Crossandra

Abstract: The pollen of 30 species, five subspecies and one possible hybrid of Crossandra Salisbury, together with that of one species of Crossandrella C. B. Clarke, was examined with light microscopy, scanning electron microscopy and selectively with transmission electron microscopy. A remarkable range of exine stratification was discovered and this was used as the basis for the delimitation of six pollen types. Pollen Types I-V are found in Crossandra and Pollen Type VI in Crossandrella. The relationships between these Pollen Types and the sectional classification of Crossandra are discussed. The pollen of one species, Crossandra flava, was found to be highly variable, with both ridged and unridged pollen, and some abnormally shaped sterile pollen grains. Three evolutionary trends are recognised in the pollen morphology of Crossandra and Crossandrella and these are discussed, together with functional aspects.

Abstract: In this study, areca palm (Dypsis lutescens), crossandra (Crossandra infundibuliformis), pentas (Pentas lanceolat), and philodendron (Philodendron) ‘Hope’ plants were transplanted into containers filled with four growing substrates and watered daily, every 2 days, or every 3 days using subirrigation or overhead irrigation. Plants were grown in either a pine bark/sedge peat/sand substrate (BSS), Metro-mix 500 (MM), Pro-mix GSX (PM), or a 60% biosolid substrate (SYT). For both irrigation systems, final shoot dry weight of pentas, crossandra, philodendron, and areca palm plants in each substrate was greatest for plants watered every day and least for plants watered every 3 days. At all three irrigation frequencies, pentas, crossandra, and philodendron shoot dry weight in subirrigated pots filled with PM was greater than in overhead watered pots filled with PM. PM had the highest total pore space and moisture content of the four substrates examined. There was no difference in pentas, crossandra, or philodendron shoot dry weight between the irrigation systems, at all three irrigation frequencies, when plants were grown in BSS, MM, or SYT. However, for all four substrates and at all three irrigation frequencies, areca palm shoot dry weight was greater in overhead watered pots than in subirrigated pots. The final substrate electrical conductivity (EC) in all four subirrigated palm substrates was more than double the concentrations in overhead watered palm substrates. In this study, largest pentas, crossandra, and philodendron plants were grown in pots filled with PM and subirrigated daily, while largest areca palm plants were grown in pots filled with MM or SYT and watered overhead daily.