Gibberellin‐induced elongation and osmoregulation in internodes of floating rice

Abstract

Internodal elongation in floating rice (Oryza sativa L. cv. Habiganj Aman II) is known to be enhanced by treatment with ethylene or gibberellic acid (GA3) at high relative humidity (RH). However, ethylene‐induced internodal elongation is inhibited at low RH. while GA3‐induced internodal elongation is hardly affected by humidity. We examined the possible involvement of osmoregulation in the stimulation by GA3 of the elongation of internodes at low RH. Submergence and treatment with ethylene or GA33 at 100% RH increased the osmotic potential in internodes of excised stem segments, while GA3 at 20% RH maintained the osmotic potential at a low level. In internodes of stem segments that had been treated with GA3 at 20% RH, the activity of invertase and the level of soluble sugars were almost 2‐ and 1.5‐fold higher, respectively, than those in internodes that had been treated with GA3 at 100% RH. These results indicate that one of the possible mechanisms by which GA3 promotes elongation of internodes at low RH involves the osmoregulation that is achieved by promotion of the synthesis of invertase.

Roles of gibberellins in increasing sink demand in Japanese pear fruit during rapid fruit growth

“…In contrast to what is known about the regulation of sucrose metabolizing enzymes by GAs in plant (Miyamoto et al 1993;Chen et al 1994;Azuma et al 1997;Dreier et al 1998), little information is available for GA-regulation of sorbitol-metabolizing enzymes. Since SDH exhibits significantly greater activity than SOX during the fruit enlargement phase, it has been proposed that SDH is important in sorbitol metabolism in apple and Japanese pear (Yamaki and Moriguchi 1988;Yamaguchi et al 1996;Yamada et al 2006).…”

“…Additionally, there is accumulating evidence that GAs play a significant role in regulating invertase levels which can, in most cases, be related to the increased carbohydrate demand of the rapidly growing tissues (Roitsch and Gonzalez 2004). As shown for other species (Miyamoto et al 1993;Azuma et al 1997;Dreier et al 1998), applied GA stimulated both Inv-CW and Inv-N activities in Japanese pear fruit (Figs. 5,6,7).…”

Molecular Events Underlying Coordinated Hormone Action in Submergence Escape Response of Deepwater Rice

“…Therefore, GA is considered to be the ultimate plant hormone that promotes elongation of deepwater rice internodes. GA 1 is also known to induce ethylene production in deepwater rice internodes (Azuma et al 1994), indicating synergistic interaction between ethylene and GA. Hormone interaction during submergence response has also been confirmed in the flooding-tolerant dicotyledonous model plant Rumex palustris (Voesenek et al 2003).…”

Determination of Endogenous Hormones Content in Cotton Varieties (Gossypiumhirsutum) as Influenced by Phosphorus and Potassium Nutrition

“…Auxin forms in the meristemic tissues of stem, root apices and in young developing leaves (Wareing & Phillips, 1970), root growth and development (Torrey, 1950;Blakely et al, 1982;Muday & Haworth, 1994;Casimiro et al, 2001;Jose et al, 2002). Gibberellic acid is an important hormone that regulates physiological activities in plant such as nutrients transport, inducing stem elongation, increase in dry matter production and weight, leaf area expansion and flowering (Wareing & Phillips, 1981;Brock, 1993;Azuma et al, 1997;Bhaskar et al, 1997;Gupta & Dutta, 2001;Takei et al, 2002;Khan & Samiullah, 2003;Shah et al, 2006). Cytokinins promote cell division and differentiation, stimulate photosynthesis (chlorophyll formation), flower production and senescence process (Hartman et al, 1981;Frankenberger & Arshad, 1995;Arshad & Frankenberger, 1998;Zahir et al, 2001).…”