Year: 2022

DECIDUOUS TREES. "Here much of the plant body is made up of dead tissues, the canopy is renewed and discarded every year, root systems turn over, and reproduction takes place repeatedly over decades, centuries or even millennia. In iteroparous species, such as trees and clonal plants, there is a disjunction between the lifespans of the whole and parts." https://lnkd.in/dPac2Jv View in LinkedIn

FOREST TURNOVER. "Molecules, cells, phytomers, individuals and even whole floras typically turn over. Turnover is defined as flux through a pool. In the case of leaf turnover, the pool is the canopy. Newly initiated leaves are recruited to the canopy, grow and mature, become senescent and ultimately die and leave the pool." https://lnkd.in/dPac2Jv View in LinkedIn

SINKS. "A sink is defined as a net importer of nutrients (nitrogen (N), phosphorus (P), potassium (K), sulfur (S) and other minerals) and assimilates carbon (C) derived directly or indirectly from photosynthesis. Developing seeds, bulbs, tubers and other structures that accumulate storage compounds are strong sinks, as are expanding leaves and branches during vigorous vegetative growth." https://lnkd.in/dPac2Jv View in LinkedIn

SOURCES. "Organs that supply the precursors for sink metabolism are sources. Sources and sinks communicate through the vascular system. During development of the endosperm of cereal grains and the parenchyma of potato tubers, large amounts of starch are accumulated. These organs are supplied via the phloem with assimilated C mostly fixed by current photosynthesis." https://lnkd.in/dPac2Jv View in LinkedIn

SINKS TRUMP SOURCES. "A semelparous plant dies because its sink tissues kill its source organs by a kind of starvation, by induction of senescence in response to nutrient diversion or by export of a ‘death hormone'." (Semelparous organisms have only one reproductive episode before death). https://lnkd.in/dPac2Jv View in LinkedIn

SINK-SOURCE CHATTER. "Senescence is responsive to communication between sources and sinks in which sugar signalling and hormonal regulation play central roles. Monocarpy and polycarpy represent contrasting outcomes of the balance between the determinacy of apical meristems and source–sink cross-talk. Even extremely long-lived perennials sustain a high degree of meristem integrity." https://lnkd.in/dPac2Jv View in LinkedIn

TRANSITION POINT. "The bifunctionality of Rubisco as both a photosynthetic enzyme and a reserve of mobilizable N is reflected in the dual role of foliage: leaves are organs of storage as well as assimilation, and the initiation of senescence may be considered to be the point of transition from C to N source." https://lnkd.in/dPac2Jv View in LinkedIn

AUTO-DIGESTION. "Young, actively growing vegetative sinks, and storage organs accumulating reserve proteins, have a rapacious appetite for N. When the demand cannot be met by import from the rhizosphere alone, N is withdrawn from older tissues. In extreme cases – monocarpic reproduction, for example – N remobilization from older tissues can occur on such a scale that the plant ‘self-destructs’." https://lnkd.in/dPac2Jv View in LinkedIn

SHUNTING THE GOODIES. "Internal redistribution of N between sources and sinks can also account, at least in part, for other patterns of senescence. Before leaf fall in deciduous species, salvaged N is transferred to bark tissues, where it accumulates as defined storage proteins that will be mobilized to provide amino acids to support the resumption of growth in the spring." https://lnkd.in/dPac2Jv View in LinkedIn

THREE IN THE BED. "Progressive or sequential senescence occurs during vegetative growth in herbaceous species when continued leaf production at the stem apex is frequently at the expense of the senescence of preceding leaves on the shoot. For example, in certain temperate pasture grasses, each vegetative branch (tiller) generally carries about three mature leaves at any given time, and every new leaf that appears must be balanced by senescence of the lowermost leaf." https://lnkd.in/dPac2Jv View in LinkedIn