Development of new peanut (Arachis hypogaea L.) cultivars over the past 40 years has more than doubled yield potential. The purpose of this paper is to identify and evaluate the physiological changes made in the course of this varietal improvement that are responsible for the great increase in yield potential. Weekly harvests of large samples of four Florida cultivars, a Spanish peanut type, and one soybean (Glycine max (L.) Merr.) cultlvar gave the information needed to show the progressive changes in dry weights of all plant parts throughout the growing season. Other weekly samplings and observations gave numbers of pegs, flowers, and fruits as well as fruit weights, root length, shoot length, and leaf areas. Quantitative estimates of the physiologlcal factors responsible for the dry weight differences were made by computer simulation using the PENUTZ model. Differences in three physiological processes explain most of the yield variation among the five peanut cultivars; the partitioning of assimilate between vegetative and reproductive parts, the length of the filling period, and the rate of fruit establishment. Of these, the partitioning of assimilate had the greatest effect on fruit yield. Estimates of partitioning to fruit ranged from 41% in the first cultivar released to 98% in the most recently released cultivar. Crop growth rates did not differ significantly among peanut cultivars but all were much higher than the crop growth rate of soybeans.
Potato (Solanum tuberosum L.) crop yield is the result of net crop dry matter assimilation (NDMA) and fraction of NDMA partitioned to tubers (α) integrated from the day of tuber initiation onset (TIO) through the day of tuber growth cessation (M). These four physiological yield parameters respond to environment and crop development by complex and poorly understood relationships. A crop growth and development model was constructed to determine the integrated temperature sensitivity of the four yield parameters and to test the hypothesis that temperature effects on α may be explained by growth temperature responses of different potato crop components. The crop was divided into three components, canopy, roots, and tubers. Model inputs were daily mean air temperature, soil temperature at 10 cm, solar radiation, and initialization parameters. Simulation began at emergence and continued through three developmental phases, canopy growth, tuber initiation, and tuber growth, which were demarked by four events, emergence, TIO, tuber initiation end, and M. Simulated TIO wau a function of temperature, whereas tuber initiation end and M were indirectly related to both temperature and radiation. Net crop dry matter assimilation was a direct function of incident solar radiation, canopy light interception, and tuber growth rate. Temperature affected NDMA indirectly through effects on canopy light interception and tuber growth rate. Assimilate partitioning was modeled as a function of available assimilates and empirically derived functions of the relationship between potential growth and temperature for each crop component. Potential growth of root and canopy had a 22 to 24°C optimum, whereas potential tuber growth had a 14 to 16°C optimum. Simulated leaf duration decreased as temperature increased. The model appropriately responded to temperature and solar radiation inputs to simulate cultivar Sebago growth in North Florida. In simulations, the most temperature sensitive yield parameter was TIO, with cool temperatures generally causing earlier TIO. Both M and NDMA were relatively insensitive to temperature with α having intermediate temperature sensitivity. Maximum simulated yield was at 15°C which corresponded with earliest TIO and maximum α. We conclude that temperatureffects on assimilate partitioning may be explained by differential temperature growth responses of potato crop components.
This experiment was conducted to test our hypothesis that the number of fruits established per plant should be inversely proportional to the growth rates of the individual fruits. Peanuts (Arachis hypogaea L.) were chosen as the test plant because their peculiar growth habit enabled us to vary fruit growth rates in a field experiment by cooling or warming the small soil volume occupied by the growing fruits with minimal effects on foliage and root temperatures.As predicted by the hypothesis, slower growth rates per fruit obtained by cooling the soil of the fruiting zone 4 C below the average ambient soil temperature of 27 C caused more fruits to be established. Warming the soil of the fruiting zone 3, 7, and 10 C above the ambient soil temperature had much less effect on fruit growth rates and consequently only the highest temperature caused a significant reduction in the number of fruits established. When harvest was delayed, as necessary to allow slower growing fruits to mature, average fruit weights were nearly the same for all except the warmest soil treatment. Thus the lower soil temperature resulted in a higher fruit yield because more fruits developed to nearly the same average weight but a longer filling period was required. The highest temperature produced the lowest yield because fewer and somewhat smaller fruits were produced.
Peanut (Arachis hypogaea L.) may have one or more periods during development when low solar radiation intensity is particularly detrimental to high yield. The present studies were conducted in the field to determine the effect of shade on vegetative growth, partitioning of assimilates and yield components of peanut. In a 2‐year experiment, 75% shade was applied for 7, 10, 14, or 21 day periods during flowering, pegging, podding, and maturing phases. The objective was to determine which reproductive phase was most sensitive to low solar radiation intensity. Flower number, peg development, pod formation, and dry matter accumulation and partitioning were measured at regular sampling intervals. Shade during the peak flowering period reduced the number of flowers per plant and inhibited peg formation. Shade during the pegging and podding phases reduced total peg and pod number and reduced pod dry weight. Shade during the maturing phase reduced seed fill as shown by reduced shelling percentage and a lower number of fruits achieving mature pod status. On the average, over all stages, 75% reduction of light intensity decreased the growth rate of vegetative parts by 85%, the reproductive growth rate by 67%, and the total biomass growth rate by 67%. Shade prior to podding increased partitioning to vegetative growth, by 20%, whereas shade during the podding phase (83 to 104 days) increased dry matter partitioning to pods by 127%. Seventy‐five percent reduction in solar radiation intensity reduced yield of Florunner peanuts significantly only when the duration was for 14 or 21 day periods. Podding was the phase in which yield was most sensitive to shade with a 30% reduction in fruit yield from shade during 83 to 104 days of age. The maturing phase was next in sensitivity to shade, which decreased yield primarily by decreasing seed fill in existing fruits. Twenty‐one days of shade at flowering did not reduce final fruit yield, since the plants had time to recover from the loss of active flowers and subsequently bear flowers and produce a normal pod load.
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