| I conducted a greenhouse study to determine the individual and combined effects of watering frequency and defoliation on plants from three populations of Buchloe dactyloides (Nutt.) Engelmann (buffalograss), collected from southern Wyoming to southeastern Colorado. The objectives of my study were: (1) to identify morphological and physiological differences among the three buffalograss populations, and (2) to determine the effects of watering frequency and defoliation and their interactions on morphology, biomass allocation and nitrogen status of buffalograss. Sods from these areas were maintained in the greenhouse for one and a half years. Staminate plants from these sods were then transplanted to individual pots for a multifactorial, randomized, complete block experiment. Water was supplied either every two days (frequent watering) or weekly (infrequent watering). Defoliation of one half the plants from each watering regime was done biweekly, and the experiment was terminated after eight weeks. I determined dry mass of aboveground parts and ash free dry mass of belowground parts and estimated percent nitrogen by the micro-Kjeldahl method.; The populations were significantly different for number of primary stolons per parent plant, average cumulative length of primary stolons connected in a linear series, number of tillers/parent plant, dry mass above ground, and mass per leaf. Infrequent watering reduced plant growth, but overall the effect was less than that of defoliation. Defoliated plants had a significantly greater number of stolons than nondefoliated plants. Infrequent watering and defoliation changed the plants' morphology by decreasing stolon number and average cumulative length of primary stolons connected in a linear series, only in one population. Infrequent watering also reduced the aboveground dry mass for two of the three populations. Defoliation reduced the total cumulative aboveground biomass (i.e., amount present on plants plus amount clipped off) by about 50% in all the three populations, but significantly reduced root biomass in only one population. However, defoliation increased the aboveground nitrogen concentration from about 1.4% in nondefoliated plants to 2.4% in defoliated plants but significantly reduced nitrogen use efficiency in all the populations. The morphological and physiological differences among the buffalograss populations in response to infrequent watering and defoliation may be the result of strong selection pressures caused by grazing or abiotic factors. |
