Chapter 7
Communication
7.1 Flow Networks
Large organisms need to develop special internal exchange systems to supply nutrients and remove waste. Mere diffusion already becomes ineffective on millimeter
distances, and the supply path, proportional to the volume-to-surface ratio, increases
with size. This necessitates more effective internal communication highways with a
large surface area and transport mechanisms that are more efficient than diffusion.
Branched structures, either in the form of what mathematicians call trees (because
real trees and their roots are like this), or connected into networks, have a very large
surface area for a given volume (Sect. 3.6), and therefore work most efficiently when
this task is set. Within branches, material is carried by flow rather than diffusion,
which is not only faster but can be more efficiently directed to the relevant destinations. Both animal and plant branched structures are graded, becoming thinner as
they branch, in accordance with the decreasing flux.
Plants grow flat leaves with a large surface area that capture sunlight. They did
not have a nutritional problem while they grew under water, but after venturing onto
dry land about half an eon ago they could not survive without procuring moisture
and minerals from soil, and had to develop branched supply systems both below and
above the ground. Plant roots and stems or trunks, like other phylla, are initiated by
apical meristems (Fig. 6.16, left), and elongate and thicken to satisfy the plant’s
needs, driven by auxin and other hormones. Roots do not form ordered patterns
like those discussed in Sect. 6.6, and such patterns are only rarely distinguishable
in branches of trees. The distinction between the two kinds of branched structures
may blur when roots emerge above ground and trunks penetrate below, which is
particularly evident in mangroves growing in waters raised and lowered by tides.
The branched root system (Fig. 7.1, left) combines its nutritional function with supporting the plant mechanically, and this is also helped by having a large surface area
for stronger contact with the soil. The large surface area of stems serves to support
larger numbers of photosynthetic leaves in such an arrangement that they do not
shade one another.
105
© Springer Nature Switzerland AG 2020
L. Pismen, Morphogenesis Deconstructed, The Frontiers Collection,
https://doi.org/10.1007/978-3-030-36814-2_7
Communication
7.1 Flow Networks
Large organisms need to develop special internal exchange systems to supply nutrients and remove waste. Mere diffusion already becomes ineffective on millimeter
distances, and the supply path, proportional to the volume-to-surface ratio, increases
with size. This necessitates more effective internal communication highways with a
large surface area and transport mechanisms that are more efficient than diffusion.
Branched structures, either in the form of what mathematicians call trees (because
real trees and their roots are like this), or connected into networks, have a very large
surface area for a given volume (Sect. 3.6), and therefore work most efficiently when
this task is set. Within branches, material is carried by flow rather than diffusion,
which is not only faster but can be more efficiently directed to the relevant destinations. Both animal and plant branched structures are graded, becoming thinner as
they branch, in accordance with the decreasing flux.
Plants grow flat leaves with a large surface area that capture sunlight. They did
not have a nutritional problem while they grew under water, but after venturing onto
dry land about half an eon ago they could not survive without procuring moisture
and minerals from soil, and had to develop branched supply systems both below and
above the ground. Plant roots and stems or trunks, like other phylla, are initiated by
apical meristems (Fig. 6.16, left), and elongate and thicken to satisfy the plant’s
needs, driven by auxin and other hormones. Roots do not form ordered patterns
like those discussed in Sect. 6.6, and such patterns are only rarely distinguishable
in branches of trees. The distinction between the two kinds of branched structures
may blur when roots emerge above ground and trunks penetrate below, which is
particularly evident in mangroves growing in waters raised and lowered by tides.
The branched root system (Fig. 7.1, left) combines its nutritional function with supporting the plant mechanically, and this is also helped by having a large surface area
for stronger contact with the soil. The large surface area of stems serves to support
larger numbers of photosynthetic leaves in such an arrangement that they do not
shade one another.
105
© Springer Nature Switzerland AG 2020
L. Pismen, Morphogenesis Deconstructed, The Frontiers Collection,
https://doi.org/10.1007/978-3-030-36814-2_7