Gibberellic Acid-Enhanced Synthesis and Excretion of Phosphatase lsozymes by Embryoless Rice Seeds

O arroz é uma das espécies que apresenta dormência após a colheita, podendo esta ser prolongada durante o armazenamento das sementes. Este trabalho teve por objetivo determinar se o ácido giberélico (GA3) é um promotor eficiente da superação de dormência em sementes de arroz e avaliar mudanças nas estruturas biológicas via histoquímica. A cultivar utilizada foi a SCS122 Miura submetida a 0 mg L-1, 500 mg L-1 e 1000 mg L-1 de GA3. Foram realizadas análises de germinação, viabilidade, comprimento de raiz, parte aérea e plântula, microscopia óptica do amido e quantificação dos açúcares solúveis totais. A utilização de 500 mg L-1 e 1000 mg L-1 de GA3 foi eficiente para a superação da dormência de sementes de arroz, reduzindo o percentual de sementes dormentes para 4% e 1% respectivamente. Apesar de reduzir o percentual dormência, a presença de GA3 provoca aumento do percentual de plântulas anormais, e por isso, nas concentrações utilizadas, não pode ser recomendado como método de superação em sementes de arroz. A microscopia óptica é eficiente para verificar que com a superação de dormência, ocorre a degradação dos grânulos de amido, aumentando a disponibilidade de açúcares solúveis totais para o crescimento e desenvolvimento de plântulas.

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Viability and Dormancy of Rice Seeds after Storage and Pre-Treatment with Dry Heat and Chemical Agents

Journal of Agricultural Science ◽

10.5539/jas.v9n7p175 ◽

2017 ◽

Vol 9 (7) ◽

pp. 175 ◽

Cited By ~ 2

Author(s):

Yvonne A. Mutinda ◽

James W. Muthomi ◽

John M. Kimani ◽

George N. Cheminigw’wa ◽

Florence M. Olubayo

Keyword(s):

Gibberellic Acid ◽

Seed Dormancy ◽

Seed Treatment ◽

Room Temperature ◽

Seed Quality ◽

Packaging Material ◽

Rice Seed ◽

Dry Heat ◽

Rice Seeds ◽

Pre Treatment

Inappropriate seed packaging and seed dormancy affects seed quality and consequently leads to reduced crop stand, low seedling vigour and reduced yields. The objective of the study was to determine the effect of seed packaging material and seed treatment on viability and dormancy in rice seeds. Effect of packaging material was evaluated by storing freshly harvested seeds of Basmati 370 and BW 196 varieties in polythene, khaki, cheese cloth, polypropylene (Pp) sack and gunny bag sat room temperature and at 6 oC for six months. Effect of seed treatment on dormancy was determined by pre-treatment of seeds with nitric acid at 0.1 M, 0.2 M, 0.5 M, 1 M and 2 M, gibberellic acid (GA3) at 1000 ppm, 2000 ppm and 5000 ppm, and hydrogen peroxide at 0.5 M, 1 M, 2 M, 3 M, 5 M and dry heat at 50 oC for 48 hours. The seeds were subjected to germination test on moist paper and data on percentage germination, seedling length and seedling dry weight were taken. Packaging material had a significant (P ≤ 0.05) effect on germination and vigour. At room temperature, seed stored in polythene bag had the highest germination 88.2% and 57.8% for BW 196 and Basmati 370, respectively. Basmati 370 in khaki bag stored in the cold room had the highest germination 48.3%, while BW 196 stored in polythene had the highest (86.0%). Pre-treatment of seeds reduced dormancy, with variety BW 196 showing the highest germination of up to 67%, while variety Basmati 370 had the lowest germination of up to 40%. Gibberellic acid (GA3) at 5000 ppm was the most effective in breaking seed dormancy resulting in up to 95.7% germination. The results of the study indicated that packaging rice seed in polythene bags for periods not exceeding six months and pre-treatment with GA3 maintains high seed viability and breaks dormancy, respectively, thus ensuring rapid and uniform germination of vigorous seedlings. This would reduce the period farmers have to wait after harvest before they can plant newly harvested rice seeds.

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