Yellow Autumn Research Articles

Do red and yellow autumn leaves make use of different photoprotective strategies during autumn senescence?

Our goal was to determine whether anthocyanin-producing species (red) use different photoprotective strategies to cope with excess light during fall senescence compared with non-anthocyanin-producing species (yellow). In a previous study, we found that a yellow species retained the photoprotective PsbS protein in late autumn, while a red species did not. Specifically, we tested the hypothesis that red species make less use of zeaxanthin and PsbS-mediated thermal dissipation, as they rely on anthocyanins for photoprotection. We monitored four red (Acer ginnala, Rhus typhnia, Parenthocissus quinquefolia, Viburnum dentatum) and four yellow species (Acer negundo, Ostrya virginiana, Vitis riparia, Zanthoxylum americanum) throughout autumn senescence and analyzed pigments, protein content, and chlorophyll fluorescence. We found yellow species retained the PsbS protein at higher levels, and had higher dark retention of zeaxanthin in late autumn relative to red species. All species retained lutein and the pool of xanthophyll cycle pigments in higher amounts than other carotenoids in late autumn. Our data support the hypothesis that red species use anthocyanins as a photoprotective strategy during autumn senescence, and therefore make less use of PsbS and zeaxanthin-mediated thermal dissipation. We also found species-specific variation in the particular combination of photoprotective strategies used.

The phenomenon of red and yellow autumn leaves: Hypotheses, agreements and disagreements.

Yellow and red autumn leaves are typical of many temperate/boreal woody plants. Since the 19th century, it has been either considered the non-functional outcome of chlorophyll degradation that unmasks the pre-existing yellow and red pigments or that the de novo synthesis of red anthocyanins in autumn leaves indicated that it should have a physiological function, although it was commonly ignored. Defending free amino acids and various other resources released especially following the breakdown of the photosynthetic system, and mobilizing them for storage in other organs before leaf fall, is the cornerstone of both the physiological and anti-herbivory hypotheses about the functions of yellow and red autumn leaf colouration. The complicated phenomenon of conspicuous autumn leaf colouration has received significant attention since the year 2000, especially because ecologists started paying attention to its anti-herbivory potential. The obvious imperfection of the hypotheses put forth in several papers stimulated many other scientists. Hot debates among physiologists, among ecologists, and between physiologists and ecologists have been common since the year 2000, first because the various functions of yellow and red autumn leaf colouration are non-exclusive, and second because many scientists were trained to focus on a single subject. Here, I will review the debates, especially between the photoprotective and the anti-herbivory hypotheses, and describe both the progress in their understanding and the required progress.

Trees growing in Eastern North America experience higher autumn solar irradiation than their European relatives, but is nitrogen limitation another factor explaining anthocyanin-red autumn leaves?: A comment on Peña-Novas and Marchetti 2021 (https://doi.org/10.1111/jeb.13903).

Trees growing at a particular latitude in Eastern North America (ENA) receive more autumn solar irradiation than do trees growing at the same latitude in Europe, a difference that could partly explain the higher percentage of anthocyanin-producing deciduous species in ENA compared with European floras. A proposed link between autumn light intensity and the production of anthocyanins is their function in photoprotection, which enables plants with red leaves to resorb nutrients for a longer time than can yellow or brown leaves. The innately 4-week-shorter foliage period of ENA trees compared with European ones may also play a role, as may stronger nitrogen limitation in poorer soils in ENA. We here test for a correlation between nitrogen access and fall anthocyanin in 126species (55genera, 22 families) from different temperate forests, using a Hierarchical Bayesian model and accounting for phylogenetic structure in the data. None of 81species with nitrogen-fixing symbionts produce autumn anthocyanin, whereas 42% of non-nitrogen-fixers do. Thus, when ample nitrogen is available from symbionts, the benefits of anthocyanin-derived photoprotection apparently do not outweigh the costs of anthocyanin production. If nitrogen limitation indeed plays a role in the dominance of red-autumn-colouring trees in ENA floras - while European floras predominantly produce yellow autumn leaves - there might also be continental differences in the frequency or abundance of nitrogen-fixing trees and shrubs, a new hypothesis that deserves testing.

A test of the photoprotection hypothesis for the evolution of autumn colours: Chlorophyll resorption, not anthocyanin production, is correlated with nitrogen translocation.

A prominent hypothesis for the adaptive value of anthocyanin production in the autumn leaves of trees and shrubs is that anthocyanins protect leaves from photooxidative stress at low temperatures, allowing a better resorption of nutrients-in particular, nitrogen-before leaf fall. While there is evidence that anthocyanins enable photoprotection, it is not clear whether this translates to improved nitrogen translocation and how this can explain inter-specific variation in autumn colours. A recent comparative analysis showed no correlation between temperature and anthocyanin production across species but did not analyse nitrogen content and nitrogen resorption efficiency. Here, we provide this comparison by analysing the nitrogen content of mature and senescent leaves and their autumn colours in 55 species of trees. We find no correlation between the presence of anthocyanins and the efficiency of nitrogen resorption. We find, instead, that nitrogen resorption is more efficient in species with yellow autumn colours, pointing to chlorophyll resorption, rather than anthocyanin synthesis, as the main determinant of nitrogen translocation efficiency. Hence, our results do not corroborate the photoprotection hypothesis for the evolution of autumn colours.

Quality, bioactive compounds and antioxidant capacity of raspberries cultivated in northern Mexico

ABSTRACT This study aimed to characterize the quality and bioactive compounds from five cultivars grown in Mexico´s northern region: Heritage, Summit, Harvest, and red and yellow Autumn. The physicochemical characteristics, DPPH anti-radical capacity, total phenolics, flavonoid and anthocyanins, polyphenolic profile, and ascorbic acid levels of the raspberries were assessed. The Harvest cultivar presented the highest weight and firmness and the lowest yield, total phenolics, and flavonoids. The yellow Autumn Bliss contained higher concentrations of polyphenols and ascorbic acid, and the red Autumn Bliss contained higher concentrations of flavonoids and anthocyanins and possessed a greater antioxidant capacity. The polyphenol profile indicated the presence of seven phenolic acids, namely, ellagic, gallic, caffeic, chlorogenic, p-coumaric, hydroxybenzoic, and protocatechuic acids; and four flavonoids, namely, catechin, quercetin-3-β-D-glucoside, quercetin-3-glucuronide, and rutin; these compounds were present in all the varieties, except for rutin, in yellow Autumn Bliss. The results of this study highlight the most valuable raspberry cultivars in terms of weight and firmness (Harvest), yield (Heritage), polyphenols and ascorbic acid (yellow Autumn Bliss), and anthocyanins and antioxidant capacity (red Autumn Bliss) in raspberries grown in northern Mexico.

A comparative analysis of the photoprotection hypothesis for the evolution of autumn colours

The adaptive value of autumn colours-the seasonal production of red anthocyanins observed in many species of trees and shrubs-is still debated. According to the photoprotection hypothesis, anthocyanins protect leaves from photo-inhibition and photo-oxidation at low temperatures, enabling the tree to reabsorb nutrients more efficiently before leaf fall. Hence, the hypothesis predicts that autumn colours are more likely to evolve in species growing in colder environments. We tested this prediction by comparing the climatic parameters of 237 North American tree species. We found that, although species with yellow autumn leaves grow under lower minimum temperatures than species with green leaves, there is no significant difference in temperature between species with red autumn leaves and species with green or yellow autumn leaves. We conclude that, although reabsorbing chlorophyll in autumn, and the consequent unmasking of yellow carotenoids, may be an adaptation to cold temperatures, the production of red anthocyanins is not. Hence, our interspecific comparative analysis does not support the photoprotection hypothesis as an explanation for the evolution of autumn colours.

The occurrence of red and yellow autumn leaves explained by regional differences in insolation and temperature.

Red or yellow autumn leaves have long fascinated biologists, but their geographical concentration in trees in Eastern North America (ENA) has defied evolutionary explanations. In this review, anthocyanins and xanthophylls are discussed in relation to their occurrence in different regions of the Northern Hemisphere, phylogenetic distribution and photoprotective function during the breakdown of chlorophylls. Pigments in senescing leaves that intercept incident light and dissipate the absorbed energy extend the time available for nutrient resorption. Experiments with Arabidopsis have revealed greatest anthocyanin photoprotective function at low temperatures and high light intensities, and high-resolution solar irradiation maps reveal that ENA and Asia receive higher irradiation than does Europe. In addition, ENA experiences higher temperature fluctuations in autumn, resulting in cold snaps during leaf senescence. Under common garden conditions, chlorophyll degradation occurs earlier in ENA species than in their European and East Asian relatives. In combination, strong solar irradiation, temperature fluctuations and, on average, 3-wk shorter vegetation periods of ENA species favour investment in pigments to extend the time for nutrient resorption before abscission, explaining the higher frequency of coloured species in ENA compared to Europe. We end by outlining research that could test this new explanation of bright New England autumns.

Virginia and Yellow Rail autumn migration ecology: synthesis using multiple data sets

AbstractVirginia and Yellow Rails are among the least studied birds in North America, and there is a specific lack of information about their autumn migration ecology and migratory habitat use. We conducted nocturnal surveys across 11 public wetlands in Missouri, USA from 2012-2016, and compared the timing of autumn migration from our surveys with three opportunistic datasets: 1) eBird records, 2) building strikes, and 3) state ornithological records. The observed timing (start and end date and duration) of Virginia Rail autumn migration varied between the opportunistic data and our surveys. Virginia Rail opportunistic data were bimodal, while our surveys had a single peak the second week in October. Yellow Rail autumn migration through Missouri peaked earlier in our surveys than opportunistic datasets which peaked during the second week in October. Both rails were found in moist soil habitats, however Virginia Rails selected perennial vegetation more than was available, while Yellow Rails selected annual plant species. Both species showed no selection for water depth and used shallow flooded wetlands. Understanding the autumn migration period and habitat requirements will allow wetland managers to better manage lands for autumn migrating Virginia and Yellow Rails.

Prerequisites for evolution: variation and selection in yellow autumn birch leaves

Prerequisites for evolution: variation and selection in yellow autumn birch leaves

Genotypic variation in yellow autumn leaf colours explains aphid load in silver birch

• It has been suggested that autumn-migrating insects drive the evolution of autumn leaf colours. However, evidence of genetic variation in autumn leaf colours in natural tree populations and the link between the genetic variation and herbivore abundances has been lacking. • Here, we measured the size of the whole aphid community and the development of green-yellow leaf colours in six replicate trees of 19 silver birch (Betula pendula) genotypes at the beginning, in the middle and at the end of autumn colouration. We also calculated the difference between green leaf and leaf litter nitrogen (N) and estimated the changes in phloem sap N loading. • Autumn leaf colouration had significant genetic variation. During the last survey, genotypes that expressed the strongest leaf reflectance 2-4 wk earlier had an abundance of egg-laying Euceraphis betulae females. Surprisingly, the aphid community size during the first surveys explained N loss by the litter of different birch genotypes. • Our results are the first evidence at the tree intrapopulation genotypic level that autumn-migrating pests have the potential to drive the evolution of autumn leaf colours. They also stress the importance of recognizing the role of late-season tree-insect interactions in the evolution of herbivory resistance.

Spring versus autumn leaf colours: Evidence for different selective agents and evolution in various species and floras

Red colouration is common in young and old leaves of broadleaf woody species. Assuming that leaf colours are adaptive, we examined, by comparing the colouration in young versus old leaves, the possibility that different selection agents may have operated on spring versus autumn leaf colouration. We observed spring versus autumn colouration in three very different woody floras (Finland, Japan and Israel) in order to allow for a broad ecological and evolutionary spectrum. The null hypothesis was that if the same selective agents operated in spring and autumn, it is expected that when spring leaves are red, they should always be red in autumn, and when spring leaves are green, they should be green or yellow in autumn. We found that green spring leaves are almost exclusively associated with yellow leaf colour at senescence in autumn. Species with red autumn leaves almost always have at least some red colouration in their spring leaves. However, about half of the species with red spring leaves have yellow autumn leaves. Brown autumn leaves were not common in the species we studied. As about half of the species with red spring leaves have yellow autumn leaves but not vice versa, we conclude that there are many cases in which the selecting agents for spring versus autumn leaf colour were not the same.

Why red‐dominated autumn leaves in America and yellow‐dominated autumn leaves in Northern Europe?

Why red‐dominated autumn leaves in America and yellow‐dominated autumn leaves in Northern Europe?

What Do Red and Yellow Autumn Leaves Signal

The widespread phenomenon of red and yellow autumn leaves has recently attracted considerable scientific attention. The fact that this phenomenon is so prominent in the cooler, temperate regions and less common in warmer climates is a good indication of a climate-specific effect. In addition to the putative multifarious physiological benefits, such as protection from photoinhibition and photo-oxidation, several plant/animal interaction functions for such coloration have been proposed. These include (1) that the bright leaf colors may signal frugivores about ripe fruits (fruit flags) to enhance seed dispersal; (2) that they signal aphids that the trees are well defended (a case of Zahavi’s handicap principle operating in plants); (3) that the coloration undermines herbivore insect camouflage; (4) that they function according to the “defense indication hypothesis,” which states that red leaves are chemically defended because anthocyanins correlate with various defensive compounds; or (5) that because sexual reproduction advances the onset of leaf senescence, the pigments might indicate to sucking herbivores that the leaves have low amounts of resources. Although the authors of hypotheses 3, 4, and 5 did not say that bright autumn leaves are aposematic, since such leaves are chemically defended, unpalatable, or both, we suggest that they are indeed aposematic. We propose that in addition to the above-mentioned hypotheses, autumn colors signal to herbivorous insects about another defensive plant property: the reliable, honest, and critical information that the leaves are about to be shed and may thus cause their mortality. We emphasize that all types of defensive and physiological functions of autumn leaves may operate simultaneously.

Sexual reproduction advances autumn leaf colours in mountain birch (Betula pubescens ssp. czerepanovii)

Autumnal change in leaf colour of deciduous trees is one of the most fascinating displays in nature. Current theories suggest that autumn leaf colours are adaptations to environmental stress. Here I report that the number of ripening female catkins altered timing of yellow autumn leaf colours in mountain birch. The tree's autumnal colour change was brought forward if the tree matured plenty of female catkins. Since yellow colour pigments in leaves are unmasked as leaf nitrogen is re-translocated, sexual reproduction may alter resource allocation at times of leaf senescence. Thus, our current view on the reasons for leaf senescence has to be re-examined, and a novel evolutionary explanation is needed for the appearance of yellow autumn leaf colours.

2- C-methyl- d-erythritol in leaves of Liriodendron tulipifera

A branched-chain alditol was isolated from yellow autumn leaves of the tulip tree, Liriodendron tulipifera and identified as 2- C-methyl- d-erythritol.

Chromoplasts in Rosa rugosa: Development and Chemical Characterization of Tubular Elements

Abstract 1. Development and fine structure of the chromoplasts in hips of Rosa rugosa have been in­ vestigated by electron and polarizing microscopy. 2. The chromoplasts develop from chloroplasts. During disorganization of the thylakoid system characteristic strutures become visible: ‘oblique’ grana, U-shaped thylakoids, and occassionally ‘thylakoid teeth’ as well as thylakoid anastomoses. - In this early stage, tubules appear in the plastid matrix. They are sometimes connected with membranes, especially with thylakoids. 3. In ripe hips the chromoplasts are packed with tubules. These chromoplast tubules, which attain lengths of up to at least 1.5 μm, are non-ramified and lie parallel to each other. Their diameter is variable, with a mean of 18 nm. They are polygonal in cross-section with electron-dense walls and electron-transparent cores. Association of ellipsoidal osmiophilic globules with the tubules can often be seen. Irregularly swollen remnants of former thylakoids are found in connection with these tubules. In spindle-shaped chromoplasts, the tubules are oriented parallel to the longitudinal axis. Positive birefringence and positive dichroism are observed. 4. The chemical composition of tubule fractions has been analyzed. The tubules contain appreciable amounts of carotenoids, phospho- and glycolipids, and proteins. 5. The origin and development of the tubules is discussed. It appears likely that reorganization of part of the thylakoid system and synthesis of carotenoids are involved in the formation of tubules. 6. The plastids in the yellow autumn leaves of Rosa rugosa contain globules but not tubules.

Information on the leaf lipids of Acer platanoides L. during autumn yellowing

The lipids of green and yellow leaves ofAcer platanoides L. have been investigated. Yellow leaves were found to contain phytyl linolenate, a further example of the formation of esters containing terpenoid alcohols and unsaturated fatty acids in yellow autumn leaves. The determination af squalene in leaves of the same tree showed an increase of squalene content during the whole season and the autumn colouration. Regarding the leaf lipids we conclude autumn colouration to be characterized by 3 facts: (1) Lipid degradation, (2) formation of esters and (3) accumulation of lipid intermediates.

A Spectrophotometric Study of Reflection of Light from Leaf Surfaces

1. The reflection of light from the surfaces of many kinds of leaves has been measured by means of a direct reading spectrophotometer, the measurements being made normal (that is, at an angle of 90⚬ to the leaf surface. The incident light, falling upon the leaf from the surface of a spherical housing, strikes the leaf at all angles. 2. The amount of reflection varies with the wave length, the maximum reflection falling usually at 540-560 mμ in green leaves. The value of the reflection in this region runs from 6-8 per cent in the darkest green leaves to 20-25 per cent in the lightest green specimens. 3. Hairiness or smoothness of cuticle does not necessarily mean high reflection. Leaves of Verbascum thapsus and Abutilon theophrasti show very little more reflection than leaves of non-hairy plants. The shiny cuticle of Morus rubra adds little to normal reflection. In some cases, however, as in the under surface reflection of Populus alba and Magnolia acuminata leaves, the hairs do increase the reflection. 4. The amount of reflection decreases with the age of the leaf. This is associated with the development of chlorophyll, which increases in amount very rapidly at first, and then more gradually for about two months, until the final depth of green color has been attained. The reflection then remains unchanged until the beginning of chlorophyll destruction at the close of summer. 5. White surfaces reflect almost equally across the spectrum, as seen in the under surface reflection of Populus alba; while albino leaves reflect mainly the longer radiations. There is absorption of the blue rays, corresponding to the yellowish color. The reflection from such surfaces is 40-50 per cent of the incident radiation. 6. The presence of mildew or other whitish superficial organisms increases the reflection of light very noticeably. In lilac the presence of Microsphaera alni increased the reflection more than 100 per cent. 7. Anthocyanin development is accompanied by a shift in the position of maximum reflection to the longer wave lengths. In Psedera the maximum reflection occurred at 640 mμ, while the normal maximum for green leaves is 540-560 mμ. 8. Yellow autumn coloration is much more brilliant than red. The reflection of yellow Betula leaves reached 42 per cent, with the maximum at 660 mμ. A leaf of Populus deltoides, less completely yellowed, reflected as much light, but the maximum reflection was in the yellow, at 580 mμ, instead of in the red. 9. In a considerable number of cases there is a depression of the reflection curve at 680 mμ. This obviously corresponds to the maximum absorption band of chlorophyll. The fact that it is evident is an argument for reflection from internal surfaces, in part. 10. The data presented are valuable in connection with the problem of income and outgo of energy in the leaf processes; but they must be supplemented with measurements in the invisible regions of the spectrum, particularly in the infra-red region, before a complete accounting of the energy utilization can be rendered.