Type-A Arabidopsis (Arabidopsis thaliana) response regulators (ARRs) are a family of 10 genes that are rapidly induced by cytokinin and are highly similar to bacterial two-component response regulators. We have isolated T-DNA insertions in six of the type-A ARRs and constructed multiple insertional mutants, including the arr3,4,5,6,8,9 hextuple mutant. Single arr mutants were indistinguishable ...

The aim of this study was to investigate the interactions between cytokinin, sugar repression, and light in the senescence-related decline in photosynthetic enzymes of leaves. In transgenic tobacco (Nicotiana tabacum) plants that induce the production of cytokinin in senescing tissue, the age-dependent decline in NADH-dependent hydroxypyruvate reductase (HPR), ribulose-1,5-bisphosphate carboxyl...

Two-component signaling elements play important roles in plants, including a central role in cytokinin signaling. We characterized two-component elements from the monocot rice (Oryza sativa) using several complementary approaches. Phylogenetic analysis reveals relatively simple orthologous relationships among the histidine kinases in rice and Arabidopsis (Arabidopsis thaliana). In contrast, the...

The possible relationship of branching habit to cytokinin content of apple shoots (Malus domestica Borkh.) was investigated. One-year old apple shoots are acrotonic (distal branching), more strongly so in Granny Smith than in Braeburn. In the ®rst trial, long, 1-year old Granny Smith and Braeburn apple shoots were sprayed on 29 August 1995 to break rest with dinitro-o-cresol (DNOC) oil (5%). Th...

Sumarry. In wheat seedlings (Triticum durum), uptake of potassium and nitrate, transpiration and shoot growth were inhibited by adding cadmium to the nutrient medium. A sharp reduction in cytokinin content was observed within two hours of supplying cadmium. The reduction in cytokinin content was probably a result of hormone breakdown. In support of this, Cd-treatment elevated cytokinin oxidase ...

Cytokinins are key regulators of a large number of processes in plant development, which is highly plastic and adaptive, and remarkably resilient and self-perpetuating. Cytokinin signaling involves a multistep two-component system, also called a phosphorelay signaling system. Genes encoding the central components to build the cytokinin phosphorelay system are found in diverse plant species, res...

this research was conducted at the agricultural college of tehran university in 2005 to analyze the effect of use of cytokinin as well as of calcium on durability of rose (illona cultivar). cuttings were taken from rose biennial mother plants, then treated by cytokinin of 0, 0.1, 1and10 micromole per liter and calcium of 0,10,20 and 30 milimole per liter. cut flowers, after harvest, were kept i...

Legumes develop different types of lateral organs from their primary root, lateral roots and nodules, the latter depending on a symbiotic interaction with Sinorhizobium meliloti. Phytohormones have been shown to function in the control of these organogeneses. However, related signaling pathways have not been identified in legumes. We cloned and characterized the expression of Medicago truncatul...

Cytokinins and gibberellins (GAs) play antagonistic roles in regulating reproductive meristem activity. Cytokinins have positive effects on meristem activity and maintenance. During inflorescence meristem development, cytokinin biosynthesis is activated via a KNOX-mediated pathway. Increased cytokinin activity leads to higher grain number, whereas GAs negatively affect meristem activity. The GA...

The plant root system is important for the uptake of water and nutrients and the anchoring of plants in the soil. Lateral roots (LRs) contribute considerably to root system architecture. Their post-embryonic formation is regulated by hormones and environmental cues. The hormone cytokinin influences LR formation and growth in Arabidopsis thaliana on different levels by disturbing cell division a...