Gymnosperms Demonstrate Patterns of Fine-root Trait Coordination Consistent with the Global Root Economics Space

Gymnosperms encompass a diverse group of mostly woody plants with high ecological and economic value, yet little is known about the scope and organization of fine-root trait diversity among gymnosperms due to the undersampling of most gymnosperm families and the dominance of angiosperm groups in recent syntheses. New and existing data were compiled for morphological traits (root diameter, length, tissue density, specific root length [SRL] and specific root area [SRA]), the architectural trait branching ratio, root nitrogen content [N] and mycorrhizal colonization. We used phylogenetic least squares regression and principal component analysis to determine trait-trait relationships and coordination across 66 species, representing 11 of the 12 extant gymnosperm families from boreal, temperate, subtropical and tropical biomes. Finally, we compared the relationship between family divergence time and mean trait values to determine whether evolutionary history structured variation in fine-root traits within the gymnosperm phylogeny. Wide variation in gymnosperm root traits could be largely captured by two primary axes of variation defined by SRL and diameter, and root tissue density and root nitrogen, respectively. However, individual root length and SRA each had significant correlations with traits defining both main axes of variation. Neither mycorrhizal colonization nor root branching ratio were closely related to other traits. We did not observe a directional evolution of mean trait values from older to more recently diverged gymnosperm families. Synthesis. Despite their unique evolutionary history, gymnosperms display a root economic space similar to that identified in angiosperms, likely reflecting common constraints on plants adapting to diverse environments in both groups. These findings provide greater confidence that patterns observed in broad syntheses justly capture patterns of trait diversity among multiple, distinct lineages. Additionally, independence between root architecture and other traits may support greater diversity in below-ground resource acquisition strategies. Unlike angiosperms, there were no clear trends towards increasingly thin roots over evolutionary time, possibly because of lower diversification rates or unique biogeographic history among gymnosperms, though additional observations are needed to more richly test evolutionary trends among gymnosperms

Effect of seed storage temperature on fine root development and mycorrhizal colonization of young Populus nigra seedlings

International audienceAbstractKey messageSeed storage temperature influences root anatomy of the endangered Populus nigra, and consequently may alter nutrient absorption. A lower temperature during seed storage (−20 and −196 °C) may preserve the potential for a suitable root system development after germination.ContextSeed storage conditions can be an important determinant of later seedling growth of Populus nigra L., an endangered tree species.AimsWe tested whether long-term seed storage temperature, −10, −20 or −196 °C, affects the pattern of seedling root traits responsible for resource acquisition as compared to seedlings of fresh seeds.MethodsWe analysed the morphology, anatomy, degree of mycorrhizal colonization, and biochemical composition of roots developed from seed stored for 24 months at five different temperatures (from 3 to −196 °C) commonly used to preserve genetic resources.ResultsExcept for root anatomy, we found no relationship between seed storage temperature and the root traits of seedlings. Among the various storage conditions, the proportion of roots with primary development in the first four orders was similar in seedlings developed from fresh seeds of from seeds stored at −196 or −20 °C. Nitrogen content in the roots was positively correlated with the proportion of (i) roots with primary development and (ii) the cortex width in the root diameter.ConclusionsHigher temperatures during seed storage reduced the proportion of roots with absorptive function (with primary development). Therefore, for preservation of P. nigra seeds we recommend lower temperatures such as −20 and −196 °C

Identification of genetics and hormonal factors involved in Quercus robur root growth regulation in different cultivation system

Abstract Understanding the molecular processes and hormonal signals that govern root growth is of paramount importance for effective forest management. While Arabidopsis studies have shed light on the role of the primary root in root system development, the structure of root systems in trees is considerably more intricate, posing challenges to comprehend taproot growth in acorn-sown and nursery-cultivated seedlings. In this study, we investigated Quercus robur seedlings using rhizotrons, containers, and transplanted containers to rhizotrons, aiming to unravel the impact of forest nursery practices on processes governing taproot growth and root system development. Root samples were subjected to RNA-seq analysis to identify gene expression patterns and perform differential gene expression and phytohormone analysis. Among studied cultivation systems, differentially expressed genes (DEGs) exhibited significant diversity, where the number of co-occurring DEGs among cultivation systems was significantly smaller than the number of unique DEGs in different cultivation systems. Moreover, the results imply that container cultivation triggers the activation of several genes associated with linolenic acid and peptide synthesis in root growth. Upon transplantation from containers to rhizotrons, rapid enhancement in gene expression occurs, followed by gradual reduction as root growth progresses, ultimately reaching a similar expression pattern as observed in the taproot of rhizotron-cultivated seedlings. Phytohormone analysis revealed that taproot growth patterns under different cultivation systems are regulated by the interplay between auxin and cytokinin concentrations. Moreover, the diversification of hormone levels within the root zone and cultivation systems allows for taproot growth inhibition and prompt recovery in transplanted seedlings. Our study highlights the crucial role of hormone interactions during the early stages of taproot elongation, influencing root system formation across

Preferential feeding and occupation of sunlit leaves favors defense response and development in the flea beetle, Altica brevicollis coryletorum--a pest of Corylus avellana.

The monophagous beetle, Altica brevicollis coryletorum, is a major leaf pest of Corylus avellana (common hazel). In contrast to majority of the other studied species of shrubs, sunlit leaves are grazed to a much greater extent than shaded leaves. Since the observation of a link between leaf irradiance level and A. brevicollis feeding is unique, we hypothesized that feeding preference of this beetle species is related to the speed needed to escape threats i.e. faster jumping. We also hypothesized that sunlit leaves are more nutritious and easier to consume than the leaves of shaded shrubs. Results indicated that beetle mass was greater in beetles occupying sunlit leaves, which is consistent with our second hypothesis. The study also confirmed under laboratory conditions, that larvae, pupae and beetles that were fed full-light (100% of full light) leaves were significantly heavier than those fed with shaded leaves (15% of full light). In the high irradiance conditions (higher temperature) duration of larval development is also reduced. Further results indicated that neither the concentration of soluble phenols, leaf toughness, or the number of trichomes could explain the insect's preference for sunlit leaves. Notably, measurements of jump length of beetles of this species, both in the field and under laboratory conditions, indicated that the defense pattern related to jumping was associated with light conditions. The jump length of beetles in the sun was significantly higher than in the shade. Additionally, in laboratory tests, beetle defense (jumping) was more strongly affected by temperature (15, 25, or 35°C for 24 h) than by leaf type. The effect of sunlit, higher nutrient leaves (greater level of non-structural carbohydrates) on defense (jumping) appears to be indirect, having a positive effect on insect mass in all developmental stages

Additional file 1 of Identification of genetics and hormonal factors involved in Quercus robur root growth regulation in different cultivation system

Additional file 1: Fig. S1. The effect of cultivation systems: rhizotron (black color), container (grey color) and transplanted (hacked) on IAA (A), IBA (B), IA-Ala (C), IA-Leu (D), IA-Phe (E), IA-Me (F) concentration in elongation zone of short, medium and long taproots of Q. robur seedlings. Fig. S2. The effect of cultivation systems: rhizotron (black color), container (grey color) and transplanted (hacked) on tZ (A), 2iP (B) concentration in elongation zone of short, medium and long taproots of Q. robur seedlings. Fig. S3. The effect of cultivation systems: rhizotron (black color), container (grey color) and transplanted (hacked) on ACC (A), ABA (B), SA (C) concentration in elongation zone of short, medium and long taproots of Q. robur seedlings. Fig. S4. The effect of cultivation systems: rhizotron (black color), container (grey color) and transplanted (hacked) on GA1 (A), GA3 (B), GA4 (C) GA7 (D) concentration in elongation zone of short, medium and long taproots of Q. robur seedlings. Fig. S5. The effect of cultivation systems: rhizotron (black color), container (grey color) and transplanted (hacked) on JA (A), MeJA (B) concentration in elongation zone of short, medium and long taproots of Q. robur seedlings. Fig. S6. The effect of cultivation systems: rhizotron (black color), container (grey color) and transplanted (hacked) on IAA (A), IBA (B), IA-Ala (C), IA-Leu (D), IA-Phe (E), IA-Me (F) concentration in meristematic zone of medium and long lateral roots of Q. robur seedlings. Fig. S7. The effect of cultivation systems: rhizotron (black color), container (grey color) and transplanted (hacked) on tZ (A), 2iP (B) concentration in meristematic zone of medium and long lateral root of Q. robur seedlings. Fig. S8. The effect of cultivation systems: rhizotron (black color), container (grey color) and transplanted (hacked) on ACC (A), ABA (B), SA (C) concentration in meristematic zone of medium and long lateral roots of Q. robur seedlings. Fig. S9. The effect of cultivation systems: rhizotron (black color), container (grey color) and transplanted (hacked) on GA1 (A), GA3 (B), GA4 (C) GA7 (D) concentration in meristematic zone of medium and long lateral roots of Q. robur seedlings. Fig. S10. The effect of cultivation systems: rhizotron (black color), container (grey color) and transplanted (hacked) on JA (A), MeJA (B) concentration in meristematic zone of medium and long lateral roots of Q. robur seedlings

Jump length (cm) of <i>Altica brevicollis coryletorum</i> flea beetles obtained from leaves of shrubs growing under natural, sunlit or shaded light conditions in the field.

<p>One-way ANOVA was used to determine the significance of differences in jump length for light conditions (<i>P</i><0.0001), sex (<i>P</i> = 0.9266) and light conditions × sex (<i>P</i> = 0.3161). Error bars denote standard error of the mean.</p

Occupation and feeding of the flea beetle, <i>Altica brevicollis coryletorum</i> on sunlit (A) and shaded (B) leaves of common hazel, <i>Corylus avellana</i>.

<p>Occupation and feeding of the flea beetle, <i>Altica brevicollis coryletorum</i> on sunlit (A) and shaded (B) leaves of common hazel, <i>Corylus avellana</i>.</p

Effect of light conditions (100% sunlight vs. 15% sunlight) on various leaf parameters in seedlings of <i>Corylus avellana</i> during the larval feeding period.

<p><b>Leaf toughness (A), water content (B), total non-structural carbohydrates (C), condensed tannins (D), nitrogen (E) and total soluble phenols (TPh) (F).</b> A one-way ANOVA was used to determine the significance of differences in leaf toughness (A) for light (<i>P</i><0.0001), date (<i>P</i><0.0001) and light × date (<i>P</i> = 0.2784); in water content (B) for light (<i>P</i><0.0001), date (<i>P</i><0.0001) and light × date (<i>P</i><0.0001); in total non-structural carbohydrates (C) for light (<i>P</i><0.0001), date (<i>P</i> = 0.0004) and light × date (<i>P</i><0.0001); in condensed tannins (D) for light (<i>P</i><0.0001), date (<i>P</i><0.0001) and light × date (<i>P</i><0.0001); in nitrogen (E) for light (<i>P</i><0.0001), date (<i>P</i><0.0001) and light × date (<i>P</i> = 0.0237); in total soluble phenols (F) for light (<i>P</i><0.0001), date (<i>P</i><0.0001) and light × date (<i>P</i><0.0030). Error bars denote standard error of the mean.</p

Density (number of trichomes\ mm² leaf blade) of all trichomes and glandular trichomes present on the leaf blade or along leaf veins, respectively, of leaves of <i>Corylus avellana</i> shrubs growing under field conditions (A, C) or seedlings growing und controlled, laboratory conditions (B, D).

<p>Error bars denote standard error of the mean.</p