Factore Affecting Dormancy

Noelene Anne C. Aram

Exercise 4.

Seed Dormancy in Rottboellia cochinchinensis (formerly R. exaltata)

INTRODUCTION

During the life of plants including weeds, survival and reproduction is being maximized through functional traits such as dormancy (Dekker, 2011). As further cited by Dekker, seed dormancy refers to the state in which viable seeds or buds fail to germinate under favorable conditions (Amen, 1968). It is then evident that dormancy is one of the adaptations that plants developed to continue to proliferate and exist.

Commonly known as itchgrass, Rottboellia cochinchinensis (formerly R. exaltata), has brace roots near the base of the plant, a cylindrical spikelet seedhead and siliceous hairs on the leaf sheath that can irritate the skin (Sandoval et al, 2017). This grass is one of the problematic weeds commonly found in rice and corn fields.

Concepts of population biology including germination and dormancy are helpful tools to predict weed infestations better and to device a sustainable control (Bhowmik, 1997). It is then important to consider germination and dormancy and the factors affecting them. This experiment aimed to consider the different conditions that influence R. cochinchinensis, a weed known to exhibit dormancy. The specific objectives of the experiment were

1. To study the role of the husk or hull in the dormancy of Rottboellia seed.
2. To determine the effect of light and contact with the soil on the germination of Rottboellia.
3. To determine the interaction of the above factors on the germination of Rottboellia.

MATERIALS AND METHODS

In studying the dormancy of Rottboellia seeds, newly harvested seeds were prepared. In Petri dishes lined with moist filter paper or half-filled with soil, 25 dehulled and intact seeds were sown separately. The sown seeds were then exposed to different treatments: on filter paper subjected to diffused light in the laboratory, on filter paper subjected to artificial light from a light bank, on filter paper covered with used sheet of carbon paper, on soil exposed to diffused light in the laboratory, on soil exposed to artificial light from a light bank, and on soil covered with used sheet of carbon paper. Three replications were made for each treatment of dehulled and intact seeds. The percentage of germination one and two weeks after sowing were recorded.

RESULTS AND DISCUSSION

Table 1. Percent Germination of Intact and Dehulled Rottboellia cochinchinensis Seeds Under Different Conditions

Shown in table 1 is the percent germination of intact and dehulled seeds provided with different conditions. In treatments with intact seeds, regardless of the media used and light condition, no seeds have germinated after one week or after two weeks after sowing. In dehulled seeds, maximum percent germination of 60% was observed in soil exposed to artificial light. This was followed by the treatment exposed to diffused light with 53.33% in filter paper medium. In soil medium, diffused light and dark treatments both had a germination percentage of 40%. Treatment exposed to darkness with filter paper as medium had a 36.67% germination percentage. Least percent germination was observed in treatment exposed to artificial light with filter paper as medium.

There is no doubt that dehulling induces and increases the germination percentage which can be observed on the results. Based on a study on the seed dormancy and germination of Rottboellia, husk or hull removal increased the germination percentage of the seeds (Thomas and Allision, 2009). Another study on the biology and control of itchgrass supported that germination of intact and newly harvested seeds was increased by dehulling or treatment with GA (Jantawinyurag, 1995). 

Germination percentage was generally higher in treatments with soil as medium than those with filter paper although the only significant difference in germination percentage was observed evidently in the treatment exposed to artificial light.