Leaf growth characteristics of Vitis vinifera and prediction of final lamina length for studies of powdery mildew

Total functional leaf area is a key factor in determining crop yield. A nonlinear mixed‐effects model was employed to estimate growth responses for individual leaves using repeated measures of lamina length ≥30 mm, in the absence of disease. Resulting growth curves make allowances for, and allow assessment of, leaf to leaf variability. The major source of variability in leaf growth was identified as differences in thermal time required to reach half final lamina length. Juvenile leaves of Vitis vinifera are susceptible to infection by the powdery mildew fungus (Erysiphe necator) which impairs leaf function. The model was used to predict unobserved final lamina length for a subset of leaves inoculated with E. necator immediately after observations ceased. The severity of infection by E. necator varies among infected leaves. A previous study identified which of the inoculated leaves developed symptoms of severe powdery mildew. Maximum severity of infection was found to occur when individual leaves were at 85.3–97.9% of predicted final lamina length.     

Cryopreservation of in vitro‐propagated protocorms of Caladenia for terrestrial orchid conservation in Western Australia

Cryopreservation is an important tool for the ex situ preservation of endangered plants. In this article, we describe the development of a cryopreservation protocol for orchid protocorms using the terrestrial Australian species Caladenia latifolia. Protocorms of C. latifolia generated asymbiotically each month on Murashige and Skoog (MS) medium containing 10 μM N6‐benzyladenine (BAP) provided explant sources for cryopreservation. Three size classes of protocorms were used as source explant material [small (S, ≤ 1 mm); medium (M, > 1 < 4 mm); large (L, ≥ 4 mm)] in combination with five desiccation treatments, i.e. 0, 0.4, 0.6, 0.8 and 1.0 M glycerol. After 2 days on desiccation medium, protocorms were treated with two cryoprotectant solutions (PVS2 and PVS4 at 0 °C for 15, 20, 25 and 30 min) before immersion in liquid nitrogen for 1 day. Protocorms were then removed from liquid nitrogen storage, warmed rapidly (in a 40 °C waterbath) and placed on three recovery media: half‐strength MS with 0.5 μM BAP, 0.5 μM 6‐furfurylaminopurine (kinetin) or 0.5 μM 1‐phenyl‐3‐(1,2,3‐thiadiazol‐5‐yl)‐urea (TDZ). Protocorms on recovery media were incubated at 25 °C under dark conditions and potential protocorm survival was observed at 60 and 90 days using a fluorescein diacetate (FDA) test for protocorm viability. Protocorm survival was correlated significantly with explant size. Large cryopreserved protocorms had the highest potential survival rate (> 90%) relative to small (< 10%) and medium (70–80%) protocorms. Different desiccation media treatments did not affect significantly the survival percentage (74–92%). Similarly, changing the cryoprotectant solution and time of incubation at 0 °C did not affect significantly potential protocorm survival (76–96%). Potential protocorm survival on various recovery media was not significantly different among treatments (88–100% survival). The study indicates that the cryopreservation of terrestrial orchid protocorms is technically feasible and provides a new and potentially highly beneficial tool in terrestrial orchid conservation where seed may be limited (because of species rarity), or as a means of storing and later utilizing the large surpluses of protocorms generated in propagation programmes. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, ?? , ??–??.     

High variation in foliage and leaf litter chemistry among 45 tree species of a neotropical rainforest community

Distinct ecosystem level carbon : nitrogen : phosphorus (C : N : P) stoichiometries in forest foliage have been suggested to reflect ecosystem-scale selection for physiological strategies in plant nutrient use. Here, this hypothesis was explored in a nutrient-poor lowland rainforest in French Guiana. Variation in C, N and P concentrations was evaluated in leaf litter and foliage from neighbour trees of 45 different species, and the litter concentrations of major C fractions were also measured. Litter C ranged from 45.3 to 52.4%, litter N varied threefold (0.68-2.01%), and litter P varied seven-fold (0.009-0.062%) among species. Compared with foliage, mean litter N and P concentrations decreased by 30% and 65%, respectively. Accordingly, the range in mass-based N : P shifted from 14 to 55 in foliage to 26 to 105 in litter. Resorption proficiencies indicated maximum P withdrawal in most species, but with a substantial increase in variation in litter P compared with foliage. These data suggest that constrained ecosystem-level C : N : P ratios do not preclude the evolution of highly diversified strategies of nutrient use and conservation among tropical rainforest tree species. The resulting large variation in litter quality will influence stoichiometric constraints within the decomposer food web, with potentially far-ranging consequences on nutrient dynamics and plant-soil feedbacks.     

A latitudinal cline and response to vernalization in leaf angle and morphology in Arabidopsis thaliana (Brassicaceae)

Adaptation to latitudinal patterns of environmental variation is predicted to result in clinal variation in leaf traits. Therefore, this study tested for geographic differentiation and plastic responses to vernalization in leaf angle and leaf morphology in Arabidopsis thaliana. Twenty-one European ecotypes were grown in a common growth chamber environment. Replicates of each ecotype were exposed to one of four treatments: 0, 10, 20 or 30 d of vernalization. Ecotypes from lower latitudes had more erect leaves, as predicted from functional arguments about selection to maximize photosynthesis. Lower-latitude ecotypes also had more elongated petioles as predicted by a biomechanical constraint hypothesis. In addition, extended vernalization resulted in shorter and more erect leaves. As predicted by functional and adaptive hypotheses, our results show genetically based clinal variation as well as environmentally induced variation in leaf traits.     

Clinical and pathologic manifestation of oesophagostomosis in African great apes: does self‐medication in wild apes influence disease progression?

Nodular worms (Oesophagostomum spp.) are common intestinal parasites found in cattle, pig, and primates including humans. In human, they are responsible for serious clinical disease called oesophagostomosis resulting from the formation of granulomas, caseous lesions or abscesses in intestinal walls. In wild great apes, the fecal prevalence of this parasite is high, but little information is available concerning the clinical signs and lesions associated. In the present study, we describe six cases of multinodular oesophagostomosis in free-ranging and ex-captive chimpanzees and captive gorillas caused by Oesophagostomum stephanostomum. While severe clinical signs associated with this infection were observed in great apes raised in sanctuaries, nodules found in wild chimpanzees do not seem to affect their health status. One hypothesis to explain this difference would be that in wild chimpanzees, access to natural environment and behavior such as rough leaves swallowing combined with ingestion of plants having pharmacological properties would prevent severe infection and decrease potential symptoms.     

Relationships between food quality and fitness in the desert locust, Schistocerca gregaria, and its distribution over habitats on the Red Sea coastal plain of Sudan

The effect of millet, Pennisetum typhoideum Rich. (Poaceae), leaf nitrogen content on fitness parameters of the desert locust, Schistocerca gregaria Forsk. (Orthoptera: Acrididae), was studied under laboratory conditions. Locusts reared on high‐nitrogen leaves were larger, developed faster, had higher survival, reproduced more and earlier, and showed greater synchronization than those fed on low‐nitrogen leaves. Active and passive cannibalism contributed to mortality when locusts were reared on low‐nitrogen leaves, but not when reared on high‐nitrogen leaves. Elevated leaf nitrogen content of host plants increased net reproduction and intrinsic rate of increase, and lowered generation time. The findings show that nitrogen content of host plants affects the potential for population increase in the desert locust. Leaf samples of common plant species were collected in the Heliotropium arbainense (Fresen.) (Boraginaceae) and Panicum turgidum (Forssk.) (Poaceae) plant communities on the Red Sea coastal plain of Sudan during the winters of 1999 and 2000. The levels of leaf nitrogen in host plants were comparable to those in the laboratory studies and consistently higher in plant samples from the Heliotropium community than in samples from the Panicum community. Both in 1999 and 2000, locust densities were much higher in the Heliotropium than in the Panicum plant community. It should be assessed whether the desert locust would be attracted to sites where host plants have high leaf nitrogen content, as this would not only increase their fitness, but also the likelihood of gregarization and outbreaks.     

Aquaporins and plant leaf movements

BaCKGROUND: Plant leaf movements can be mediated by specialized motor organs, the pulvini, or can be epinastic (i.e. based on different growth velocities of the adaxial and abaxial halves of the leaf). Both processes are associated with diurnally regulated increases in rates of membrane water transport, which in many cases has been shown to be facilitated by aquaporins. Rhythmic leaf movements are known from many plant species, but few papers deal with the involvement of aquaporins in such movements. SCOPE: Many details of the architecture and function of pulvini were worked out by Ruth Satter and co-workers using Samanea saman as a model organism. More recently a contribution of aquaporins to pulvinar movement in Samanea was demonstrated. Another model plant to study pulvinus-mediated leaf movements is Mimosa pudica. The contribution of both plasma membrane- and tonoplast-localized aquaporins to the seismonastic leaf movements in Mimosa was analysed. In tobacco, as an example of epinastic leaf movement, it was shown that a PIP1 aquaporin family member is an important component of the leaf movement mechanism.     

Heterologous expression, and biochemical and cellular characterization of CaPLA1 encoding a hot pepper phospholipase A1 homolog

Phospholipid signaling has been recently implicated in diverse cellular processes in higher plants. We identified a cDNA encoding the phospholipase A1 homolog (CaPLA1) from 5-day-old early roots of hot pepper. The deduced amino acid sequence showed that the lipase-specific catalytic triad is well conserved in CaPLA1. In vitro lipase assays and site-directed mutagenesis revealed that CaPLA1 possesses PLA1 activity, which catalyzes the hydrolysis of phospholipids at the sn -1 position. CaPLA1 was selectively expressed in young roots, at days 4–5 after germination, and rapidly declined thereafter, suggesting that the expression of CaPLA1 is subject to control by a development-specific mechanism in roots. Because transgenic work was extremely difficult in hot peppers, in this study we overexpressed CaPLA1 in Arabidopsis so as to provide cellular information on the function of this gene. CaPLA1 overexpressors had significantly longer roots, leaves and petioles, and grew more rapidly than the wild-type plants, leading to an early bolting phenotype with prolonged inflorescence. Microscopic analysis showed that the vegetative tissues of 35S:CaPLA1 plants contained an increased number of small-sized cells, which resulted in highly populated cell layers. In addition, mRNAs for cell cycle-controlled proteins and fatty acid catabolizing enzymes were coordinately upregulated in CaPLA1 -overexpressing plants. These results suggest that CaPLA1 is functionally relevant in heterologous Arabidopsis cells, and hence might participate in a subset of positive control mechanisms of cell and tissue growth in transgenic lines. We discuss possible biochemical and cellular functions of CaPLA1 in relation to the phospholipid signaling pathway in hot pepper and transgenic Arabidopsis plants.