Directorate of Land Reclamation, Government of Punjab, Lahore, Pakistan.
Soil and Water Testing Laboratory for Research, Dera Ghazi Khan, Pakistan.
PLoS One. 2020 Dec 29;15(12):e0244059. doi: 10.1371/journal.pone.0244059. eCollection 2020.
Numerous cropping systems of the world are experiencing the emergence of new weed species in response to conservation agriculture. Conyza stricta Willd. is being a newly emerging weed of barley-based cropping systems in response to conservational tillage practices. Seed germination ecology of four populations (irrigated, rainfed, abandoned and ruderal habitats) was studied in laboratory and greenhouse experiments. The presence/absence of seed dormancy was inferred first, which indicated seeds were non-dormant. Seed germination was then recorded under various photoperiods, constant and alternating day/night temperatures, and pH, salinity and osmotic potential levels. Seedling emergence was observed from various seed burial depths. Seeds of all populations proved photoblastic and required 12-hour light/dark period for germination. Seeds of all populations germinated under 5-30°C constant temperature; however, peak germination was recorded under 17.22-18.11°C. Nonetheless, the highest germination was noted under 20/15°C alternating day/night temperature. Ruderal and irrigated populations better tolerated salinity and germinated under 0-500 mM salinity. Similarly, rainfed population proved more tolerant to osmotic potential than other populations. Seeds of all populations required neutral pH for the highest germination, whereas decline was noted in germination under basic and alkaline pH. Seedling emergence was retarded for seeds buried >2 cm depth and no emergence was recorded from >4 cm depth. These results add valuable information towards our understanding of seed germination ecology of C. stricta. Seed germination ability of different populations under diverse environmental conditions suspects that the species can present severe challenges in future if not managed. Deep seed burial along with effective management of the emerging seedlings seems a pragmatic option to manage the species in cultivated fields. However, immediate management strategies are needed for rest of the habitats.
世界上许多种植系统都在经历新杂草物种的出现，这是对保护性农业的响应。Conyza stricta Willd. 是一种新出现的大麦种植系统杂草，对保护性耕作实践产生了响应。在实验室和温室实验中研究了四个种群（灌溉、雨养、废弃和野生栖息地）的种子萌发生态。首先推断种子是否存在休眠，这表明种子是非休眠的。然后在不同的光周期、恒定和交替的日夜温度以及 pH 值、盐度和渗透压水平下记录种子萌发。观察了各种种子埋藏深度的幼苗出土情况。所有种群的种子都证明是光敏感的，需要 12 小时的光/暗周期才能萌发。所有种群的种子在 5-30°C 的恒定温度下都能萌发；然而，在 17.22-18.11°C 下记录到峰值萌发。尽管如此，在 20/15°C 的昼夜交替温度下，萌发率最高。野生和灌溉种群对盐度的耐受性更好，在 0-500mM 盐度下萌发。同样，雨养种群对渗透压的耐受性强于其他种群。所有种群的种子在中性 pH 值下萌发率最高，而在碱性和碱性 pH 值下萌发率下降。种子埋藏深度大于 2 厘米会延迟幼苗出土，大于 4 厘米则不会出土。这些结果为我们了解 C. stricta 的种子萌发生态学提供了有价值的信息。不同种群在不同环境条件下的种子萌发能力表明，如果不加以管理，该物种在未来可能会带来严重的挑战。深播种子并有效管理出土幼苗似乎是在耕作地管理该物种的一种实用选择。然而，其他栖息地需要立即采取管理策略。
