Effects of different potting growing media for Petunia grandiflora and Nicotiana alata Link & Otto on photosynthetic capacity, leaf area, and flowering potential

RESEARCH Effects of different potting growing media for Petunia grandiflora and Nicotiana alata Link & Otto on photosynthetic capacity, leaf area, and flowering potential Gheorghe Cristian Popescu1*, and Monica Popescu1 Petunia grandiflora Juss. and Nicotiana alata Link & Otto are two of the most widely spread plants on the market for annual potted ornamental plants. In order to identify the most adequate substrate formula we analyzed the effects of different potting growing media used for P. hybrida grandiflora ‘Bravo’ and N. alata ‘Dinamo’ on their photosynthetic capacity, leaf area, and flowering potential. Optimization of growing media formula for petunia and ornamental tobacco was performed by preparing four growing media mixing fallow soil (FS), Biolan peat (BP), acid peat (AP), leaf compost (C), and perlite (P) in different proportions. The physiological potential of petunia and ornamental tobacco was investigated by photosynthesis and respiration rate and chlorophyll pigments in leaves, while the vegetative and flowering phenological stages were evaluated by number of leaves per plant, leaf area, number of flowers per plant and leaf area/flowers ratio. These measurements were significantly influenced by the different potting growing media used in this study. In the flowering stage, the highest photosynthesis rates (8.612 µmol CO2 m-2 s-1) as well as leaf area (1.766 dm2) of petunias were obtained on growing media with 60% biolan peat, 30% acid peat and 10% perlite (BP60-AP30-P10). Flowering responses to growing conditions vary greatly among plants and the biggest number of ornamental tobacco flowers (22 flowers plant-1) was registered as an effect of BP60-AP30-P10 media. Growing media with the BP60-AP30-P10 formula seem to be the most adequate growth substrate to develop profitable crops for petunias and ornamental tobacco with high decorative value. Key words: Flowering potential, growth substrate, photosynthesis. INTRODUCTION In recent years, in Romania, Petunia grandiflora Juss. and Nicotiana alata Link & Otto have become popular annual bedding ornamental plants and economically profitable potted plants cultivated in different growth substrates in greenhouses. Petunias belong to the Solanaceae family and are used in landscape, private garden, and building decoration (Dole and Wilkins, 2004; Arancon et al., 2008; Francescangeli and Zagabria, 2008; Xu et al., 2010), pharmaceutical and cosmetics industry, and phytoremediation (Watharkar et al., 2013). Nicotiana alata (ornamental tobacco) has a good potential for commercial horticulture and is also used in pharmacy or to provide antifungal substances for pathogens control (Gaspar et al., 2014). In Romania the demand for annual ornamental plants is increasing. Numerous studies in petunia species have been described previously. Warner (2010) documented in a greenhouse the influence of temperature and photoperiod on flowering and morphology of petunias. Gerats and University of Pitesti, Faculty of Science, Targu din Vale Street, N° 1, 110040, Pitesti, Romania. * Corresponding author (). Received: 13 May 2014. Accepted: 20 October 2014. doi:10.4067/S0718-58392015000100003 1 Vandenbussche (2005) noted that petunias are often used for physiological studies because these annual plants are characterized by a short life cycle, color diversity, compact plant size, and relatively easy growth. Flowering capacity of petunia plants can be influenced by breeding and cultivation technology (Nishijima et al., 2006). Zhanga et al. (2012) reported that the optimization of nutrient uptake and the influence of environmental factors are necessary to apply efficient cultural management for plant growth and development of petunia production. Growers typically use peat, perlite, vermiculite, sand, fallow land, and various organic and inorganic composted materials to prepare nutritious mixtures for floricultural plant production. Currently, in the entire world, different composting technologies are used for plant production; these are based on several types of wastes such as: municipal organic waste, sewage sludge, agricultural waste, animal manures, and some sorts of industrial waste (Castaldi et al., 2005; Tognetti et al., 2007; Hernández et al., 2010; Ntoulas et al., 2011). Humic acids are one of the natural organic compounds from the soil or composted materials which are included in growth substrates to increase substrate fertility, growth and yield for horticultural crops (Atiyeh et al., 2002; Arancon et al., 2006; Campitelli and Ceppi, 2008; Ahmad et al., 2013). Arancon et al. (2008) studied the effects of different substitution rates for three types of vermicomposts CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 75(1) JANUARY-MARCH 2015 21 (produced from cattle manure, food waste, and paper waste) on the germination, growth, and flowering of petunias in a soilless growth medium. Soilless growing media preparation from different organic materials and waste components is promoted as an alternative to agricultural land and as a way to eliminate the environmental impact of wastes (Garcia-Gomez et al., 2002; Di Benedetto et al., 2006; Civeira, 2010). The production of potted ornamental plants is greatly influenced especially by growth medium components prepared in different proportions. The majority of ornamental plants are cultivated in greenhouses in growth substrates which usually contain different types of peat and perlite. The purpose of this study was to evaluate the effect of some organic growth components used in commercial potting substrates for two popular ornamental plants: Petunia grandiflora and Nicotiana alata. In this paper we performed a comparative analysis of the influence of peat, leaf compost, perlite, and fallow land prepared in different proportions and compositions on plant growth and development. The current study aimed to explain the effect of growing media on these aspects by analyzing some physiological parameters, leaf area, and flowering potential of P. grandiflora and N. alata. In this experiment we optimized the growth substrate composition of P. grandiflora and N. alata in order to provide good agricultural practices to ornamental plant producers. MATERIALS AND METHODS Plant material and culture conditions The study was conducted at the laboratories and greenhouse of the University of Pitesti, Pitesti, Romania. The plant material tested and evaluated in this research were two annual Solanaceae ornamental potted plants: Petunia grandiflora Juss. ‘Bravo’ and Nicotiana alata Link & Otto ‘Dinamo’. The cultivars were selected from the potted plants on the Romanian flower market, based on their popularity, availability, ornamental value, and commercial profitability. The chosen cultivars are characterized by flowering precocity, relatively compact size, uniformity and diversity of flower color, and abundance of flowers. Several types of organic or inorganic materials such as biolan peat, acid peat, leaf com (...truncated)