Recovery of Norway spruce (Picea abies) seedlings from repeated drought as affected by boron nutrition

Abstract

The effects of two boron (B) levels on growth, shoot water potential, gas exchange and nutrient accumulation in Norway spruce [Picea abies (L.) Karst.] seedlings were studied in a growth room experiment lasting 22 weeks which included well-watered control seedlings and seedlings exposed to one (8 days) or two (6+8 days) periods of drought and a rewatering period (8 days) at the end of the experiment. The effects of B and drought were monitored during drought and recovery. Needle B concentrations were 6 mg kg −1 (−B treatment) and 34 mg kg −1 (+B treatment) at the end of the experiment. The −B seedlings showed visible symptoms of damage in the upper shoot after repeated drought and had reduced height growth, root dry mass, allocation of biomass to roots and formation of root tips and mycorrhizas and reduced needle P, Ca, and Mg concentrations and contents. In contrast, 15 N uptake, shoot water potential and gas exchange were not markedly affected by B. It can be concluded that the visible symptoms of damage at low B were probably related to reduced B transport due to repeated drought. In contrast, the effects of low B on growth, particularly of the roots, and on nutrient uptake can be regarded as early effects which occur before any influence on shoot water potential or gas exchange. The positive effects of B on root biomass and nutrient accumulation are of particular importance regarding the establishment of young seedlings in the field.

Nutritional Efficiency of Eucalyptus Clones Under Water Stress

“…However, the role of B in increasing drought tolerance has also been observed in different species (Möttönen et al, 2005;Hodecker et al, 2014;Pita-Barbosa et al, 2016). Our previous studies confirmed the great influence of B on the increase of root growth and water use efficiency in Eucalyptus urophylla (Hodecker et al, 2014).…”

“…Similarly, to other nutrients, the importance of Ca and/or B for drought tolerance of plants has been shown in several studies (Möttönen et al, 2005;Hassan et al, 2011;Barros Filho, 2014;Hodecker et al, 2014;Pita-Barbosa et al, 2016). For clone PL040, although efficient in Ca and B use under sufficient water supply, AE and UE were strongly affected under drought stress, compared to the other genotypes.…”

Boron in forest trees and forest ecosystems

“…In Norway spruce seedlings, a relatively mild drought treatment increased root B concentrations in all B treatments, while needle B was not affected (Möttönen et al, 2001a). After repeated drought treatments, B concentrations decreased in needles; suggesting that translocation to needles was more impaired by stomatal closure than uptake to roots in Norway spruce seedlings (Möttönen et al, 2005). In a survey of Norway spruce stands in Finland, the foliar B concentrations were positively correlated with the occurrence of peatland mosses (Tamminen and Saarsalmi, 2004).…”

“…Similarly, B had little effect on the recovery of Norway spruce seedlings from a drought treatment as indicated by photosynthesis and water relations, but seedlings with high B grew somewhat better after drought. Only seedlings in the most severe drought treatment with low B (6 mg kg −1 in needles) had occurrences of tip dieback (Möttönen et al, 2005). In these cases, the actual damage was apparently caused by acute B deficiency in the growing point, as the drought would reduce water and boron translocation.…”

Fine roots of Picea abies compensate for drought stress in the rainfall reduction experiment

“…Induced drought stress leading to changes was more pronounced in Norway spruce seedlings grown under artificial conditions, whether it was a decrease of mycorrhizal colonization in seedlings as soon as exclusion of irrigation for 9 days (Möttönen et al, 2001), 6 days and subsequent 8 days (Möttönen et al, 2005) or 2-4 months in the third and the fifth year (Nilsen et al, 1998). The effect of drought on mycorrhizal colonization within Norway spruce stands (including our study) was not so apparent.…”