Problem fixing 

Nitrogen shortage is a significant challenge for plant growth, yet forest trees that can fix nitrogen tend to be less, rather than more, prevalent in nitrogen poor soils. It's a matter of tactics. Outside the tropics, obligate nitrogen fixers lose out to trees with a more flexible approach, missing the opportunity to participate in mature forest ecosystems.

See Efrat Sheffer et al. 1, 15182 (2015).

Tree ring circus

The wood of conifer trees is mainly composed of thick-walled cells called tracheids. After their production by the cambium, new tracheids enlarge (in a few days) and then build their thick and lignified secondary walls (stained red). This is the basis for the significant time lag between the increase in size and the increase in biomass in tree stems.

See Henri E. Cuny et al. 1, 15160 (2015).

The sharp end

Cacti are a culturally significant group, distributed primarily in arid environments, with a long history of human use for ornamental horticulture, food and medicine. And yet they are among the most threatened of plant groups with 31% of species at risk of extinction. The image shows Mammillaria herrerae, a critically endangered cactus endemic to Mexico.

See Bárbara Goettsch et al. 1, 15142 (2015).

Sink investment

A trehalose-6-phosphate phosphatase gene, OsTPP7, enhances anaerobic germination tolerance in rice, a key trait for direct-seeded rice, through modulation of sink strength. The gene is expressed in germinating embryos, coleoptiles and young roots — sink tissues that depend on reserve carbohydrates for proliferation.

See Tobias Kretzschmar et al. 1, 15124 (2015)

SNAREing voltage sensors

How plants coordinate ion transport with secretory traffic has been an open question for at least a century. Membrane voltage is ideally suited as a proxy for solute accumulation and cell turgor both driving and responding to all charged transport across the plant plasma membrane. The molecular machinery driving secretion binds the voltage sensors of potassium channels, co-opting them to couple traffic to membrane voltage.

See Christopher Grefen et al. 1, 15108 (2015)

Regressive tendencies

Most plant cells retain the ability to regenerate an entire plant but what stops them doing so? One answer is the POLYCOMB REPRESSIVE COMPLEX 2 (PRC2) which maintains suppression of specific genes through histone modification. In plants with dysfunctional PRC2 root hairs fall back into a disorganized state and even produce new embryos as shown here.

See Momoko Ikeuchi et al. 1, 15089 (2015)

Bacteria target photosynthesis 

Chlorophyll fluorescence captures changes in photosynthetic efficiency of Photosystem II in Arabidopsis leaves following infection with Pseudomonas.

See de Torres Zabala et al. 1, 15074 (2015)

Orchid architecture

Orchid flowers have a complex architecture and the molecular mechanisms underlying their development are no less arcane. Building on the classic ABC model of floral organ determination, competition between two protein complexes containing different AP3/AGL6 homologues determines the formation of the complex perianth patterns and their prominent lip.

See Hsu et al. 1, 15046 (2015)

Upturn in Growth

Movement of the inflorescence stem of Arabidopsis thaliana at 10-min intervals during gravitropism. The actin–myosin XI cytoskeleton regulates organ straightening to attain the new position more rapidly than would a series of diminishing overshoots in environmental stimuli.

See Okamoto et al. 1, 15031

Ringing the changes

Herbivorous insects influence forest structure and function.  Experiments at the Aspen Free-Air Carbon Dioxide Enrichment (FACE) facility in Wisconsin, USA suggest that elevated concentrations of carbon dioxide enhance insect-induced reductions in forest productivity, whereas elevated concentrations of ozone have the opposite effect. The cover shows an aerial view of the ring shaped experimental plots within the FACE faciliy.

See Couture et al. 1, 15016 

Two-pronged attack

Wheat ears from plants with a mutation in the PHOTOPERIOD DEPENDENT 1 (Ppd-1) gene. Many of the spikelets of these mutant plants are 'paired' producing two grains rather than the usual one. Ppd-1 acts by regulating the expression of FLOWERING LOCUS T. By modulating the expression of these two genes it may be possible to improve grain-producing spikelets and crop yield.

See Boden et al. 1, 14016

Up close and personal

The image shows detail of a flower from Petunia hybrida. To avoid self fertilization members of the Solanaceae family, such as petunia, use a system in which components of S-ribonucleases in pistils are detoxified by a collection of 16-20 different S-locus F-box proteins expressed in non-self pollen.

See Kubo et al. 1, 14005