Chemistry Reference
In-Depth Information
Seeds and roots
have great importance for the abiotic stress tolerance during vegetation
period (drought, high temperature). Seed traits determine plant growth on the beginning of
vegetation period; especially by seed vigor, and by seed storage conditions. On the other
hand the roots are influenced by seeds quality on the start of plant growth, especially root
morphology, i.e. length, surface, deep of penetration of the roots and also root weight,
number of root tips, number of root hairs, number of lateral roots and density of roots and
modified by environmental conditions. Roots affect plants on the whole vegetation period
and from this point of view influence growth and development of new seed generation. The
level of theses relations depends on the environmental conditions; it means on the influence
of seed provenance.
3. Short root and seed history step by step
When we skip the period 3.5 billion years ago, when the cyanobacteria was only on the
Earth, the history of the plants can be divided into four periods:
1.
Thalassiofyticum- (until 442 million years BC) period of
Algae
2.
Paleofyticum (442-248 million years BC)
3.
Mesofyticum (248-97 million years BC)
4.
Cenofyticum (97 million years BC until today)
In the first part of
Paleofyticum
, the
“older” paleofyticum
(442-354 million years BC) the
plants spread from the water on the land. In this time formation of roots started, which
enabled to live on the earth's surface. In the
“younger“ paleofyticum
(354-298 million years
BC) is characterized by seed development [16, 63].
The negative impact of environmental conditions -long period of the drought conditions- is
reflected strongly in evolution. “Invention” of the seeds improved the chance of species
survival thanks to the better dispersion of seeds and by this way expansion of the species.
The evolution of plants is connected with ability to survive dry and cold period of plant
growth. Some mechanisms were evolved, started with tissue specialization, through
dormancy evolution to post harvest maturation.
In this period developed psilophyta, pteridophyta and plant ferns gymnosperms. Among
the ferns (
Pteridophyta
) are classified plants lycopodium (
Lycopodiophyta
), horsetail
(
Equisetophyta
), tree ferns (
Polypodiophyta
) and plants (Progymnospermophyta) as cycads
and conifers.
After transition of plants on the earth's surface
the influence of abiotic stressors prevail
rather than biotic factors. Gradually, however, grew relationship among different species of
the plants either negative or positive and between plants and other organisms
In
Mesofyticum
ancestors of the modern ferns appeared (fern seed plants, cycas, benetits,
and conifers).
Cenofyticum
is the last period of plant development, characterized by spreading of
angiosperms. This period lasts until today. As examples there are given three examples of
