The history of Hyparrhenia hirta and studies of its flowering habits and seed production
1950
Hyparrhenia hirta is indigenous to the tropical and subtropical bunch-grass savannas of South Africa and Venezuela. It was introduced into the United States in 1905. Most authorities in North America have not considered this grass a valuable forage plant. Some workers, however, have found Hyparrhenia hirta well adapted to certain areas in Texas. Monthly mean weather data--temperature, humidity, rainfall, clear days, and cloudy days--accumulated at College Station in 1946 and 1947 indicated a clearer and drier period for anthesis in 1946 than 1947. A significant positive correlation in seed set was found between the same plants harvested each year, indicating that individual plants may produce a proportionately high or low number of caryopses from year to year. Observations on anthesis indicated that most flowering occurred during periods of decreasing temperature with increasing humidity, and increasing temperature with decreasing humidity. This was found to be soon after sundown and before sunrise. Spikelets near the center of the inflorescence tended to bloom first, but it was not unusual to find florets near the apex opening first. The lower and terminal florets generally opened last. Apparently the anthers dehisce soon after anthesis and the shedding of pollen seems to depend upon movement of the inflorescence. From a study of 88 plants it was found that a high degree of variation existed among plants in their ability to set seed. A highly significant positive correlation was found between the amount of seed setting and germination. Such evidence might be used for plant selection in this and other species where there is a relation such as the one presented in this study.
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