Methods for the Study of Leaf Anatomy in Palms
Abstract
Large size, hardness, combinations of thick-walled fibers and sclereids with thin-walled parenchyma cells, and the occurrence of silica, calcium oxalate, and tannins make anatomical preparations of palm leaves difficult. Samples for anatomical study should encompass one-half a pinna or a comparable portion from palmate and entire leaves including the midrib, all large ribs, and the margin. Similar pieces from herbarium specimens are reconstituted in glycerin alcohol, aerosol OT and distilled water (10:3:90). All samples are fixed in formol-acetic-alcohol (FAA) but stored in glycerin alcohol to minimize hardening. Transverse and longitudinal sections IS microns thick, epidermal macerations, and pieces for clearing and for scanning electron microscopy are prepared from the FAA fixed material. Samples for electroscanning are gradually changed to 100% acetone, critical point dried with CO 2 , and coated with 100–300 angstroms of gold. Leaf material for microtomy is treated with hydrofluoric acid, embedded in Paraplast, and sectioned at 15 microns at a temperature of 7.2 C. Paraplast sections are floated directly on a modification of Sass' Adhesive III, mounted unstained or stained in safranin and fast green, and observed in polarized light. Epidermal peels are prepared by soaking pieces 5 mm square for 12-24 hours in undiluted bleach. Pieces for observation of transverse veins are cleared by treatment in 5% sodium hydroxide in a 60 C oven, washed rapidly in three changes of distilled water, and placed in one-third strength commercial bleach until clear. The same procedures can be used to prepare reproductive material for anatomical observations, but time schedules must be increased for larger specimens.