Factors influencing production of flower stalks in agropyron cristatum (L.) gaertn

• Main Author: Frischknecht, Neil C.
• Format: Others
• Published: BYU ScholarsArchive 1968
• Subjects: Agropyron cristatum (L.) gaertn
• Online Access: https://scholarsarchive.byu.edu/etd/8054; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=9054&context=etd

A study was made of factors that influence production of different numbers of flower stalks of crested wheatgrass on grazed and ungrazed areas. Both laboratory and field studies were made. Greatest response in flower stalk production resulted from application of nitrogen in the field, amounting to an increase of from 5 to 10 times the numbers of flower stalks on untreated areas. Responses of plants in the greenhouse supported these results. Plants grown in the dark indicated that higher carbohydrate reserves existed in ungrazed than in grazed plants. It was concluded that a high carbohydrate-low nitrogen balance was the primary factor in low production of flower stalks on ungrazed range. Removing photosynthetic tissue by grazing reduced the amount of root growth and amount of carbohydrates stored as reserves. On grazed range some stored carbohydrates are used in production of regrowth and new tillers giving a more favorable carbohydrate-nitrogen balance for production of flower stalks. Whether nitrogen is a primary or secondary factor in production of flower stalks depends upon the stage of plant development in which it is the limiting factor. Leachate from old growth showed no effect on production of flower stalks. Treatment with gibberellic acid suppressed flower stalk production on plants transferred to the greenhouse prior to beginning spring growth, and to a lesser extent on plants transferred after beginning spring growth. The effect was attributed primarily to the stimulation of rapid, increased growth and depletion of reserves required for differentiation and production of flower stalks. Plants produced increased numbers of flower stalks with exposure to outside cold temperatures at least up to 10 weeks' duration, which was the maximum period tested. Under field conditions, grazed plants would be subject to more rigorous temperatures than ungrazed plants, but this was believed to be a minor factor contributing to the greater numbers of flower stalks on grazed plants compared to carbohydrate-nitrogen relationships. Reduced light was shown to be a factor contributing to reduced numbers of flower stalks in the greenhouse and in an outside lath house. Reduced light was believed to be a minor factor, however, in contributing to the low numbers of flower stalks on ungrazed areas. Results of the present study indicate that the carbohydrate-nitrogen balance in plants is a better criterion for intensive management of range lands than carbohydrate reserves alone.