Rice seedlings

The toxin is less effective on oats and wheat and does not have the specificity reported for the toxin from Hehmnthosporium vic-toriae for oats. A metabolite isolated from another strain of H. sativum in Japan by Tamura et al. (15) has a marked elongation effect on the shoots of rice seedlings. The structure of this metabolite is closely related to that described here. 

T. Heulin, A. Gukert, and J. Balandreau, Stimulation of root exudation of rice seedlings by Azospirilluin strains carbon budget under gnotobiotic conditions. Biology and Fertility of Soils 4 9 (1987). 

Fig. 2 The effect of three phenolic acids on the Chi content of 2-week-old rice seedling. A. o-Hydroxyphenyl acetic acid B. ferulic acid and C. p-Coumaric acid. Kimura s culture solution contains 0, 25, 50, or 100 ppm of either o-hydroxyphenyl acetic, ferulic or p-coumaric acids. Extraction was done on liquid-nitrogen frozen leaves with 80% acetone. The data is mean of three determinations and the bars indicate the standard deviation (Yang et al. 2002, 2004).

Several secondary metabolites are dithiolanes, as for instance the allelochem-icals found in the tropical weed, Sphenoclea zeylanica. Zeylanoxide A is present in two stereoisomeric forms depending on whether the chirality at sulfur is (R) or (5) the latter form is 44 (Scheme 15). Zeylanoxides B are similar but in these cases the oxide function is on the sulfur at the 2 position. These molecules inhibited root growth in rice seedlings as well as the germination of letuce seeds.95... 

It causes 100% destruction of rice seedlings in the germinating stage and at least 20% destruction of rice seedlings in transplanted seedlings. 

The unharvested parts of rice plants are generally mixed with the soil because this has been thought to be beneficial. It has been observed however, that productivity of the second crop of rice in a paddy is less than that of the first crop. Chou and Lin (45) found that aqueous extracts of decomposing rice residues in soil retarded radicle growth of rice seedlings and growth of rice plants. Maximum toxicity occurred in the first month of decomposition and declined thereafter. Some toxicity persisted for four months in the paddies. Five inhibitory phenolic acids were identified from decaying rice residues and several unidentified allelochemicals were isolated. 

Scaglioni, L., A. Selva, L. Cattaruzza, and F. Menegus. Pantoyllactone pri-meveroside structure and its distribution with pantoyllactone glucoside in rice seedling organs. Nat Prod Lett 2000 14(3) 159-166. 

Islam, M. A., D. Mahalanabis, and N. Majid. Use of rice-based oral rehydra-tion solution in a large diarrhoea treatment centre in Bangladesh in-house production, use and relative cost. J Trop Med Hyg 1994 97(6) 341-346. Okai, Y., T. Eksttikul, O. Svendsby, M. Izukz, K. Ito, andN. Minamiura. Antitumor activity in an extract of Thai rice seedlings. J Ferment Bioeng 1993 76(5) 367-370. 

Kong C, Liang W, Xu X, Hu F, Wang P, Jiang Y. 2004. Release and activity of allelochemicals from allelopathic rice seedlings. J Agric Food Chem 52 2861-2865. 

Hirata, H., Hisaka, H. Hirata, A. (1982). Effects of phosphorus and potassium deficiency treatment on root secretion of wheat and rice seedlings. Soil Science and Plant Nutrition 28, 543-52. 

Ogawa, M. Ida, S. (1987) Biosynthesis of ferredoxin nitrite reductase in rice seedlings. Plant and Cell Physiology 28, 1501-8. 

Christie, P.J., Hahn, M. Walbot, W. (1991). Low temperature accumulation of alcohol dehydrogenase-1 mRNA and protein activity in maize and rice seedlings. Plant Physiology 95, 699-706. 

Kato-Noguchi, H., Ino, K. Rice seedlings release momilactone B into the environment. Phytochemistry 2003 63 551-554. 

---