Transport in Plants
Over 450
million years ago (the Ordovician period in Paleozoic era) plants migrated from
their own sophisticated water world to newly formed land. The land had harsh
environment; water availability was deeper and so plants struggled for getting
water for their very existence. Some of them failed to survive and rest adopted
themselves to the new world. The biggest adaptations followed for their
survival was building their own water absorbing systems to draw water from deep
inside the land. The creation and updating of water absorbing system (vascular
tissues) led to the diversity of the plant kingdom. The gregarious growth of
prehistoric pteridophytes, gymnosperms and present-day flowering plants led to
the biggest challenge in the transport of water from root to several meters
high trees against gravity. In this chapter, we will study the events taking
place between the gain of water in roots and loss in leaves and the mechanisms
behind the basic physical and biological processes in the movement of water,
gases and minerals in plants. Further, we study how food material synthesized
in the leaf can be transported to various utilizing and storage areas against
struggles and challenges.
Plants and animals evolved separately but developed comparable
structures to control transport of water and dissolved chemicals. But whose
transport system is optimally designed to offer selective advantage? In plants,
transport through xylem has allowed growth in height and colonization of
diverse habitats and the system has to be extensive as Photosynthesis requires
water. Murray’s law predicts the thickness of branches in transport networks,
such that the cost for transport and maintenance of the transport medium is
minimized. This law is observed in the vascular and respiratory systems of
animals, xylem in plants, and the respiratory system of insects. Further
research in this area will improve our understanding of natural world.
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