Diverse Promotive Action of Pyridinecarboxylic Acids on Flowering in Ornamentals and Seedling Growth in Vegetable Crops

This chapter describes our recent findings on diverse biological effects of pyridinecarbox - ylic acids, both pyridine- di -carboxylic acids (PDCAs) and pyridine- mono -carboxylic acids (PCAs), on plant growth processes. PDCA analogs promoted flowering and extended dis - play time (vase life) of cut flowers of spray-type carnation. 2,3-PDCA and 2,4-PDCA were most active in the promotion. Apart from these actions, some of PDCAs and PCAs stimu - lated root and shoot growth of lettuce, carrot, and rice seedlings. Studies on structure– activity relationship of the chemicals showed that one of the most effective chemicals was pyridine-3-carboxylic acid. Pyridine-3-carboxylic acid is known as vitamin B3 (niacin) and safe for human and animals. These findings suggested the possibility to develop PDCAs and PCAs as novel flower-care agents as well as growth-promoting agents which will be used for vegetable cultivation. inhibited it in lettuce, carrot, and rice seedlings. We explored the promoting activities of 2,3-PDCA to other PDCA analogs and pyridine-mono-carboxylic acid (PCA) analogs. Also, we carried out a preliminary investigation on the possible biochemical and molecular mechanism of PDCA, mainly with 2,4-PDCA. This chapter describes the details of the effects of 2,4-PDCA and related chemicals on flower opening and display time in carna tion flowers, as well as the promotion of seedling growth in some agricultural crops. GA GA GA 3 in petals of opening flowers Os 2 reached Os 4–6 in 4 days in the control flowers. treatment accelerated flower opening, and all the treated flowers reached Os 4–6 in 2 days. We measured GA 3 content in the non-treated flowers at days 0–4 and found that the GA 3 level tended to be decreased in the course of flower opening. We also measured GA 3 content in 2,4-PDCA-treated flowers at day 1, when the treated flowers showed a significant increase in the number of open flowers. We observed a tendency that GA 3 content in the 2,4-PDCA-treated flowers was lower than that in the control. The GA 3 content in the control flowers was 48.5 ± 10.0 pmol·g −1 FW, whereas it was 26.6 ± 14.3 pmol·g −1 FW in the 2,4-PDCA-treated flowers. There was no significant difference between the control and the treated samples by t -test at P < 0.05. These results showed 2,4-PDCA increases the gene expression of the growth suppressor, GAI, and decreases the GA level, suggesting that GA signaling and action are altered by 2,4-PDCA treatment. such changes are contradictory to the enhancement of flower opening, which that 2,4-PDCA