The light screen hypothesis states that foliar anthocyanins shade the photosynthetic apparatus from excess light. In this paper we extend the light screen hypothesis, postulating that plant species at risk of photoinhibitory conditions during autumnal leaf senescence often utilize anthocyanins to protect the photosynthetic apparatus during the period of nutrient resorption. When senescence-related photosynthetic instabilities are compounded by other environmental stresses, particularly low temperature, severe photoinhibition may result in reduced resorption of critical foliar nutrients, which can significantly affect plant fitness. There is evidence that environments where low and often freezing temperatures are common in autumn selectively favor the production of anthocyanins in senescing foliage. The stimuli for, and the timing and location of, autumnal anthocyanin production are all consistent with a photoprotective role for these pigments in senescing leaves. Furthermore, differences in nitrogen allocation strategies between early and late successional species appear to affect photosynthetic stability during leaf senescence, resulting in a reduced need for foliar autumnal anthocyanins in many early successional plants. The ecological and physiological evidence presented in this paper suggest that, for many deciduous species, the production of anthocyanins provides effective photoprotection during the critical period of foliar nutrient resorption.

The resorption protection hypothesis, which states that anthocyanins protect foliar nutrient resorption during senescence by shielding photosynthetic tissues from excess light, was tested using wild-type (WT) and anthocyanin-deficient mutants of three deciduous woody species, Cornus sericea, Vaccinium elliottii (Chapmn.), and Viburnum sargentii (Koehne). WT Betula papyrifera (Marsh) was included to compare the senescence performance of a species that does not produce anthocyanins in autumn. Plants were subjected to three environmental regimes during senescence: an outdoor treatment; a 5-d high-stress (high light and low temperature) treatment followed by transfer to a low-stress environment and a low-stress treatment that served as control. In the outdoor treatment, the appearance of anthocyanins in senescing leaves of WT plants was concomitant with the development of photo-inhibition in mutant plants of all three anthocyanin-producing species. In the high-stress environment, WT plants maintained higher photochemical efficiencies than mutants and were able to recover when transferred to the low-stress environment, whereas mutant leaves dropped while still green and displayed signs of irreversible photooxidative damage. Nitrogen resorption efficiencies and proficiencies of all mutants in both stressful treatments were significantly lower than the WT counterparts. B. papyrifera displayed photochemical efficiencies and nitrogen resorption performance comparable with the highest of the anthocyanin-producing species in all three senescing environments, indicating a photoprotective strategy divergent from the other species studied. These results strongly support the resorption protection hypothesis of anthocyanins in senescing leaves.The role of anthocyanins in plant foliage has long been the subject of study and speculation (for review, see Chalker-Scott, 1999;Steyn et al., 2002). Foliar anthocyanins arise in a great diversity of plant species across a broad range of environments, often occurring in response to environmental stresses such as nutrient deficiency, drought, and low temperature (Steyn et al., 2002). In many species, anthocyanins are produced at specific physiological stages, appearing in expanding, mature, or senescing leaves exposed to high light. Observations over a century ago led to the light screen hypothesis, which states that foliar anthocyanins shade the photosynthetic apparatus from excess light (for review, see Wheldale, 1916).The resorption protection hypothesis (Hoch et al., 2001) proposed that the shading of photosynthetic tissues by anthocyanins produced during senescence helps protect the plant's ability to resorb foliar nutrients by shielding leaves from potentially harmful light levels. This hypothesis is based on the ideas that senescence-related processes lead to increased vulnerability to damage from visible light, resulting in reduced photosynthetic capacity (photo-inhibition) and that severe photo-inhibition during senescence can significantly affect a plant's ability to resorb foli...

Thirteen Betula species were tested for resistance to the birch leafminer, Femusa pusilla (Lepeletier), using no-choice assays. Birch leafminers were able to oviposit into expanding leaves of all Betula individuals tested. Larvae did not survive within any of the tested individuals of three species, B. alleghaniensis (Britt.), B. grossa (S. & Z.), and B. lenta (L.). Leafminer eggs deposited into the leaves of these species hatched, and larvae fed for a short period before dying. These three species were classified as highly resistant to birch leafminer, based on very low percent of mines (0.6-3.1%) with a diameter >3 mm. Eight species, B. papyrifera (Marsh), B. pendula (Roth), B. turkestanica (Litvin), B. glandulifira (Regal), B. ermanii (Cham.), B. platyphylla variety japonica [(Miq.) Hara], B. populifolia (Marsh) and B. maximowicziana (Regal) were classified as susceptible, with percent of mines >3 mm diameter of 87-94%. Two species, B. costata (Trautv.) and B. davurica (Pall.), displayed intermediate and variable resistance. B. davurica exhibited a mechanism of resistance not observed in the other species, Eggs oviposited into the leaves of resistant B. davurica individuals became surrounded by an area of discolored and necrotic tissue, and died. This response resembles the programmed cell death associated with a hypersensitive response.

Japanese spirea (Spiraea japonica L. f.), a popular landscape shrub, has shown the potential to become an invasive weed in both North America and Europe. Twenty commonly available S. japonica cultivars were evaluated for fertility using pollen and seed germination. Clones were grown in a randomized, replicated field plot, and additional seed samples were obtained from commercial nurseries and hand-pollinations in the greenhouse. Three sterile cultivars were identified: ‘Crispa’, ‘Dart's Red’, and ‘Neon Flash’. These cultivars demonstrated poor anther dehiscence and very low mean pollen germination, 2.7%, 3.0%, and 1.3%, respectively, which often produced abnormal pollen tubes. None of these three cultivars produced viable seed in the field plot, at commercial nurseries, or when hand-pollinated in the greenhouse, whereas seed germination from fertile clones ranged from 91.5% to 100%. The other 17 cultivars tested, which should be treated as entirely fertile for the purposes of invasive plant management, were ‘Albiflora’, ‘Anthony Waterer’, ‘Candlelight’, ‘Dakota Goldcharm’, var. alpina ‘Daphne’, ‘Flaming Mound’, ‘Flowering Choice’, ‘Froebelii’, ‘Golden Princess’, ‘Goldflame’, ‘Goldmound’, ‘Gumball’, ‘Lemon Princess’, ‘Little Princess’, ‘Magic Carpet’, ‘Norman’, and ‘Shibori’. Measurements of DNA content indicated that all tested clones are diploid; therefore, the observed sterility was not related to polyploidy. The identification of these three sterile cultivars can help reduce the use of fertile varieties in areas where Japanese spirea has shown the potential to become invasive.

ober Inhaltsstoffe des Rhizoma vom Geranium palustre L.B en z o y 1 k e t e n -0il t h y 1 -Np h e n y 1 -0, Nace t a1 (VII) Herstellung analog V aus I (2,l g) und Anlin (1,0 g). Das Rohkristallisat (2,5 g) wird auf dem Tonteller getrocknet, aus wenig Methanol rekristallisiert und mit Ather gewaschen. Hellgelbe Kristalle vom Schmp. 76,5-77,5'. Die methanolimhe Losung gibt rnit Eisen(II1)chlorid eine schwache, griinliche Fiirbung.C1,H,,NO2 (267,3) 0,5 g Oxalylketen-metal") mit der Mischung von 1 ml Dibenzylamin und 1 ml Dioxan bis zur Losung. Beim Erkalten erhillt man ein gelbes Kristallisat, das au8 reichlich khan01 rekristallisiert wird. Ausbeute: 0,9 g. Schmp. 170-171O. H 7, OO N 4,95Man erhitzt 0,5 g Oxalylketen-acetal in 2 ml Di-n-propylamin bis zur Losung, verdampft dann den AminuberschuB bei Raumtemperatur und kristallisiert den Ruckstand am Liurn. Man erhiilt 0,4 g gelbe Nadeln, die in den ublichen Losungsmitteh leicht loslich sind. lnfolge teilkeiser Zersetzung findet man einen unscharfen Schmp. zwischen 80-90°, je nach der Aufheizgeschwindigkeit. CUer Sumpfstorchschnabel, Geranium palustre L., ist eine niehrjahrige Staude mit handformig geteilten Blattern und purpurroten Bliiten. Er ist in Mitteleuropa an feuchten, schattigen Stellen nicht selten, wahrend er in Westdeutschland nur an einigen Stellen verbreitet ist. Die Rhizome fast aller Geraniumarten sind gerbstoffreich. AuSerdem enthalten die meisten Geraniumarten atherisches 01, Zucker, Pektine, Harze usw., wahrend Alkaloide und Glykoside nicht gefunden wurden. Da uber die Inhaltsstoffe des Rhizoms des Sumpfstorchschnabels noch nichts berichtet worden ist, wurde dieses besonders auf Gerbstoffe und evtl. andere Inhaltsstoffe untersucht. Als Untersuchungsmaterial diente eine frisch geerntete Droge rnit hellrotlichbraunem Bruch, die nach dem Trocknen zu einem groben Pulver vermahlen wnrde. Vorproben auf Gerbstoffe rnit Gelatinelosung, Eisenchloridlosung und Bleiazetatlosung fielen positiv aus. Ebenso verliefen die Reaktionen rnit Pormaldehyd-Salzsiiure und Bromwasser auf Catechine positiv, rnit Formaldehyd-Salzsanre und Bleimetatlosung auf Gallotannine hingegen negativ. Die vorliegende Droge enthielt Archiv 206. Band, Heft 2 7