FACTORS AFFECTING SEED GERMINATION, SEEDLING EMERGENCE, AND SURVIVAL OF TEXASWEED (CAPERONIA PALUSTRIS)

Authors: Koger Iii, Clifford; Reddy, Krishna; POSTON, D - DELTA RES & EXT CTR

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2004
Publication Date: 10/1/2004
Citation: Koger Iii, C.H., Reddy, K.N., Poston, D.H. 2004. Factors affecting seed germination, seedling emergence, and survival of texasweed (caperonia palustris). Weed Science 18:1058-1065.

Interpretive Summary: Texasweed is a summer-annual broadleaf species that has become a problematic weed in rice and soybean grown in the lower Mississippi River Delta Region. Little is known about the effects of environmental and soil conditions common to soybean and rice on Texasweed seed germination and seedling emergence and survival. Studies were conducted at the Southern Weed Science Research Unit, Stoneville, MS to characterize Texasweed seed production, and determine the effects of light, temperature, planting depth, pH, osmotic and salt stress, and flood depth and duration on seed germination and seedling survival. Texasweed plants produced an average of 893 seed per plant. Seed exhibit dormancy and prechilling did not release dormancy. Texasweed seed germinated under light and dark conditions at temperatures ranging from 20 to 40 C, and under a broad range of pH, osmotic potential, and salt concentrations. Seedlings emerged from soil depths as deep as 7.5 cm. Seed did not germinate under saturated or flooded conditions, but survived flooding and germinated after flood removal. These results are important because they show that Texasweed is able to germinate under a wide array of environmental and soil conditions common to rice and soybean production systems, and that management options other than flooding must be considered.

Technical Abstract: Field, laboratory and greenhouse experiments were conducted to determine the seed production potential and effect of environmental factors on germination, emergence, and survival of Texasweed. Texasweed produced an average of 893 seed per plant and 90% were viable. Seed exhibited dormancy and prechilling did not release dormancy. Percent germination ranged from 56% for seed subjected to no prechilling to 1% for seed prechilled at 5 C for 140 d. Seed remained viable during extended prechilling conditions, with 80% of seed being viable even after 140 d of prechilling. Texasweed seed germinated over a range of 20 to 40 C temperatures, with optimum germination (54%) occurring with a fluctuating 40/30 C temperature regime. Seed germinated under fluctuating 12-h light/dark and constant dark conditions. High seed germination was recorded with a broad range of pH, osmotic potential, and salt concentrations. Seed germination was 31 to 62% over a pH range from 4 to 10. Germination of Texasweed ranged from 56 to 9% as osmotic potential increased from 0 (distilled water) to 0.8 MPa. Germination was greater than 52% at less than 40 mM NaCl concentrations and lowest (27%) at 160 mM NaCl. Texasweed seedlings can emerge from a 7.5 cm soil depth (7% emergence), but emergence was greater than 67% for seed placed on the soil surface or at a depth of 1 cm. Texasweed seed did not germinate under saturated or flooded conditions, but seed survived flooding and germinated (23 to 25%) after flood removal. Texasweed seedlings of 2.5 to 15 cm tall were not affected by a 10-cm-deep flood duration of up to 14 d. These results suggest that Texasweed seed is capable of germinating and surviving in a variety of climatic and edaphic conditions, and that flooding is not a viable management option for emerged plants of Texasweed.