In plants, suspensors are found in
zygotes in
angiosperms, connecting the endosperm to an embryo. Usually in
dicots the suspensor cells divide transversally a few times to form a filamentous suspensor of 6–10 cells. The suspensor helps in pushing the embryo into the endosperm. The first cell of the suspensor towards the
micropylar end becomes swollen and functions as a
haustorium. The haustorium has wall ingrowths similar to those of a
transfer cell. The last of the suspensors at the end of the embryo is known as
hypophysis. Hypophysis later gives rise to the
radicle and root cap. During embryo development in angiosperm seeds, normal development involves asymmetrical division of the unicellular embryo, inducing polarity. The smaller terminal cell divides to become the
proembryo while the larger basal cell divides laterally to form the suspensor. The suspensor is analogous to a placental mammalian's
umbilical cord. Comparative studies make it clear that the suspensor is more than a passive stalk.
Microscopy and physiological experiments show that it physically "pushes" the embryo proper deeper into the endosperm cavity and simultaneously forms a living bridge through which nutrients and
growth regulators move from maternal tissues to the embryo. Specialised anatomical features enhance this transport capacity: many suspensors bear extensive
cell wall ingrowths that amplify membrane surface area, haustorial outgrowths that penetrate adjacent tissue, and dense fields of
plasmodesmata for
symplastic flow. In most dicot embryos the basal (
micropylar) suspensor cell becomes exceptionally large. This swollen cell functions as a haustorium, acting as the main interface with surrounding seed tissues and showing the highest
metabolic activity within the suspensor. Its transfer-cell-like wall ingrowths, together with the haustorial projections noted above, account for the long-recognised observation that the suspensor actively imports rather than merely suspends the developing embryo. More recent research shows that the suspensor acts as the embryo's first support organ: it helps establish the embryo's head-to-root axis, funnels sugars and other nutrients from surrounding tissues, makes its own growth hormones (high levels of
auxin and
gibberellins have been detected), and then dismantles itself through a tightly regulated burst of
programmed cell death once its brief task is complete. ==References==