Weed Seed Germination Temperature

Crassocephalum crepidioides, Conyza canadensis, and Ageratum conyzoides are alien annuals naturalized in China, which produce a large number of viable seeds every year. They widely grow in Xishuangbanna, becoming troublesome weeds that compete with crops for water and nutrients. As seed germination … JSTOR is a digital library of academic journals, books, and primary sources. JSTOR is a digital library of academic journals, books, and primary sources.

Seed germination response to high temperature and water stress in three invasive Asteraceae weeds from Xishuangbanna, SW China

Crassocephalum crepidioides, Conyza canadensis, and Ageratum conyzoides are alien annuals naturalized in China, which produce a large number of viable seeds every year. They widely grow in Xishuangbanna, becoming troublesome weeds that compete with crops for water and nutrients. As seed germination is among the most important life-stages which contribute to plant distribution and invasiveness, its adaptation to temperature and water stress were investigated in these three species. Results showed that: (1) These three species have wide temperature ranges to allow seed germination, i.e., high germination and seedling percentages were achieved between 15°C and 30°C, but germination was seriously inhibited at 35°C; only A. conyzoides demonstrated relative preference for warmer temperatures with approximately 25% germination and seedling percentage at 35°C; (2) light was a vital germination prerequisite for C. crepidioides and A. conyzoides, whereas most C. canadensis seeds germinated in full darkness; (3) Although all three species have good adaptation to bare ground habitat characterized by high temperatures and water stress, including their tolerance to soil surface temperatures of 70°C in air-dried seeds, A. conyzoides seeds exhibited higher tolerance to both continuous and daily periodic high-temperature treatment at 40°C, and to water restriction (e.g., ca. 65% seeds germinated to -0.8 MPa created by NaCl), which is consistent with their field behavior in Xishuangbanna. This study suggests that seed high-temperature tolerance contributes to the weed attributes of these three species, and that adaptation to local micro-habitats is a critical determinant for invasiveness of an alien plant.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1. Changes in seed germination as…

Fig 1. Changes in seed germination as affected by incubation temperatures and light.

a. Crassocephalum crepidioides; b. Conyza candensis; c. Ageratum conyzoides. Seeds sown on 1% agar were incubated at constant temperature from 10°C to 40°C, and at 18/28°C, with periodic illumination (light) or under full dark (dark). Germination and seedling percentages are expressed as means±SE of six replicates of 50 seeds.

Fig 2. Changes in viability of air-dried…

Fig 2. Changes in viability of air-dried (dry) and imbibed (wet) seeds as affected by…

Fig 2. Changes in viability of air-dried (dry) and imbibed (wet) seeds as affected by 30-min heat shocks at temperatures from 30°C to 95°C.

a. Crassocephalum crepidioides: b. Conyza candensis; c. Ageratum conyzoides. Survival and seedling percentages are expressed as means±SE of six replicates of 50 seeds.

Fig 3. Changes in seed viability as…

Fig 3. Changes in seed viability as affected by continuous high-temperature stress.

a. Crassocephalum crepidioides; b. Conyza candensis; c. Ageratum conyzoides. Seeds sown on 1% agar were subjected to heat shock at 40°C for indicated durations, and incubated at 25°C after they were released from stress. Survival and seedling percentages are expressed as means±SE of six replicates of 50 seeds.

Fig 4. Changes in seed germination as…

Fig 4. Changes in seed germination as affected by daily periodic high-temperature stress.

a. Crassocephalum crepidioides; b. Conyza candensis; c. Ageratum conyzoides. Seeds sown on 1% agar were subjected to 40°C and 25°C (h/h) alternately. Germination and seedling percentages are expressed as means±SE of six replicates of 50 seeds.

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Fig 5. Changes in seed germination as…

Fig 5. Changes in seed germination as affected by water potentials.

a. Crassocephalum crepidioides; b. Conyza candensis; c. Ageratum conyzoides. Seeds were incubated at 25°C on filter papers moistened with osmotic solutions. Water potentials were created by PEG 8000 and NaCl. Germination and seedling percentages are expressed as means±SE of six replicates of 50 seeds.

Fig 6. Changes in seed germination as…

Fig 6. Changes in seed germination as affected by imbibition-dehydration treatment.

a. Crassocephalum crepidioides; b. Conyza candensis; c. Ageratum conyzoides. After imbibition for the indicated period of time, seeds were dried for 72 h under 50% RH at 15°C, and then germinated for viability assessment. Seedling and germination or survival percentages, expressed as means±SE of six replicates of 50 seeds, were used to score germination before and after drying treatment, separately.

Weed Seed Germination Temperature

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Weed Seed Germination Temperature

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Block Reference: #76f5cfb7-1496-11ed-aabb-6e534a777653
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IP: 195.2.73.67
Date and time: Fri, 05 Aug 2022 08:13:19 GMT

©2000- ITHAKA. All Rights Reserved. JSTOR®, the JSTOR logo, JPASS®, and ITHAKA® are registered trademarks of ITHAKA.