Graduate Studies

 

First Advisor

John Lindquist

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Agronomy and Horticulture

Date of this Version

8-2024

Document Type

Dissertation

Citation

A dissertation presented to the faculty of the Graduate College of the University of Nebraska in partial fulfillment of requirements for the degree of Doctor of Philosophy

Major: Agronomy and Horticulture (Crop Physiology and production)

Under the supervision of Professor John Lindquist

Lincoln, Nebraska, August 2024

Comments

Copyright 2024, Hafith Furqoni. Used by permission

Abstract

Understanding the physiological basis of variation in seed composition is critical for optimizing soybean seed composition. Also, studying dry matter accumulation and nitrogen uptake, partitioning, and redistribution in soybeans is crucial due to its direct impact on seed yield levels and overall plant productivity. This study aimed to test the primary proxy influencing seed protein and oil content, which is their accumulation rate determined by the assimilate supply per seed. The second objective was to comprehensively understand soybean dry matter (DM) accumulation and nitrogen (N) uptake, partitioning, and removal patterns within the canopy. Field experiments were conducted using two soybean varieties, Hoegemeyer LL2841 (high-protein concentration) and Pioneer P27A17X (low-protein concentration), planted at early, mid, and late dates. The first study showed that at the whole plant level, protein and oil accumulation rates accounted for over 51% of the variation in seed component contents, with leaf area per seed at the R5.5 stage explaining more than 66%. However, within individual canopy strata, the relationship between assimilate supply and accumulation rates was less consistent. Protein accumulation rates significantly influenced protein content in strata 1, 3, and 4, while oil accumulation rates were significant only in strata 4 and 5. The second study indicated that whole plant accumulation of DM and N is minimal until approximately R1, then increases rapidly to the peak near R3 for all treatments. After R5, vegetative organs (leaves and petioles) generally began remobilizing DM and N to seed, whereas stems began DM and N remobilization at R6, possibly supporting greater DM remobilization to the seed. Within strata, peak accumulation of DM and N shifted from R1 to R7 from the bottom of the plant (strata 1) to the top (strata 5). Moreover, vegetative organs varied in their time of maximum DM or N accumulation, and when remobilization of DM or N to seed was initiated. Our results showed that at the whole plant level, seed N accumulation primarily relied on remobilization from vegetative organs rather than on continued uptake. Strata 2 and 3 contributed most of remobilized N to seed.

Advisor: John Lindquist

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