#Nuclear throne stress series#

The aim of this review is to demonstrate the breadth of research influenced by phloem physiology and how research on this critical part of the vascular system can enhance our understanding of plant ecology and ecosystem function. For each of these topics, we provide discrete examples of how a phloem-focused line of inquiry could or already has enriched the field of physiological ecology. We focus on three broader topics: carbon–water interactions, carbon fluxes in plants and ecosystems, and biotic interactions. In this review, we describe research that provides a foundation for future work considering phloem physiology in an ecological and evolutionary context. These effects place the phloem in a central position for mediating plant–environment interactions and suggest that phloem structure could have important implications for a variety of processes from growth to reproduction (Fig. 2013) and phloem-mobile informational signals and secondary compounds (for reviews on molecular trafficking, see Turgeon & Wolf 2009 Lucas et al. The downstream effects of these changes can influence the movement of carbohydrates (Savage et al. 2013) such as drought (Sevanto 2014), may alter phloem transport.

This mechanism not only allows for transport to occur in multiple directions but also means that changes in the source and sink tissue, including those triggered by the biotic and abiotic environment (reviewed by Lemoine et al. This idea was first proposed by Ernst Münch ( 1930) and is the most widely accepted mechanism for phloem transport (for further discussion, see Knoblauch & Peters 2010). It is currently believed that phloem transport is driven by a pressure differential between the source and sink generated by local osmotic gradients in each tissue. Carbohydrates enter the phloem using one or a combination of passive and active loading mechanisms (see section on Phloem Loading, a Case Study: What Physiologists can Learn by Thinking About Ecology), which require different sugar concentration gradients in the mesophyll and vary in the amount of symplastic continuity that exists between the vascular and ground tissues. In the phloem, there are other cell types, including parenchyma and fibres, and of particular importance are the companion cells in angiosperms, which are often responsible for loading sugar into the phloem and for helping maintain metabolic function of neighbouring sieve tube elements (van Bel & Knoblauch 2000). Unlike transport cells in the xylem, sieve elements are under positive pressure and have intact cellular membranes (for recent reviews on phloem physiology, see De Schepper et al.

#Nuclear throne stress series#

Dashed arrows are fluxes that occur outside the plant but originate from resources transported in the phloem.Ĭarbon transport occurs in a series of stacked cells, sieve elements, which in angiosperms form long continuous conduits called sieve tubes (for details on cell ultrastructure, see Froelich et al. within the plant, aboveground and belowground). Water and carbon fluxes are noted in blue and orange, respectively, and separated based on where they occur (e.g. Transport of water and carbon into and out of the phloem. The phloem's role in shaping many ecological processes has intrigued scientists for decades, but proving a direct connection between phloem physiology and plant ecology remains challenging. Because carbon transport is influenced by source and sink activity, it can integrate changes that occur throughout the plant, potentially influencing everything from growth and allocation to defense and reproduction (Fig. This transport occurs in the phloem, a part of the vascular system that moves carbohydrates from photosynthetic and storage tissue (sources) to areas of active growth and metabolism (sinks). The majority of carbon used by vascular plants is not used where it is fixed but is transported to other metabolically active areas. 2012) and how carbon allocation affects many ecological processes ranging from community assembly to carbon cycling (Grime 2006 Migliavacca et al. Carbon fixed by plants serves as the basis of all life in terrestrial habitats, but there are still many questions that remain about how plants invest carbon during their lifetimes (Körner 2003 Sala et al.