New publication – A major trade-off between structural and photosynthetic investments operative across plant and needle ages in three Mediterranean pines

Text by Vivian Kuusk

Lots of species grow different looking leaves when they are young and adult. For example young conifers look more like little soft brushes rather than the forest giants, and lots of common houseplants look totally different in their natural habitat, because on our windowsills they produce only juvenile leaves (good example is devil`s ivy – Epipremnum aureum). The phenomena of juvenility has been a question for quite some time and we wanted to understand which morphological, anatomical and chemical changes occur in the needles upon juvenile-to-adult transition. As Mediterranean pines tend to keep juvenile needles longer than pines in temperate zone, stone pine (Pinus pinea), Aleppo pine (Pinus halepensis) and black pine (Pinus nigra) were chosen for the investigation. We found that juvenile needles are narrower, contain less dry mass per area and have thinner cell walls. Nitrogen content per dry mass was similar in all plant ages, but the photosynthetic tissue and size of chloroplasts was bigger in juvenile leaves. So we suggest that the ecological advantage of having juvenile leaves is of maximum carbon gain and establishing the saplings. The role of mature type leaves is to be more durable against various stress conditions, like for example mechanical stress from wind. I´d like to draw a parallel with human homes here – if you are young and don´t have lots of money, you live in a cheap condo, but when you have a bit more, you start thinking of building a house that would last a lifetime or more. Therefore plants invest more into growing durable leaves when they are older and have established their above- and underground parts well enough.

Citation: Kuusk, V., Niinemets, Ü., & Valladares, F. (2017). A major trade-off between structural and photosynthetic investments operative across plant and needle ages in three Mediterranean pines. Tree physiology, https://doi.org/10.1093/treephys/tpx139. (link to full text)

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Juvenile (left) and adult (right) foliage of Stone Pine (Pinus pinea) – (Pic from here)

Abstract:

Pine (Pinus) species exhibit extensive variation in needle shape and size between juvenile (primary) and adult (secondary) needles (heteroblasty), but few studies have quantified the changes in needle morphological, anatomical and chemical traits upon juvenile-to-adult transition. Mediterranean pines keep juvenile needles longer than most other pines, implying that juvenile needles play a particularly significant role in seedling and sapling establishment in this environment. We studied needle anatomical, morphological and chemical characteristics in juvenile and different-aged adult needles in Mediterranean pines Pinus halepensis Mill., Pinus pinea L. and Pinus nigra J. F. Arnold subsp. salzmannii (Dunal) Franco hypothesizing that needle anatomical modifications upon juvenile-to-adult transition lead to a trade-off between investments in support and photosynthetic tissues, and that analogous changes occur with needle aging albeit to a lower degree. Compared with adult needles, juvenile needles of all species were narrower with 1.6- to 2.4-fold lower leaf dry mass per unit area, and had ~1.4-fold thinner cell walls, but needle nitrogen content per dry mass was similar among plant ages. Juvenile needles also had ~1.5-fold greater mesophyll volume fraction, ~3-fold greater chloroplast volume fraction and ~1.7-fold greater chloroplast exposed to mesophyll exposed surface area ratio, suggesting overall greater photosynthetic activity. Changes in needle traits were similar in aging adult needles, but the magnitude was generally less than the changes upon juvenile to adult transition. In adult needles, the fraction in support tissues scaled positively with known ranking of species tolerance of drought (P. halepensis > P. pinea > P. nigra). Across all species, and needle and plant ages, a negative correlation between volume fractions of mesophyll and structural tissues was observed, manifesting a trade-off between biomass investments in different needle functions. These results demonstrate that within the broad trade-off, juvenile and adult needle morphophysiotypes are separated by varying investments in support and photosynthetic functions. We suggest that the ecological advantage of the juvenile morphophysiotype is maximization of carbon gain of establishing saplings, while adult needle physiognomy enhances environmental stress tolerance of established plants.

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Workgroup seminar – Jekaterina Aid about

Seminar of Chair of Crop Science and Plant Biology, Estonian Univ of Life Sciences .

Jekaterina Aid is a junior researcher and PhD-student in Estonian University of Life Sciences.

Title of the talk: Isoprene synthase functioning among family Fabaceae

Time: Wednesday, 24. January 2018 at 9.00

Place: Tartu, Kreutzwaldi 5 – D-143 (Metsamaja, Aquarium-room)

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Fab (aceous) volatile monsters (pic from here)

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New paper out – Diterpenoid fingerprints in pine foliage across an environmental and chemotypic matrix: Isoabienol content is a key trait differentiating chemotypes

Text by Lauri Laanisto

Intraspecific variability in functional traits has emerged in recent years as a quite important phenomenon. At least in plant ecology. Traditional view in life sciences has promoted between-species differences as much more significant drivers of ecological processes than within-species differences. Even though already Darwin pointed out that competition for resources is the fiercest within a population – individuals with the same niche fighting over the same stuff.

The current trends in trait-based ecology favor big data. It is logical to take as much data as possible and put all the numbers into one model and see if any general patterns emerge. Makes sense. But at least in the purely ecological studies, this approach to intraspecific trait variability has not really worked. In many cases, one being within-species variability, we should maybe use a deeper-going approach. And have smaller, but more insightful datasets than let´s say community weighted means. Angela Moles just published a very nice essay review about it.

In its own way, this study is very insightful in the context of intraspecific funcational variability. The way how VOC emissions of Pinus sylvestris depend on genetics, epigenetics and also phenotypically because of variable environmental conditions. And how these different sources of intraspecific variability might be related. So much questions in this regard are still unanswered…

Citation: Kännaste, A., Laanisto, L., Pazouki, L., Copolovici, L., Suhorutšenko, M., Azeem, M., Toom, L., Borg-Karlson, A.-K. & Niinemets, Ü. (2018). Diterpenoid fingerprints in pine foliage across an environmental and chemotypic matrix: Isoabienol content is a key trait differentiating chemotypes. Phytochemistry, 147, 80-88. (link to full text)

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Graphical abstract of the study (from here)

Abstract:

Highlights

• Isoabienol was the main diterpenoid alcohol in pine samples.
• Based on diterpenoid profiles we distinguished pine chemotypes.
• Needle contents of certain diterpenoids were related to foliar nitrogen contents.
• ‘Manoyl oxide – isoabienol pines’ were characteristic only to wetlands.

Abstract

Diterpenoids constitute an important part of oleoresin in conifer needles, but the environmental and genetic controls on diterpenoid composition are poorly known. We studied the presence of diterpenoids in four pine populations spanning an extensive range of nitrogen (N) availability. In most samples, isoabienol was the main diterpenoid. Additionally, low contents of (Z)-biformene, abietadiene isomers, manoyl oxide isomers, labda-7,13,14-triene and labda-7,14-dien-13-ol were quantified in pine needles. According to the occurrence and content of diterpenoids it was possible to distinguish ‘non diterpenoid pines’, ‘high isoabienol pines’, ‘manoyl oxide – isoabienol pines’ and ‘other diterpenoid pines’. ‘Non diterpenoid pines’, ‘high isoabienol pines’ and ‘other diterpenoid pines’ were characteristic to the dry forest, yet the majority of pines (>80%) of the bog Laeva represented ‘high isoabienol pines’. ‘Manoyl oxide – isoabienol pines’ were present only in the wet sites. Additionally, orthogonal partial least-squares analysis showed, that in the bogs foliar nitrogen content per dry mass (NM) correlated to diterpenoids. Significant correlations existed between abietadienes, isoabienol and foliar NM in ‘manoyl oxide – isoabienol pines’, and chemotypic variation was also associated by population genetic distance estimated by nuclear microsatellite markers. Previously, the presence of low and high Δ-3-carene pines has been demonstrated, but the results of the current study indicate that also diterpenoids form an independent axis of chemotypic differentiation. Further studies are needed to understand whether the enhanced abundance of diterpenoids in wetter sites reflects a phenotypic or genotypic response.

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New papers published – Glandular trichomes and stomatal conductance play crucial roles in protecting plants against ozone stress

Text by Shuai Li

Two papers studying how plants cope with ozone stress were recently published in the journal Plant Cell & Environment.

The first paper estimates the possible protective role of non-glandular and glandular trichomes on the leaf surface against ozone stress. This study analyzes ozone stress resistance of photosynthesis and induction of stress volatiles in 24 species with widely varying trichome characteristics and taxonomy, and demonstrated that the presence of glandular trichomes strongly reduced stomatal ozone uptake and ozone-dependent damage. The results indicate that leaf surface glandular trichomes constitute a major factor in reducing ozone toxicity and function as a chemical barrier which neutralizes the ozone before it enters the leaf. Once ozone enters plants mainly through the stomata, it leads to the onset of cell damage and elicitation of volatile emissions.

The second paper studies the key role of stomatal conductance in controlling ozone uptake, leaf injury and volatile release. This study investigates photosynthetic characteristics and VOC emissions in Phaseolus vulgaris leaves following acute ozone exposure under illumination and in darkness. The study also analyzes the key quantitative emission characteristics of volatile release and demonstrates different stress volatiles scale differently with ozone dose. This highlights stomatal closure due to darkness and pre-exposure to low-level ozone (priming) protected leaves against high-level ozone-induced injury.

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Trichomes are beautiful! (pic from here)

Citation 1Li, S., Tosens, T., Harley, P. C., Jiang, Y., Kanagendran, A., Grosberg, M., Jaamets, K. & Niinemets, Ü. (2018). Glandular trichomes as a barrier against atmospheric oxidative stress: relationships with ozone uptake, leaf damage and emission of LOX products across a diverse set of species. Plant, Cell & Environment, doi:10.1111/pce.13128 (link to full text)

Abstract:

There is a spectacular variability in trichome types and densities and trichome metabolites across species, but the functional implications of this variability in protection from atmospheric oxidative stresses remain poorly understood. The aim of the present study was to evaluate the possible protective role of glandular and non-glandular trichomes against ozone stress. We investigated the interspecific variation in types and density of trichomes and how these traits were associated with elevated impacts on visible leaf damage, net assimilation rate, stomatal conductance, chlorophyll fluorescence and emissions of lipoxygenase (LOX) pathway products in 24 species with widely varying trichome characteristics and taxonomy. Both peltate and capitate glandular trichomes played a critical role in reducing leaf ozone uptake, but no impact of non-glandular trichomes was observed. Across species, the visible ozone damage varied 10.1-fold, reduction in net assimilation 3.3-fold and release of LOX compounds 14.4-fold, and species with lower glandular trichome density were more sensitive to ozone stress and more vulnerable to ozone damage compared to species with high glandular trichome density. These results demonstrate that leaf surface glandular trichomes constitute a major factor in reducing ozone toxicity and function as a chemical barrier which neutralizes the ozone before it enters the leaf.

 

Citation 2: Li, S., Harley, P.C. & Niinemets, Ü. (2017) Ozone-induced foliar damage and release of stress volatiles is highly dependent on stomatal openness and priming by low-level ozone exposure in Phaseolus vulgaris. Plant Cell & Environment 40, 1984–2003. (link to full text)

Abstract:

Acute ozone exposure triggers major emissions of volatile organic compounds (VOC), but quantitatively, it is unclear how different ozone doses alter the start and the total amount of these emissions, and the induction rate of different stress volatiles. It is also unclear whether priming (i.e., pre-exposure to lower O3 concentrations) can modify the magnitude and kinetics of volatile emissions. We investigated photosynthetic characteristics and VOC emissions in Phaseolus vulgaris following acute ozone exposure (600 nmol mol-1 for 30 min) under illumination and in darkness and after priming with 200 nmol mol-1 O3 for 30 min. Methanol and lipoxygenase (LOX) pathway product emissions were induced rapidly, followed by moderate emissions of methyl salicylate (MeSA). Stomatal conductance prior to acute exposure was lower in darkness and after low O3 priming than in light and without priming. After low O3 priming, no MeSA and lower LOX emissions were detected under acute exposure. Overall, maximum emission rates and the total amount of emitted LOX products and methanol were quantitatively correlated with total stomatal ozone uptake. These results indicate that different stress volatiles scale differently with ozone dose and highlight the key role of stomatal conductance in controlling ozone uptake, leaf injury and volatile release.

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Blogyear Summary 2017

Text by Lauri Laanisto

The blog is now three years old. And it now has a one-year-old sisterblog as well – EcolChange blog. We have been keeping the approach, and trying to post mainly about our new publications. And this is the plan for the upcoming year(s) as well.

While blogging has been declared dead (numerous references available, just Google it), our venture is still growing. The number of visitors is still increasing – in 2015 we had 2300 unique visitors with 6900 blog views, last year these numbers were 3890/11300, and this year 5200/13300. Thus, on average exactly 100 visitors with 256 visits per week, and 14 visitors with 36 visits per day. The visits came from 97 different countries, and the total tally of countries from which we have had visits is now 116. The combined number of people following us is ~624, mostly through our Twitter account.

The growth is slightly surprising considering that the number of blog posts dropped quite a lot. From 80 and 77 posts in 2015 and 2016 to just 42 this year. Much of the drop is because a lot of energy went to the other blog. And it´s not because our publication rate has dropped. Nope. If anything, it´s vice versa. There´s a lot of papers from 2017 still waiting to be blogged about. Including, for example, a recent one in PNAS about global and local variabilities of plants traits.

Most popular posts in 2017:

1) Valentina´s post about how to measure injured leaf area (link)

2) Trevor Keenan´s post about potential bias in global trait lead estimates (link)

3) Linda-Liisa´s post about mesophyll conductance in living fossils (link)

4) Tiina´s post about some trade-offs underlying the leaf economics spectrum (link)

5) Lauri´s post about air pollution mitigating traits in urban trees (link)

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New member – welcome Hassan!

Text and pic by Hassan Yusuf Sulaiman
I have always been interested in studying the interaction among the components of the ecosystem/environment, specifically natural emission into the atmosphere. To gain a general understanding of the environment first; I enrolled into Bayero University Kano, in my home country of Nigeria, between 2006 and 2011, to study Physical Geography.
After earning a bachelor’s degree, I moved to Cyprus International University, Mersin 10, Turkey, in 2014, to bag a master’s degree in Environmental Sciences. During the course of my masters degree, I focused more on ecology and also emissions into the ambient air. Eventually, I wrote a thesis on natural Particulate matte emission into the atmosphere.
Over the years, I have been a teaching assistant at Yusuf Maitama Sule University, Kano; where I taught environment and plant related courses. My experiences as a teacher and as a student built up a curiosity in me to explore and find explanations to how plants influence the gaseous components of the atmosphere. Thus, I embarked on a journey to find the most enabling academic atmosphere to suit my interest. Yes, Niinemets Lab. is the right place for me considering the available facilities and the active working group led by a very strong authority with tens of thousands of citations to his name – Ülo Niinemets.
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I am set to make a huge contribution to science and humanity in general. My research will basically focus on “induced and constitutive benzenoid emission by plants”.

Yours,

Hassan Yusuf Sulaiman

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New paper published – Oak gall wasp infections of Quercus robur leaves lead to profound modifications in foliage photosynthetic and volatile emission characteristics

Text by Linda-Liisa Veromann-Jürgenson

Everyone with keen eyes that has been walking in wooded areas in the recent years must have noticed small growths on tree leaves called galls. Sometimes the infections can be massive, where it is hard to find one healthy leaf for a whole tree. This prompted the idea to study the physiological effects of galls on trees as such intense infections must have consequences. Furthermore, we were interested whether and how do plants protect themselves once they have been infected. We started the huge task of collecting data about the penalties of gall infections on tree physiology with oaks. An enormous diversity of gall wasp species can parasitize oak leaves, but the physiological implications of different gall wasp infections are poorly understood. We analysed the effects of infections by four different gall wasp species (Neuroterus anthracinus, N. albipes, Cynips divisa and C. quercusfolii) on foliage photosynthetic characteristics and volatile emission rates in Quercus robur that grow in Tartu Tammik planted by important people that have resided in or visited Tartu. Our work indicated that gall wasp infection resulted in major reductions in foliage photosynthesis rates and elicitation of emissions of green leaf volatiles, mono- and sesquiterpenes and benzenoids in infection severity-dependent manner. Different gall infections resulted in unique emission blends, highlighting a surprisingly selective host volatile response to various gall wasps.

Citation: Jiang, Y., Veromann‐Jürgenson, L. L., Ye, J., & Niinemets, Ü. (2017). Oak gall wasp infections of Quercus robur leaves lead to profound modifications in foliage photosynthetic and volatile emission characteristics. Plant, Cell & Environment, DOI: 10.1111/pce.13050 (link to full text)

oak galls

Oak galls (pic by Ülo Niinemets)

Abstract

Oak trees (Quercus) are hosts of diverse gall-inducing parasites, but the effects of gall formation on the physiology and biochemistry on host oak leaves is poorly understood. The influence of infection by four species from two widespread gall wasp genera, Neuroterus (N. anthracinus and N. albipes) and Cynips (C. divisa and C. quercusfolii), on foliage morphology, chemistry, photosynthetic characteristics, constitutive isoprene and induced volatile emissions in Q. robur was investigated. Leaf dry mass per unit area (MA), net assimilation rate per area (AA), stomatal conductance (gs), and constitutive isoprene emissions decreased with the severity of infection by all gall wasp species. The reduction in AA was mainly determined by reduced MA and to a lower extent by lower content of leaf N and P in gall-infected leaves. The emissions of lipoxygenase pathway (LOX) volatiles increased strongly with increasing infection severity for all four species with the strongest emissions in major vein associated species, N. anthracinus. Mono- and sesquiterpene emissions were strongly elicited in N. albipes and Cynips species, except in N. anthracinus. These results provide valuable information for diagnosing oak infections using ambient air volatile fingerprints and for predicting the impacts of infections on photosynthetic productivity and whole tree performance.

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