Differential effects of N-1-naphthylphthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) on auxin control of swelling of the shoots of Bryophyllum calycinum Salisb.

Abstract

The effects of N-1-naphthylphthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) on the swelling of the stem in intact and decapitated plants of Bryophyllum calycinum in relation to the interaction with auxin, indole-3-acetic acid (IAA), are described. NPA induced conspicuous local internode swelling only in the area of its application in intact plants and in the decapitated internode in the case of simultaneous application of IAA on the top of the internode. By contrast, TIBA applied to an internode of intact plants induced swelling along the entire internode above the treatment area, and similar results were obtained in the decapitated internode when TIBA was applied in the middle of the internode and IAA was applied onto the top of the internode. The differential effect of NPA and TIBA on stem swelling in B. calycinum is discussed in relation to their differential mode of action on auxin transport.

Mode of Action of 1-Naphthylphthalamic Acid in Conspicuous Local Stem Swelling of Succulent Plant, Bryophyllum calycinum: Relevance to the Aspects of Its Histological Observation and Comprehensive Analyses of Plant Hormones

“…As shown in Figure 1 , conspicuous local stem swelling induced by NPA was confirmed in the present study. NPA substantially induced conspicuous local stem swelling also in some other succulent plants, such as B. daigremontianum , K. tubiflora , and Sedum spectabile ( Figure 1 ) , but TIBA did not show that effect (see Saniewski et al [ 11 ]). This fact suggests that, differently from TIBA, NPA induces conspicuous local stem swelling as an unusual mode of action regarding some auxin-regulated process in succulent plants.…”

“…As described in the Introduction, we have reported that NPA induced conspicuous local stem swelling only at the site of its application in intact plants and in the decapitated internode of B. calycinum when IAA was applied simultaneously on the top of the internode [ 11 ]. It should be mentioned that such conspicuous local stem swelling was not induced by the application of TIBA [ 11 ] or HFCA (Saniewski et al [ 11 ], unpublished results). As shown in Figure 1 , conspicuous local stem swelling induced by NPA was confirmed in the present study.…”

“…NPA induced conspicuous local stem swelling in succulent plants. Unlike NPA, TIBA and morphactin (IT 3456, HFCA) application to the internode of intact Bryophyllum calycinum plants did not induce such conspicuous local swelling, while they induced slight swelling along the entire stem above the treated area ([ 11 ]; Saniewski et al, unpublished results). It is important to elucidate the mode of novel physiological action of NPA in conspicuous local stem swelling for stiffening of plants, food production, and its industry [ 12 , 13 ].…”

“…calycinum leaves [ 9 , 10 ]. We also found that NPA induced conspicuous local stem swelling only in the area of its application in intact plants of B. calycinum , and in the decapitated ones when IAA was applied simultaneously on the top of the internode [ 11 ].…”

“…In contrast, the application of TIBA [ 11 ] and HFCA (Saniewski et al [ 11 ], unpublished results) in the same manner to B. calycinum plants did not induce conspicuous local stem swelling, whereas slight swelling along the entire internode above the treatment area was observed. These results suggest that the mode of actions of NPA is different from that of TIBA and HFCA in species of the family Crassulaceae, and that stem swelling in B. calycinum is caused by the interaction with NPA and IAA.…”