Relationship of Photoperiod and Nitrogen Nutrition to Initiation of Flower Primordia in Soybean Varieties

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Abstract
In a study of the effects of photo-period and N nutrition on the expression of certain morph. characteristics of soybean, plants of Morse, Virginia, Lincoln, and T-48 vars. were grown either in controlled environment rooms or in the greenhouse and in either soil or sand cultures. In expts. in which N nutrition was not a factor, all vars. flowered on all durations of photoperiod, but first-flower primordia were formed at a higher node on the plant axis with the longer photoperiods. Position of first-flower primordia did not vary with N treatment when the plants were grown with short photoperiods. When grown with long photo-periods, however, plants of certain vars. initiated first-flower primordia at higher nodes as the amt. of N in the nutrient soln. was increased. Var. T-48 was outstanding in this respect, Lincoln was intermediate, while Morse and Virginia were least responsive. Plants of Lincoln and Morse grown on long photoperiods showed no effect of N cone, on the number of nodes bearing flower primordia, while there was an effect with Virginia and T-48. The number of flower nodes increased with increasing N cone, in the case of Virginia, while the opposite trend was true for T-48. The total no. of nodes per plant increased with increasing N cone, when Lincoln, Morse, and Virginia were grown on photoperiods that delay flowering, while this was not true for plants of the T-48 var.