A discordance of seasonally covarying cues uncovers misregulated phenotypes in the heterophyllous pitcher plant Cephalotus follicularis

Organisms withstand normal ranges of environmental fluctuations by producing a set of phenotypes genetically programmed as a reaction norm; however, extreme conditions can expose a misregulation of phenotypes called a hidden reaction norm. Although an environment consists of multiple factors, how combinations of these factors influence a reaction norm is not well understood. To elucidate the combinatorial effects of environmental factors, we studied the leaf shape plasticity of the carnivorous pitcher plant Cephalotus follicularis . Clonally propagated plants were subjected to 12-week-long growth experiments in different conditions controlled by growth chambers. Here, we show that the dimorphic response of forming a photosynthetic flat leaf or an insect-trapping pitcher leaf is regulated by two covarying environmental cues: temperature and photoperiod. Even within the normal ranges of temperature and photoperiod, unusual combinations of the two induced the production of malformed leaves that were rarely observed under the environmentally typical combinations. We identified such cases in combinations of a summer temperature with a short-to-neutral day length, whose average frequency in the natural Cephalotus habitats corresponded to a once-in-a-lifetime event for this perennial species. Our results suggest that even if individual cues are within the range of natural fluctuations, a hidden reaction norm can be exposed under their discordant combinations. We anticipate that climate change may challenge organismal responses through not only extreme cues but also through uncommon combinations of benign cues.

Identification of an Isolate of Potato virus Y-Tuber Necrotic Strain on Clary Sage (Salvia sclarea)

In 1999, clary sage plants (Salvia sclarea L.) at the Herb Garden of Casola Valsenio (Emilia-Romagna Region, northern Italy) exhibited malformed leaves with yellow spots and line patterns. Sap from leaves of symptomatic sage plants caused symptoms in inoculated Chenopodium amaranticolor Coste et Reyn. plants (local chloro-necrotic lesions developed 7 to 10 days after inoculation) and Nicotiana tabacum L. ‘White Burley’ and ‘Samsun’ plants (systemic veinal necrosis developed ≈ 2 weeks after inoculation). Leaves from symptomatic sage plants tested positive for Potato virus Y (PVY) based on immunoelectron microscopy, gold-labeled decoration, and protein A sandwich enzyme-linked immunosorbent assay (ELISA), using antiserum to PVY (PVAS 50a, American Type Culture Collection, Manassas, VA). Double-antibody sandwich-ELISA, using specific monoclonal antibodies (BioReba AG, Reinach, Switzerland) to the tobacco veinal necrosis strain group of PVY (PVY-N), revealed that the PVY isolate from sage belonged to this group. Immunocapture-reverse transcription-polymerase chain reaction, using specific primers for PVY and the tuber necrotic strain of PVY (PVY-NTN), further classified the sage isolate as PVY-NTN (1). PVY-NTN causes serious damage to potato in Europe. Clary sage, one of the most important aromatic plants cultivated worldwide as a source of essential oils, represents a new natural host of PVY-NTN. Reference: (1) H. L. Weidemann and E. Maiss. J. Plant Dis. Prot. 103:337, 1996.

Boron deficiency in eucalypt plantations in China

Boron deficiency is identified as one of the more important causes of poor stem form and malformed leaves in plantations of Eucalyptusglobulus in Yunnan Province, and of Eucalyptusgrandis, Eucalyptustereticornis, and Eucalyptusurophylla in Guandong Province. Symptoms of B deficiency in E. globulus were rolled and malformed leaves, stem dieback, and a prostrate form. In E. urophylla, leaf margins became chlorotic then necrotic, leaves turned brittle and corky, shoots died back, and the upper stem nodes were enlarged supporting numerous short-lived axillary shoots. In E. grandis, stem dieback was preceded by the basipetal accumulation of anthocyanin in leaves. Boron-deficient E. tereticornis leaves developed marginal and interveinal chlorosis and recurved margins. Depressed foliar B concentrations were associated with visible symptoms. In E. globulus, the mean B concentration in young leaves of healthy trees was 31 mg/kg dry matter compared with 10 mg/kg in prostrate trees. Symptoms did not appear in E. globulus trees supplied with B fertilizer at planting. Normal shoot growth was restored in E. urophylla by the addition of B to the soil.