Month: September 2022

FOLDING ORIGAMI is not the simplest of projects, especially if the folding parts get damaged by weather or predators. Folding and unfolding of flowers is a complex and biologically costly venture. It is surprising that nature has elected to fold and unfold such seemingly delicate structures as flowers so frequently. View in LinkedIn

DIVERGENT SOLUTIONS. "Depending on the species, opening may relate to the development of tissues adjacent to the flower, for example, opening may require growth of the pedicel, as in several species in the Iridaceae; or it may require forced separation or abscission of covering parts, such as bracts or sepals." https://lnkd.in/eTEzGE9 View in LinkedIn

ELEGANT ENGINEERING. "In some flowers, for example in Oenothera spp., the sepals are connected by a zipper‐like mechanism whereby cells at the sepal margins are tangled. Due to the force of the growing petals this entanglement is broken and the petals are suddenly released. In several other species the sepal margins are tightly held together by ridges, which also delay opening until the growing petals overcome their resistance. This also results in rapid opening." https://lnkd.in/eTEzGE9 View in LinkedIn

"FLOWER OPENING depends on petal movements, of which at least four types can be distinguished. (1) Opening is due to reversible ion accumulation, and independent of elongation growth; (2) it depends on cellular death in a specific area of the petal; (3) it is due to loss of water during the day and refilling during the night; and (4) it depends on differential growth." https://lnkd.in/eTEzGE9 View in LinkedIn

INITIATED BY DARWIN. "In his book entitled The Power of Movement in Plants, Darwin (1880) described many examples of “sleep movements of leaves” and provided a “List of Genera, including species the leaves of which sleep”. Among these, he noted that the legume family “includes many more genera with sleeping species than all the other families put together.” He also described a specialized organ, called a joint, cushion, or pulvinus responsible for such movement. https://lnkd.in/eE__XBs View in LinkedIn

"THE PULVINUS is an enlarged motor organ at the base of leaves found in many leguminous plants. It has been observed to force the movement of leaves in heliotropic, seismonastic, and nyctinastic patterns." https://lnkd.in/e9s_fPH View in LinkedIn

MASSIVE WATER FLUX. "The pulvinus is the organ responsible for the nyctinastic leaf movement. It is a specialized structure located at the base of the petiole of leaves or the petiolule of leaflets in the case of compound leaves. During leaf opening, leaflets move downward by the simultaneous increase of turgor pressure in extensor and decrease in flexor cells. During closing, the inverse occurs, extensor cells shrink, and flexor cells swell, moving leaflets upward. These turgor changes in the motor cells are caused by ion movements followed by massive water flux across the plasma membrane." https://lnkd.in/eE__XBs View in LinkedIn

IONS DRIVE WATER. "Swelling is caused by proton pump-driven accumulation in the cytoplasm of K+ and Cl−. This increase in solute concentration lowers water potential inside the cell, and thus drives the entrance of water in the cell. Shrinking is caused by a passive leaking of solutes that is accompanied by water loss. It is currently accepted that the osmotic volume changes of motor cells are analogous to those of stomatal guard cells." https://lnkd.in/eE__XBs View in LinkedIn

GENETIC REGULATORS. "The formation of the pulvinus in legumes is likely to be regulated by a conserved genetic network orchestrated by the ELP1/APU/SLP1 genes. In the absence of these genes, the small, isodiametric, epidermal pulvinus cells with a highly convoluted surface are replaced by much larger and elongated petiole-like epidermal cells." Numerous studies of mutant flowers that cannot close at night led to this discovery. https://lnkd.in/eE__XBs View in LinkedIn

IONIC GRADIENTS AND PHOTOPERIODS. "In heliotropism, upon light exposure, an asymmetric turgor gradient formed between the adaxial and abaxial motor cells leads to leaf movement. Potassium ion influx coupled with chlorine ion is powered by a proton gradient and results in osmotic influx. In addition to heliotropism, the pulvinus changes turgor for nyctinastic leaf folding, and is affected by alterations in the length of the photoperiod." https://lnkd.in/e9s_fPH View in LinkedIn