Seed Persistence in the Field May Be Predicted by Laboratory-Controlled Aging

Abstract

Weed management is complicated by the presence of soil seed banks. The complexity of soil–seed interactions means that seed persistence in the field is often difficult to measure, let alone predict. Field trials, although accurate in their context, are time-consuming and expensive to conduct for individual species. Some ex situ techniques for estimating seed life expectancy have been proposed, but these fail to simulate the environmental complexity of the field. Also, it has been questioned whether techniques such as the controlled aging test (CAT) are useful indicators of field persistence. This study aimed to test the validity of the standard CAT (seed aging at 45 C and 60% relative humidity) in use at the Royal Botanic Gardens, Kew, U.K., for predicting field seed-persistence. Comparison of seed persistence and CAT data for 27 northwest European species suggested a significant positive correlation of 0.31. Subsequently, 13 species of emerging and common weeds of Queensland were assessed for their seed longevity using the CAT. The seed longevity data of these species in the CAT were linked with field seed-persistence data according to three broad seed-persistence categories: < 1 yr, 1 to 3 yr, and > 3 yr. We discuss the scope for using the CAT as a tool for rapid assignment of species to these categories. There is a need for further studies that compare predictions of seed persistence based on the CAT with seed persistence in the field for a larger range of species and environments.

The stimulating impact of elevated temperatures on growth and productivity of <i>Parthenium hysterophorus</i> L.

“…Higher temperature during seed development increases seed germinability in many species (Llorens et al 2008). According to Long et al (2008), warm temperature at the time of Parthenium seed production enables the seed once shed to persist in the soil for more than three years, whereas cool temperature permit survival for only 1 -3 years. Toh et al (2011) reported that increased temperature enhances growth of Parthenium, enlarges canopy size and structure and accelerates population growth rate because of the shortened life cycle, supported by Entz &Fowler (1991) in wheat and Pandey et al (2003) in Parthenium.…”

Soil type does not affect seed ageing when soil water potential and temperature are controlled

“…In a variation on the controlled ageing test used in Long et al (2008), seeds were aged in the laboratory to accelerate ageing within a soil environment. Soils were collected from the field trial site and spread in a 10 to 20 mm layer in shallow plastic dishes that were sealed in boxes above a saturated KNO 3 solution, which created an atmosphere of 94.6% RH at 20°C.…”

Yellow bristle grass (Setaria pumila) germination biology

“…The decline in germination observed during the controlledageing test indicated the seed should be short lived, i.e. survives less than 3 years in the environment (Long et al 2008;; our model estimated a P 90 of 13.3 days. In other words, 10% of seed is likely to continue to persist in the environment for longer.…”

“…Following the comprehensive study performed by Long et al (2008), the CAT P 50 value may be converted into a rough prediction of field persistence. Species with low CAT P 50 (1-10) values tended to have relatively short seed persistence, those with higher P 50 values (>10) had longer persistence.…”