Curtis Lubbe: How much do plants store and why?

In our February cover story, Curtis Lubbe from the Institute of Botany (Czech Academy of Sciences) presents his new workThe effect of moisture, nutrients, and disturbance on storage organ size and persistence in temperate herbs, highlights the importance of looking belowground to understand plants persistence and provides some extra artistic flavour to plant ecology.

About the paper

Curtis Lubbe – tired and in a Canadian prairie.
Curtis Lubbe – tired and in a Canadian prairie.

This paper is another vital step in our continuing quest to answer: how much do plants store and why?  We know that herbaceous perennial plants use specialized belowground organs (e.g. rhizome, tubers, bulbs, etc.) for both clonal growth and the storage of carbohydrates, but accurate and comprehensive measures of plant storage carbohydrates can be very labour intensive and expensive.  As a proxy for carbohydrate storage and allocation, we used detailed drawings to measure the volume of the belowground storage organs of hundreds of species of clonal plants.  We combined this measure with two core components of belowground plant life and allocation: growth, through the measure of annual lateral spread, and turnover, using annual increment persistence.  We then compared these measures to each other as well as a wide variety of environmental gradients.    

This paper is the culmination of many years of work in terms of preparing and compiling the drawings in the Clonal Plant Database by Jitka Klimešová and colleagues throughout the years, and the measuring by Alena Bartušková and Jianqiang Qian.  There was also the invaluable work of those who developed the environmental indicators (including my coauthors Jitka Klimešová and Tomáš Herben) and all of the rich theory we were able to access. 

An artistic interpretation of plant emotions. (c) Curtis Lubbe
An artistic interpretation of plant emotions. (c) Curtis Lubbe

            We affirmed the importance of belowground growth and turnover strategy by indicating the deviation of these two variables from each other as well as storage organ size, with plants capable of either growing belowground quickly or persisting a long time, but retaining the same volume of storage any given year.  Importantly, nutrient and light availability was largely irrelevant, indicating that variation in storage size is not just an artefact of productivity gradients. 

About the research

Rhizome persistence and lateral spread, in blue. (c) Curtis Lubbe
Rhizome persistence and lateral spread, in blue. (c) Curtis Lubbe

There is still so little known about plant storage strategy, so every granule of new information can hold a vital push in the right direction.  With this dataset we recognize the importance of moisture and disturbance frequency for allocation and growth, and for persistence, respectively.  We also see allocation belowground mirroring some of the theories based on the observation and study of aboveground processes.  These results are good inspiration for others to explore the relationships between growth, turnover, and storage in their own systems with these and even more environmental gradients.  Traits measured via images may also be viable for other systems.

Naive speculation of what plants may be doing belowground. (c) Curtis Lubbe
Naive speculation of what plants may be doing belowground. (c) Curtis Lubbe

Although this proxy for storage can provide useful hints about the ecology, it will be necessary to get more information on carbohydrate concentration and pool, in general and with focus on the sampling from the wide range of storage carbohydrate types.  There are many outstanding questions that remain unaddressed.  We still do not have sufficient information on the relationship of the size and turnover of belowground storage organs with storage carbohydrate contents.  The tissues within these organs further vary, as does their arrangement and coordination with the vasculature.  We also do not yet know how the chemical attributes of the different types of storage carbohydrates may coordinate with environmental gradients.  There are so many questions – we are still just getting started.   

About the author

I grew up in a desert in California, and when I moved to Pennsylvania for my studies, the wide variety and density of plants around was incredibly exciting – there were so many plants that there were even plants growing on other plants.  This was in strong contrast to the relatively regular spacing of the relatively few plant species I grew up around.  All this diversity and cohabitation really made me want to know why and how they were doing this.  The seasonal senescence, dormancy, and re-emergence of many herbaceous perennials in temperate systems is also endlessly fascinating.

A plant indoors, avoiding social commitments. (c) Curtis Lubbe

I am continuing my postdoc at the Institute of Botany for the Czech Academy of Sciences, in the working group of Jitka Klimešová, where we try to know as much about belowground organs and strategy as we can, and my focus has been on these questions of storage strategy and what these different storage traits mean for plant life.  Along with storage, I am expanding my exploration of how these different types of organs are used to move through the soil to gain their depth belowground and how this relates to plant life strategy.  I have continued to study these topics through surveys and experiments using the Central European flora, as well as species from abroad, either in situ or in nearby collections.  Along with my scientific work, plant belowground organs frequently find their way into my artwork, in both 2- and 3-dimensional forms. 

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