California experiment bins Left: August 16 – 1 st bin. 46 cm depth on right. Right: September 10 harvest date – 61 cm depth on left. Introduction: Some commercial wildrice (Zizania palustris) producers have observed that plants growing in deeper water develop larger seeds. Experiments were conducted in California and Minnesota to examine the influence of water depth upon wild rice plant development. Materials and Methods: California - Wildrice was grown in 11L pails containing of 12 kg of Dudgen-graven pale brown loam suspended in 120 cm lined steel tanks. The soil was amended with , zinc chelate, iron chelate, flooded on June 20, On June 24, 2005 Franklin wildrice seedlings at Wild Rice Growth Stage Scale (WRGSS) 03 were seeded at 283 seed/m 2 at 15, 30, 46, 61 and 76 cm depths in four replicate tanks. On September 10, 2005 before any shattering occurred, all heads with dark seed were harvested. Head length was recorded and seed larger than 1mm diameter was counted and measured for length. Plant height was measured at the harvest date. Minnesota - Franklin (same seed source as California) and Itasca at WRGSS 03 were transplanted on May 9, 2005 into preflooded soils in 11L pots (10-15 seedlings per pot) containing 9.3 kg of dry sandy loam topsoil previously amended with two 6-g planting tablets (14-4-6). Four replicates of pots were suspended in a single tank at 15, 30, 46, 61, and 76 cm depths. Pots were top dressed with urea at heading, equivalent to 55 kg/ha. At harvest, pedicels per panicle were counted, plant height measured from soil level to bottom of panicle, and seeds counted and weighed. Hulled seed length was estimated using WinSeedle Software (Regent Instruments, Quebec, Canada). Influence of Water Depth upon Plant Development, Yield and Seed Size of Modern Wildrice Cultivars D.B. Marcum and R.A. Porter University of California, Davis and University of Minnesota Results: California - The late plant date caused accelerated maturity resulting in mature grain 78 days from seeding. Seed on all primary and some secondary panicles was mature; we counted and measured only plump, dark seed >1mm in diameter. Although plant height above water declined with increased water depth, total plant height above the soil level increased with depth (Fig 1). No seedlings reached the surface from 76 cm, and only two of the four replicates at the 61 cm depth had plants. Panicle length was similar at 15, 30 and 46 cm depth, with smaller panicles at the 61 cm depth (Fig 2). The number of mature seed per panicle and total seed yield was reduced as depths increased from cm to cm. Minnesota - Midge damage during emergence affected plants in deeper pots, allowing only a few of the 46 cm depths and none of the deeper ones to survive. Pedicel number was not significantly different between depths, but was higher for Itasca than for Franklin (Fig 3). Plant height from soil level decreased significantly from 30 to 46 cm depth for Franklin, and increased from 15 to 30 cm depth for Itasca. Seed weight increased significantly from 15 to 30 cm depth for Itasca only. However, seed length increased significantly; for Franklin as depth increased from 30 to 46 cm and for Itasca as depth increased from 15 to 30 cm depth. Minnesota experiment bin Discussion: Seed length in both experiments increased with depth. Seed weight of Itasca, but not Franklin in Minnesota increased with depth. Fewer number of mature seed per panicle with Franklin in California suggests increased seed length and weight could be due to allocation of resources to fewer seed per panicle as depth increases. Although wildrice is known to easily emerge from depths greater than 46 cm, midge affected emergence in Minnesota in this experiment and we have no good explanation for poor emergence from 61 cm and no emergence from 76 cm depths in the California experiment.