Female flowering and acorn development in three species of white oaks were

Most perennial plants undergo annuLal eyeles of activity but forage plants, as a result of periodic defoliation, are compelled to undergo several cycles in one year. Much experimental work has been conducted to determine the yield, chemical composition, and in some eases the nutritive value of top growth removed by successive cuttings or grazings. The (growth processes of the plant during these periods have received only limited attention so that changyes that occur between two successive cuttings in those parts of the plant other than the edible tops have been deduced from occasional and usually not continuous observations. As part of a series of experiments concerned primarily with the reserve carbohydrates of underground parts, some of the changes that took place in the stubble and roots of perennial ryegrass when the plants were defoliated have been described (4). In the present paper chemical analyses of orchard grass subjected to three successive cuttinos are reported. The objectives of this work were twofold: first, to follow the fluetuations of carbohydrate reserves of the stubble and roots when orchard grass is clipped periodieally and mainltained in a veoetative condition, and second, to note the effects of nitrooeni fertilization upon these changes. The results indicate that a evele of compositional chanoes recurs after each cutting. Experimental procedureThe plant material used in this experiment was obtained by vegetative propagation from a vigorous clone of orchard grass, Dactylis glomnerata L. Established plants of this clone were broken up to provide numerous vegetative tillers. All roots and old leaves were removed and the tillers were placed in tap water for several days. When new roots appeared, three tillers were planted in each of a number of 1-gallon glazed crocks. The potting soil consisted of two parts of Ilagerstown silty clay loam and one part of river bottom sand. Adequate moisture was applied and maintained throughout the experiment. The crocks were arranged on four parallel benches in one section of a greenhouse.

When the foliar portion of a grass plant is removed by a mower or by a grazing animal, the growth of new tissues is initiated to replace the parts removed. The rate with which the regeneration of new top growth proceeds and the total amount produced are of great importance in forage production. This rate of recovery and total yield, although dependent to a large extent upon external environmental factors, are also influenced considerably by the intensity and frequency of defoliation as determined by management practices. Evidence has been offered by many workers (5, 9,10, 11,21,23,24,26,29) that close and frequent clipping or grazing reduces the total yield of tops of forage plants.Associated with the ability of the plant to produce new growth after cutting is its chemical composition. Plants cut less frequently and less severely have a greater opportunity to synthesize and maintain reserve food materials which are available for the production of new growth than plants more severely grazed. That carbohydrates are important as reserve substances in pasture plant economy has been pointed out by earlier workers (1,4,7, 8,13,14,15,16,25,27,28).The specific carbohydrates which may be considered "reserves" that can be utilized by the plants for purposes of respiration and production of new tissues have not been definitely established. WEINMANN (27) considered that sugars and polysaccharides hydrolyzable by hot dilute HCl were lost from the tops of some South African grasses after the time of flowering and were largely recovered in the roots. In another contribution (28), the seasonal changes in the composition of roots were described as mainly due to translocation and storage. Sugars and starch (polysaccharides rendered soluble by saliva and hydrolyzed by HCl) were considered of importance but the results with total hydrolyzable polysaccharides were not conclusive and were not reported. In alfalfa, ALBERT (2), GRABER, et al. (8), and LEUKEI (13)

In a previous paper (12) it was reported that, when perennial ryegrass (Olium perennjj .) was partly defoliated, the remaining plant parts underwent a progressive loss in soluble carbohydrates, namely sugars and fructosan, for a period of several weeks. This loss from the stubble and roots accompanied a rapid formation of new tissue above ground. When new top growth had produced sufficient photosynthetic area to manufacture its own organic matter, storage of soluble carbohydrates took place. When the percentages of the constituents were plotted against time as the abscissa, the soluble carbohydrates displayed a typical U-shaped curve. Many factors undoubtedly influence the slope and extent of this curve and some of these are being investigated. The present report concerns the relationship of temperature to the composition of ryegrass after cutting.The earlier paper included a review of the literature pertinent to the subject of reserves. Since then, other reports concerned with the analyses of forage grasses have verified the fact that soluble carbohydrates and starch function as reserves. More complex carbohydrates and those more resistant to hydrolysis, are not so regarded. Some of these recent papers are by BENEDICT and BROWN (2), PHILLIPS and SMITH (9), MCILVANIE (8), and WEINMANN (13,14,15,16). A review by Weinmann covers the general subject of reserves in grasses (17).Reserves in grasses are closely connected with the resistance of the plants to high temperatures. JULANDER (6) showed that grasses withstood limited exposures to a temperature of 480 C (118.40 F) when they had been previously hardened to dry conditions and had not been severely clipped. Both of these last conditions were conducive to the accumulation of reserve carbohydrates. He also noted differences between species, Kentucky bluegrass dying sooner at this temperature than Bermuda grass and a number of range grasses. At lower temperatures, grasses will survive for longer periods. According to HARRISON (5), Kentucky bluegrass grew very little at a constant temperature of 1000 F after having been defoliated, and died

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