Teresa Fonseca, a collaborator in the ForChange group at the Forest Research Centre (CEF), together with scientists Ana Carvalho (CITAB-UTAD) – first author of the study – Inês Margarida Lopes (UTAD), Stéphanie Ribeiro (UTAD) and José Lima-Brito (CITAB-UTAD), have published a new paper analyzing the impact of recurrent fire and water stress on the nucleolar activity of Pinus pinaster roots.
The nucleolus, primarily responsible for ribosomal biogenesis, also responds to stress through changes in number, area, and morphology. Nucleoli with transcriptionally active ribosomal RNA genes stain positively with silver nitrate. This study analyzed nucleolar parameters in Pinus pinaster roots after germination of seeds collected in post-fire stands naturally regenerated stands. The analysed maritime pine individuals constituted descendants of trees located in stands with different fire regimes (burnt once, twice or three times).
To analyse the effect of fire recurrence in the nucleolar activity, seeds were germinated in distilled water. In addition, to verify the impact of both factors fire recurrence and PEG-induced water stress (WS) in the nucloelar activity, the P. pinaster seeds germinated in the presence of 10% PEG (moderate WS) and 20% PEG (extreme WS) solutions. Seeds collected from an unburned stand were used as a control. The nucleoli number per nucleus ranged from 1 to 15, with a common mode of 5–6.
Fire recurrence increased the nucleoli number (p<0.001), while both fire recurrence and PEG-induced water stress reduced them, particularly in the descendants of trees belonging to the stand that burned three times. Nucleolar area decreased with rising nucleoli numbers, fire recurrence, and PEG concentration (p < 0.001). These factors may affect protein synthesis and cell cycle regularity, which are fundamental for root growth, namely in dry soils.
Nucleolar parameters were proposed as suitable biomarkers for pine stress studies under the context of climate change since the projected climate scenarios have an increased frequency and severity of wildfire and drought episodes.
The article “Impact of Fire Recurrence and Water Stress on the Root Nucleolar Activity of Maritime Pine (Pinus pinaster Ait.) Individuals Whose Seeds Were Harvested in Post-Fire Naturally Regenerated Stands” was published in the special Post-fire Effects on Environment issue of Fire magazine and can be consulted at mdpi.com.