Seed germination and seedling growth of the Mexican sunflower Tithonia diversifolia (Compositae) in Nigeria, Africa

We studied seed germination and seedling growth of the Mexican sunflower Tithonia diversifolia in Nigeria. This involved the usage of some dormancy-releasing methods and the effect of some concentrations of three herbicide formulations on the young seedlings. Initial germination tests on fresh and stored seeds revealed a low percentage germination of less than 30%. The seeds of the weed exhibit dormancy. Subjecting the seeds to wet heat at 80 and 100 degrees C and light treatment terminated dormancy both in the fresh and stored seeds. Light greatly enhanced the germination percentage of seeds by about 70%. There was gradual increase in germination percentage with increase in storage period in dormancy-released seeds. The mean LAR (Leaf Area Ratio), NAR (Net Assimilation Rate) and RGR (Relative Growth Rate) are comparatively high in young seedlings. Concentrations of 0.5-2.0% of Gramoxone, Primextra and Galex are toxic to 1 month old seedlings. For eradication, the seedlings should be attacked at one month stage.

Se estudió la germinación y crecimiento de las plántulas del girasol mexicano Tithonia diversifolia. Se usaron métodos de periodo de latencia y germinación, y el efecto de varias concentraciones de tres herbicidas sobre las plántulas jóvenes. Las pruebas iniciales de germinación con semillas frescas y almacenadas revelaron un bajo porcentaje de germinación (30%). Las semillas de malezas permanecieron latentes. Al someter las semillas a tratamientos de calor húmedo de 80 y 100oC y luz se terminó con el periodo de latencia en las semillas frescas y en las almacenadas. La luz aumentó el porcentaje de germinación a cerca del 70%. Hubo un incremento gradual en el porcentaje de germinación en el periodo de almacenamiento en las semillas salidas de la latencia. Los promedios de cociente de área foliar, tasa neta de asimilación y tasa de crecimiento relativo son comparativamente altos en las plántulas jóvenes. Las concentraciones de 0.5-2.0% de Gramoxone, Primextra y Galex son tóxicas para las plántulas de un mes de edad.

Seed germination and seedling growth of the Mexican sunflower Tithonia diversifolia (Compositae) in Nigeria, Africa.

We studied seed germination and seedling growth of the Mexican sunflower Tithonia diversifolia in Nigeria. This involved the usage of some dormancy-releasing methods and the effect of some concentrations of three herbicide formulations on the young seedlings. Initial germination tests on fresh and stored seeds revealed a low percentage germination of less than 30%. The seeds of the weed exhibit dormancy. Subjecting the seeds to wet heat at 80 and 100 degrees C and light treatment terminated dormancy both in the fresh and stored seeds. Light greatly enhanced the germination percentage of seeds by about 70%. There was gradual increase in germination percentage with increase in storage period in dormancy-released seeds. The mean LAR (Leaf Area Ratio), NAR (Net Assimilation Rate) and RGR (Relative Growth Rate) are comparatively high in young seedlings. Concentrations of 0.5-2.0% of Gramoxone, Primextra and Galex are toxic to 1 month old seedlings. For eradication, the seedlings should be attacked at one month stage.

Responses of some Nigerian vegetables of plant growth regulator treatments.

The effects of single and combined growth regulator treatments of indole-3-acetic acid (IAA), gibberellic acid (GA3) and coconut milk on plant height, yield, chlorophyll and vitamin contents of Abelmoschus esculetus L and Solanum gilo L were investigated. The single growth regulator treatments consisted of 50mg/L, 100 mg/L of IAA and GA3 and 10%, 15% of coconut milk. In case of combined growth regulator treatments, the treatments were 100mg/L IAA + 100mg/L GA3, 100mg/L IAA + 15% coconut milk and 100mg/L GA3 + 15% coconut milk. Control vegetable plants were sprayed with water. Single treatments of 100mg/L IAA,100mg/L GA3. 10% and 15% coconut milk resulted in significantly increased plant height, chlorophyll contents and yield of A. esculentus, H. sabdariffa and S. gilo while only combined treatments of 100mg/L IAA + 10% coconut milk and 100mg/L GA3 + 15% coconut milk had such an effect on A. esculentus and S. gilo but not on H. sabdariffa. Moreover, singletreatments of 100mg/L GA3 and 15% coconut milk caused significantly higher vitamins A, B6 and C contents of treated plants whereas the combined treatments produced such an effect on only vitamin C contents of treated plants. Growth regulator treatments of 100mg/L GA3 and 15% coconut milk were consistently the best out of the entire growth regulator treatments tried with the treated plants having the greatest plant height, yield, chlorophyll and vitamin C contents.