Fibre cables in the lacunae of Typha leaves contribute to a tensegrity structure.

BACKGROUND AND AIMS: Cables composed of long, non-lignified fibre cells enclosed in a cover of much shorter thin-walled, crystal-containing cells traverse the air chambers (lacunae) in leaves of the taller species of Typha. The non-lignified fibre cables are anchored in diaphragms composed of stellate cells of aerenchyma tissue that segment the long air chambers into smaller compartments. Although the fibre cables are easily observed and can be pulled free from the porous-to-air diaphragms, their structure and function have been ignored or misinterpreted. METHODS: Leaves of various species of Typha were dissected and fibre cables were pulled free and observed with a microscope using bright-field and polarizing optics. Maximal tensile strength of freshly removed cables was measured by hanging weights from fibre cables, and Instron analysis was used to produce curves of load versus extension until cables broke. KEY RESULTS AND CONCLUSIONS: Polarized light microscopy revealed that the cellulose microfibrils that make up the walls of the cable fibres are oriented parallel to the long axis of the fibres. This orientation ensures that the fibre cables are mechanically stiff and strong under tension. Accordingly, the measured stiffness and tensile strength of the fibre cables were in the gigapascal range. In combination with the dorsal and ventral leaf surfaces and partitions that contain lignified fibre bundles and vascular strands that are strong in compression, the very fine fibre cables that are strong under tension form a tensegrity structure. The tensegrity structure creates multiple load paths through which stresses are redistributed throughout the 1-3 m tall upright leaves of Typha angustifolia, T. latifolia, T. × glauca, T. domingensis and T. shuttleworthii. The length of the fibre cables relative to the length of the leaf blades is reduced in the last-formed leaves of flowering individuals. Fibre cables are absent in the shorter leaves of Typha minima and, if present, only extend for a few centimetres from the sheath into the leaf blade of Typha laxmannii. The advantage of the structure of the Typha leaf blade, which enables stiffness to give way to flexibility under windy conditions, is discussed for both vegetative and flowering plants.

A constructed wetland model for synthetic reactive dye wastewater treatment by narrow-leaved cattails (Typha angustifolia Linn.).

Textile wastewater is contaminated by reactive dye causing unattractive levels of wastewater color, high pH and high salt content when discharged into public water systems. Decolorization of textile wastewater by plant, phytoremediation, is an alternative, sustainable method which is suitable for long term operation. Narrow-leaved cattails are one species of wetland plant with efficiency for decolorizing and remediating textile wastewater. In addition, chemical oxygen demand (COD) can be lowered and dye residue can be removed. The plant also showed a good salt tolerance even after being exposed to a salt solution for 15 days. The narrow-leaved cattails were set up in a constructed wetland model with a vertical flow system operating from bottom to top for synthetic reactive dye wastewater (SRDW) removal. Narrow-leaved cattails could achieve the removal of SRDW at approximately 0.8 g(SRDW) m(-2) day(-1). Decolorization of SRDW by this plant was approximately 60%. The advantage of this method is that it is suitable for textile wastewater management and improvement of wetland. These plants could lower COD, remove dye, sodium and total dissolved solids (TDS) whereas other biological and chemical methods could not remove TDS and dye in the same time. These results suggested that the spongy cell structure of this plant has the ability to absorb large amounts of water and nutrients. Physico-chemical analysis revealed increasing amounts of sulfur, silicon, iron and calcium in the plant leafs and roots after exposure to wastewater. Proteins or amide groups in the plant might help in textile dye removal. Regarding decolorization, this plant accumulates dye in the intercellular space and still grows in this SRDW condition. Hence, it can be noted here that narrow-leaved cattails are efficient for textile dye wastewater treatment.

Spiralling upward.

Thin vertical leaves often manifest twist. Perhaps the most prominent example of this is in Typha sp., but such twist is also apparent in Narcissus, Pancratium and many other genera. Such a blade is often referred to as a "spiral leaf". We will indicate the mechanical advantage afforded to the leaf by this arrangement, i.e. that it permits the leaf to achieve a greater height without losing stability, that is bending over due to its own weight. We quantify this gain and show how by a simple experiment it can be shown that the advantage is indeed utilized in nature. Typha domingensis is offered as an example.

Epifluorescent and histochemical aspects of shoot anatomy of Typha latifolia L., Typha angustifolia L. and Typha glauca Godr.

Using epifluorescent and histochemical techniques, we examined anatomical differences in the shoot organs of Typha latifolia, T. angustifolia and T. glauca. The leaf lamina of T. latifolia and T. glauca had enlarged epidermal cells and a thickened cuticle above the subepidermal vascular bundles; that of T. angustifolia lacked these characteristics. Leaf sheaths were similar among the species and all lacked the epidermal thickenings found in the lamina. The fertile stems had typical scattered vascular bundles with a band of fibres that was most prominent in T. glauca. The sterile stems were only 1 cm in length and contained a multiseriate hypodermis and a uniseriate endodermis over part of their length. The rhizomes were similar except for a pronounced band of fibres surrounding the central core in T. angustifolia. The rhizome was also characterized by an outer cortical region with a large multiseriate hypodermis/exodermis and a uniseriate endodermis with Casparian bands, suberin lamellae and secondarily thickened walls.