Sauer - 1993 - Historical geography of crop plants, a select rost

206 Historical Geography of Crop Plants: A Select Roster
artifacts. They also produce large quantities of edible grain but only at intervals
of many years, so the grain is taken as a bonus (or a curse, if it brings forth
an irruption of rats) and is not relied upon as a regular crop. Although some
bamboos are planted sporadically, reproduction of the populations is not generally
dependent on human aid.
The various tribes of herbaceous grasses are of far greater importance.
Harlan (1982) wrote that mankind is sustained more by the grasses than by
plants of any other family. About Ѵз of the calories and half of the protein
in human nutrition come from cereal grains. Also, grasses are paramount in
feeding the livestock that supply most of our meat and dairy products.
By definition, cereal grains are the caryopses of grasses, i.e., single-seeded
fruits in which the ovary wall and the seed coat are fused around the embryo
and endosperm. People and other animals may eat the caryopses whole, but
the main nutrition comes from the endosperm. Endosperm is a triploid tissue,
inheriting two chromosome sets from the mother plant and one from the pollen
pai’ent. In that respect, grass seeds are like angiosperm seeds in general. The
special value of the grasses as seed crops depends on how quickly, abundantly,
and easily the crop can be grown. This is largely due to special ecological
adaptations inherited from the wild ancestors. The progenitors of our staple
cereal crops all evolved as eeological pioneers in naturally open habitats. They
were preadapted to grow in the full sun and mineral soil of tilled fields.
Although the great majority of wild grass species are perennials, as a rule the
ancestors of domesticated cereals are annuals, which complete their life cycles
in a single growing season. They allocate a remarkably large share of their
photosynthate to seed production instead of vegetative growth, a crucial legacy
for the staple grain crops.
Noncereal grass crops, e.g., sugar cane and pasture grasses, are also descended
from pioneer species of streambanks or other naturally open habitats,
but they ai'e perennials capable of vigorous vegetative reproduction. The
pasture grasses inherit adaptations for survival under grazing and trampling
by hoofed animals that probably coevolved with large ungulates in the Tertiary.
ORYZA — RICE (Bender 1975; Burkill 1935; Chang 1976, 1989; Harlan
1975; Morinaga 1960; Patiño 1969; Rutger and Brandon 1981; Simoons
1990; Vishnu-Mittre 1977; Watson 1983)
The genus of domesticated rice includes about 20 wild species, natives of
h’opical and subtropical regions all around the world. The species are not well
adapted for long-range dispersal, and the migrational histories behind these
huge disjunctions are obscure.
Wild Oryza species generally grow as emergent aquatics in seasonally or
permanently flooded sites. Like other marsh and swamp plants, they require
special mechanisms to supply air to root systems growing in anaerobic sod.
The leaf epidermis of Oryza is nonwettable, so a continuous film of air extends