Plant collections at the PNH which approximately total to 180,000 mounted and accessioned specimens include angiosperms (flowering plants), gymnosperms (cone-bearing plants), pteridophytes (ferns and fern allies), bryophytes (mosses, hepatics and liverworts), algae, and fungi. The Botany Division which curates and maintains the plant collections also conducts research studies in basic science including taxonomy, revisionary and monographic studies and floristics, and applied science including economic and ethnobotany, allergenic plants, conservation biology, and bioinformatics. Collaborative research activities are also being conducted in the fields of pharmacognosy and pharmacology. The staff also spearheads the establishment of botanical gardens for conservation and educational purposes.
The collections represented in this handbook were chosen on the basis of their conservation status (e.g. rarity) as well as their economic, cultural, and historical significance.
The sea and the shore are the habitats of marine algae. Here, the red and the brown algae are the major photosynthetic organisms, while green algae play this role in the freshwater environment. These three groups occur in both freshwater and marine environment. Some green algae are even terrestrial. Green algae are believed to be the predecessors of the land plants because they share similar characteristics with them including chlorophyll a and b and starch as a form of food reserve. Diverse types of life cycle occur in the different members of the algal group. Their plant body is called a thallus; it does not have true roots, stems, or leaves.
Algae are important source of food in many parts of the world [e.g. kelps, sea lettuce (Ulva sp.)]. They provide necessary salts and other supplementary vitamins and minerals. Kelps are the source of alginates, which are used as thickening agents and stabilizers in the food, textile, cosmetic, paper and pharmaceutical industries. They are also used directly as fertilizers in some regions and in the preparation of agar. Agar which is used to make capsules for drugs and vitamins, base of cosmetics, dental impression material, and a culture medium for bacteria and other cells, perhaps is the most important direct commercial application of any algae.
The Ferns and Their Allies
Pteridophytes are vascular plants that are similar to seed-bearing plants by the presence of vascular tissues, phloem and xylem. They, however, differ from the latter by having spores as the major dispersal units, characteristics they share with bryophytes and fungi. Ferns have a pronounced alternation of phases in their life cycle, the sporophyte (the spore-bearing phase) and the gametophyte (the gametangia and gamete-bearing phase). The sporophyte is the more dominant phase represented by the plants we see in the forests. The gametophyte is very reduced, sometimes microscopic multicellular, one-cell thick organism that later develops gametangia producing eggs and sperms. One germinating spore can potentially start a population because it can develop into a gametophyte that produces both the eggs and sperms.
One of the most economically important ferns, Azolla, a species that naturally fixes nitrogen, occurs in rice paddies in Asia. Some species are highly priced ornamentals, some are used in native handicrafts, and still others are used as food.
An approximately 10,000 species of pteridophytes are known in the world today. About 1,100 species occur here in the Philippines, nearly 30% of which are endemic.
However, 79 species or about 26% of our endemic taxa are only known from one collection and has never been recollected. With the dwindling forest resources, the major habitat of these plant group, it is not surprising that most of these single-collection-endemics are already extinct in the wild or extinction is inevitable.
Gymnosperms and Angiosperms
Seed-bearing plants consist of two major groups, the gymnosperms (e.g. pines, cycads, ginkgo, yew, alder) and the angiosperms or flowering plants (e.g. bananas, grasses, mangoes, and orchids). Gymnosperms are more concentrated in high altitude vegetation types whereas angiosperms are present in almost all major vegetation types. Angiosperms differ from gymnosperms by having flowers and the seeds are inside the fruits. The development of the fruit in angiosperms had been responsible for their greater dispersability than any other groups, hence their successful colonization of more diverse niches. Seed dispersal is accomplished by wind, animals, or water current. Moreover, the loss of flagella on sperms allows fertilization without the water medium (unlike the algae, bryophytes, and pteridophytes). Pollination, the process of transferring pollen grains from the anther to the stigma of flowers is responsible for fertilization to take place in seed-bearing plants. This is possible through pollinating agents including wind, insects and other animals, and water.
The seed plants are the most economically important species of plants. They are the major sources of food (cereals from grains, fruits, and vegetables) and medicines. Ecologically, they absorb pollutants in the atmosphere and convert some of them into oxygen and water. Rainforests are fast disappearing on the earth’s surface and it is not impossible for the earth’s ecosystem to collapse because of overutilization by human beings of forest resources.
An approximately 235,000 species of flowering plants have been described and named today. Some 8,000 or more species occur in the Philippines.
Among the local flora are anemophilous plants whose pollen grains are carried primarily by wind. When they pollinate, they scatter pollen in the atmosphere and cause misery to allergy sufferers. These are hypersensitive people who are afflicted with asthma, rhinitis, alveolitis, conjunctivitis and dermatitis.
In cone-bearing plants pollen grains are formed in the sporangia attached to the male cones. In the flowering plants on the other hand, they are produced in the anther. Most flowers that produce airborne pollen have anthers that are long and flexuous allowing them to move freely in the wind.
The morphology of pollen grains can be described so that one species of plant may be distinguished from another. For example, the pollen grain of foxtail (Pennisetum polystachyon (L.) Schult.) is monoporate. The exine or wall appears smooth under a light microscope but if seen with a scanning electron microscope it is divided into frustillae. The pollen grain of ‘makahiya’ (Minosa pudica L.) is a tetrad and the exine of each grain is areolate. The pollen grain of pigweed (Amaranthus spinosus L.) is pantoporate (with many pores distributed on its surface).
Fortunately, pollen grains that cause respiratory allergy are the very same pollen used in skin-testing (diagnosis) and treatment (immunotherapy) of the disease. Pure, clean, and dry pollen are in demand by pharmaceutical industry. Through a research project funded by the National Research Council of the Philippines, allergy crops may be cultivated to produce pollen products. This may help increase the dollar net flow if indigenous pollen materials become commercialized locally.
They may look more like plants but fungi are more closely related to animals than plants! Unlike the plants that store food as starch, the food reserve in fungi is glycogen and their cell walls are chitinous (chitin is the same substance found in the carapaces of crabs and exoskeletons of insects!). Fungal reproduction is by means of spores that are dispersed by wind. These spores develop into non-photosynthetic fungal bodies called hyphae, a mass of which is called a mycelium. Since they cannot make their own food through photosynthesis, fungi obtain their food from their hosts as parasites, from dead organic matter as saprophytes, or as mutualistic symbionts (with algae, in the form of lichen).
Fungi, like bacteria, are the principal decomposers of the biosphere. They are responsible for breaking down organic matter and subsequently returning them back to the soil to be recycled. They are important commercially in pharmaceutical industries as sources of antibiotics (e.g. penicillin) and cyclosporine (wonder drug). Cyclosporine reduces the probability of organ transplant rejection by suppressing the immune reaction that causes rejection. Some species of fungi are edible and sources of priced delicacies, however, some are deadly poison (e.g. Amanita). Some fungi are also known for being nasty commercial pests, parasites to animals and human beings (causing athlete’s foot, ringworm or dandruff). They also produce carcinogenic substances such as aflatoxin that attack peanuts.