Micropropagation and In Vitro Inflorescence of Pentas lanceolata

In this study, different concentrations of 6-benzyladenine (BA) on in vitro shoot and inflorescence inductions of P. lanceolata were investigated. The in vivo and in vitro floral characteristics of this plant were also compared. Nodal explants of P. lanceolata were cultured vertically with the cut ends inserted into semi-solid Murashige and Skoog (MS) medium supplemented with 0, 0.5, 1, 2, 4, and 8 mg L–1 BA. The results showed that the explants formed the highest numbers of shoots even when cultured in MS basal medium without any addition of BA, while the shoots formed in the explants cultured in MS medium supplemented with 1 mg L–1 BA were the longest. No inflorescence was found in the shoots cultured in MS medium supplemented with 8 mg L–1 BA, while the highest percentage of inflorescence induction was found in the shoots cultured in the medium supplemented with 0.5 mg L–1 BA. The apperances of in vivo and in vitro flowers of P. lanceolata were the same in many aspects except that the number of flower/inflorescence formed was different. In addition, water accumulation was observed only inside the in vitro flowers. Water deposit in the long tubular structure of P. lanceolata flower could cause anther injury, suggesting that flowers developed in vitro may not always produce pollen.

Evaluation of Native and Nonnative Ornamentals as Pollinator Plants in Florida: II. Floral Resource Value

Consumer demand for novel, visually attractive ornamentals has often overshadowed the functional value plants may provide for flower-visiting insects. As native and nonnative species are hybridized for form, color, flowering, and disease resistance, it is important to assess whether some of these alterations influence plant nutrient quality for foraging insect pollinators. A study was conducted to ascertain the resource value of ornamental cultivars compared with their native congeners. The nectar volume and pollen quantity, viability, and protein content of 10 species of popular herbaceous flowering plants, commonly advertised as pollinator-friendly, were evaluated in northcentral Florida. Each genus encompassed a native and nonnative species, apart from pentas. Native species included blanket flower (Gaillardia pulchella), lanceleaf coreopsis (Coreopsis lanceolata), pineland lantana (Lantana depressa), and scarlet sage (Salvia coccinea). Nonnative species included Barbican™ yellow-red ring blanket flower (Gaillardia aristata ‘Gaiz005’), Bloomify™ rose lantana (Lantana camara ‘UF-1011-2’), mysty salvia (Salvia longispicata × farinacea ‘Balsalmysty’), Lucky Star® dark red pentas (Pentas lanceolata ‘PAS1231189’), ruby glow pentas (Pentas lanceolata ‘Ruby glow’) and UpTick™ Gold & Bronze coreopsis (Coreopsis × ‘Baluptgonz’). Floral rewards differed significantly across species. The native scarlet sage exhibited the largest nectar volume per flower in the summer (2.13 ± 0.17 µL), followed by the nonnative mysty salvia (1.26 ± 0.17 µL). In the fall, ruby glow pentas exhibited the largest nectar volume per flower (1.09 ± 0.17 µL) compared with all other ornamentals. The composite flowers of the native and nonnative blanket flower and coreopsis species had the lowest nectar volume per flower regardless of sampling date. Likewise, ruby glow pentas displayed the highest quantity of pollen grains (96.29 ± 0.12) per sample, followed by Lucky star pentas (52.33 ± 0.12), and Barbican blanket flower (50.98 ± 0.12). Pollen viability was similarly high (92% to 98%) among all species, apart from Bloomify rose lantana (20%) and pineland lantana (48%). Pollen protein content was highest in Uptick coreopsis (11.378 ± 1.860 μg/mg dry weight) and Lucky star pentas (10.656 ± 3.726 μg/mg dry weight), followed by lanceleaf coreopsis (7.918 ± 1.793 μg/mg dry weight). These results largely showed that the nonnative ornamentals selected provided resource-rich floral rewards, comparable to native congeners. Still, care should be taken in making similar assessments of other modern floral types.

Pentas lanceolata (Egyptian starcluster).

Pentas lanceolata is a fast growing, small to medium-sized herbaceous shrub that has become very popular as an ornamental and potted plant due to its colourful flowers. It is adapted to grow in a wide range of environmental conditions and tolerates a fair amount of drought. P. lanceolata has been intentionally introduced into many tropical and subtropical regions from where it has escaped to colonize predominantly disturbed sites, open grounds and roadsides near cultivation areas. Once established this species may become dominant in some open areas and can form monospecific stands with the potential to outcompete and exclude native plant species and other early successional vegetation. To date, P. lanceolata has been listed as invasive only in insular ecosystems in Hawaii, Anguilla, Norfolk Island, Mayotte Island and French Polynesia. In Hawaii, it has recently been noted spreading across the Big Island; on Maui, it volunteers in scrub areas and steep banks.

Applying Dickson Quality Index, Chlorophyll Fluorescence, and Leaf Area Index for Assessing Plant Quality of Pentas lanceolata

Plant quality greatly relates to the seedling vigor (SV), survival and growth of plants after transplantation. The objective of this study was to use the nondestructive measurements of chlorophyll fluorescence (ChlF) and leaf area index (LAI) as SV indices for star cluster (Pentas lanceolata). Plants were grown in potting soil under nature sunlight for 90 d. A total of 13 morphological and physiological parameters were selected for measurements. Among them, root growth potential (RGP) was the best predictor for SV in all tested plants. Plants were separated into 5 RGP groups based on the number of new roots, and remaining parameters were also separated into those same levels. The trends and rates of increase from levels 1 to 5 in Dickson quality index (DQI), LAI, total dry mass, and ChlF were all similar to the RGP index. Although RGP and DQI are frequently used as indices for SV, these measurements are time-consuming and require sample destruction. Consistent and strongly high correlations were observed among DQI, LAI, and ChlF, demonstrating the applicability of these indices for measuring SV in star cluster. The measurements of LAI and ChlF were predicted using multiple variables from validation datasets, and showed novel and useful parameters for examining the SV of star cluster.