Sink strength: Established and regulated by plant growth regulators

Abstract

Sink strength or sink activity is considered here to be the rate of uptake of source-derived organic compounds and can be expressed in terms of the amount of sink-directed assimilates as a percentage of the total of newly produced assimilates. I emphasize that many studies on sink activity actually deal with sink capacity; care is needed to avoid confusion. Plants growing at more or less optimal conditions perform a pattern of dry matter distribution which is determined by their genetic background, experiences from younger growth stages and their present environment. Changes in the number of sinks and their intensity of the individual sinks (sink strength) during plant life is imposed by the ontogenetic pattern and greatly influenced by environmental signals:(1) Many plants increase their stomatal resistance as a first response to a diminished nitrogen availability in the rhizosphere via cytokinin (CK) metabolism, followed by a reduction in leaf expansion rate. A temporary increase followed by a decrease in the relative growth rate (RGR) of the roots and a reduced RGR of the upper part of the plant occur long before a reduction of the photosynthetic rate is observed because of the lowered N-input. As a consequence of lower sink strength starch accumulates in source and storage components of the plant. (2) Detached rose petals show an age-dependent response to a certain sucrose flux. When premature the activity of the carbohydrate-cotransporter in petals is strongly influenced by light intensity.

Effect of Growth Retardant (CCC) and Growth Promoter (6-FAP) on Seedling Growth and Chlorophyll Content of Coleoptile Leaves in Pearl Millet (Pennisetum glaucum L.) Under Moisture Stress

“…plumule and radicle of embryo in pre-soaked seed treatments could change the direction of assimilate transport and synthesis of auxin, gibberellin and ethylene in shoot and root meristems inverting the source-sink relationship in favour of shoot growth (Kuiper, 1993;Sakakibara et al, 2006). Fast growing roots act as strong sink for food reserves and grow at the expense of shoot growth.…”

Combining Enhanced Root and Shoot Growth Reveals Cross Talk between Pathways That Control Plant Organ Size in Arabidopsis

“…Evidence supports a role in nutrient signaling to coordinate metabolic processes between sink and source tissues (Argueso et al, 2009). Moreover, cytokinins stimulate photosynthesis (Wareing et al, 1968) and are able to establish local metabolic sinks or enhance sink strength (Kuiper, 1993;Guivarc'h et al, 2002). The effect on sink strength has also been demonstrated in 35S-CKX1-overexpressing tobacco (Nicotiana tabacum) plants, in which decreased cytokinin levels reduced the sink strength of the shoot (Werner et al, 2008).…”

Stress-Induced Cytokinin Synthesis Increases Drought Tolerance through the Coordinated Regulation of Carbon and Nitrogen Assimilation in Rice

“…The ability of CKs to increase sink capacity has been associated with their role in growth, through the control of cell division (Kuiper, 1993;Werner et al, 2008), photosynthesis (Paul Figure 6. Protein stability and oxidation of wild-type (WT) and transgenic P SARK ::IPT rice plants.…”

“…Cytokinins (CKs) have been shown to regulate plant cell differentiation, leaf senescence, and other key developmental processes (Sakakibara, 2006). It has also been shown that CKs regulate assimilate partitioning (Ronzhina and Mokronosov, 1994), sink strength (Kuiper, 1993), and source/sink relationships (Roitsch, 1999). The localized expression in tobacco (Nicotiana tabacum) of a promoterless ISOPENTENYLTRANSFERASE (IPT), a gene encoding the enzyme that catalyzes the rate-limiting step in CK synthesis, enhanced the local sink strength and quickly mobilized nutrients to the tissues with elevated CK (Guivarc'h et al, 2002).…”