters were significantly decreased by the different levels of growth retardants used in this work in most cases of both seasons, except for the two rates of PP-333 which were raised inflorescence diameter and number of ray florets/inflorescence, with the superiority of PP-333 at 100 ppm treatment, as it gave the widest inflorescence with the utmost high number of ray florets per inflorescence at all. This treatment also resulted the shortest stalk length which was useful in restricting flower head nutation phenomenon in this plant. Paclobutrazol at any rate markedly increased chlorophyll a and b, carotenoids, total soluble sugars, total indoles and total phenols content in the leaves, whereas CCC treatments decreased content of these constituents with the exception of total phenols content that was greatly increased.
From the previous results, it is recommended to spray the foliage of 75-days-old seedlings of Gaillardia pulchella winter annual plant with PP-333 at 100 ppm level, twice with 3 weeks interval for production of petit, dwarfed, flowering-pot-plant from commercial point of view.