Attenuation of incident light in Galax urceolata (Diapensiaceae): concerted influence of adaxial and abaxial anthocyanic layers on photoprotection

Although anthocyanin coloration in lower (abaxial) leaf cells has been documented for numerous species, the functional significance of this character has not been comprehensively investigated according to habitat or leaf orientation. Here, we demonstrate that abaxial anthocyanin may function as a photoprotectant, similarly to its purported role in upper (adaxial) cells, in leaves vulnerable to high irradiance incident on abaxial surfaces. Spectral scans were derived for Galax urceolata leaves with the following phenotypes: abaxial or adaxial anthocyanin only, abaxial and adaxial anthocyanin, and no anthocyanin. To determine whether anthocyanins conferred protection from photoinhibition, maximum photosystem II efficiencies of red (anthocyanic) and green (acyanic) surfaces were compared during and after exposure to photoinhibitory conditions. Leaves were either positioned with their adaxial surfaces facing the light source or inverted to expose abaxial surfaces. Spectral scans showed increased absorptance of 500-600 nm wavelengths by red surfaces (consistent with the absorbance spectrum of anthocyanin), regardless of whether that surface was abaxial or adaxial. Leaves with anthocyanin in either illuminated surface were also photoinhibited less than leaves lacking anthocyanin in that surface. These results suggest that anthocyanic layers reduce absorbed sunlight in the mesophyll not only for adaxial surfaces, but also for the abaxial. Adaxial/abaxial anthocyanin plasticity may therefore be adaptive in high-light environments or during light-sensitive developmental stages where leaf orientation and/or substrate albedo are variable.     

A comparison of mechanisms of desiccation tolerance among three angiosperm resurrection plant species

The mechanisms of protection against mechanical and oxidative stress were identified and compared in the angiosperm resurrection plants Craterostigma wilmsii, Myrothamnus flabellifolius and Xerophyta humilis. Drying-induced ultrastructural changes within mesophyll cells were followed to gain an understanding of the mechanisms of mechanical stabilisation. In all three species, water filled vacuoles present in hydrated cells were replaced by several smaller vacuoles filled with non-aqueous substances. In X. humilis, these occupied a large proportion of the cytoplasm, preventing plasmalemma withdrawal and cell wall collapse. In C. wilmsii, vacuoles were small but extensive cell wall folding occurred to prevent plasmalemma withdrawal. In M. flabellifolius, some degree of vacuolation and wall folding occurred, but neither were sufficient to prevent plasmalemma withdrawal. This membrane was not ruptured, possibly due to membrane repair at plasmodesmata junctions where tearing might have occurred. In addition, the extra-cytoplasmic compartment appeared to contain material (possibly similar to that in vacuoles) which could facilitate stabilisation of dry cells.Photosynthesis and respiration are particularly susceptible to oxidative stress during drying. Photosynthesis ceased at high water contents and it is proposed that a controlled shut down of this metabolism occurred in order to minimise the potential for photo-oxidation. The mechanisms whereby this was achieved varied among the species. In X. humilis, chlorophyll was degraded and thylakoid membranes dismantled during drying. In both C. wilmsii and M. flabellifolius, chlorophyll was retained, but photosynthesis was stopped due to chlorophyll shading from leaf folding and anthocyanin accumulation. Furthermore, in M. flabellifolius thylakoid membranes became unstacked during drying. All species continued respiration during drying to 10% relative water content, which is proposed to be necessary for energy to establish protection mechanisms. Activity of antioxidant enzymes increased during drying and remained high at low water contents in all species, ameliorating free radical damage from both photosynthesis and respiration. The nature and extent of antioxidant upregulation varied among the species. In C. wilmsii, only ascorbate peroxidise activity increased, but in M. flabellifolius and X. humilis ascorbate peroxidise, glutathione reductase and superoxide dismutase activity increased, to various extents, during drying. Anthocyanins accumulated in all species but this was more extensive in the homoiochlorophyllous types, possibly for protection against photo-oxidation.     

Photosynthetic costs and benefits of abaxial versus adaxial anthocyanins in Colocasia esculenta ‘Mojito’

Main conclusion

Anthocyanins in upper (adaxial) leaf tissues provide greater photoprotection than in lower (abaxial) tissues, but also predispose tissues to increased shade acclimation and, consequently, reduced photosynthetic capacity. Abaxial anthocyanins may be a compromise between these costs/benefits. Plants adapted to shaded understory environments often exhibit red/purple anthocyanin pigmentation in lower (abaxial) leaf surfaces, but rarely in upper (adaxial) surfaces. The functional significance of this color pattern in leaves is poorly understood. Here, we test the hypothesis that abaxial anthocyanins protect leaves of understory plants from photo-oxidative stress via light attenuation during periodic exposure to high incident sunlight in the forest understory, without interfering with sunlight capture and photosynthesis during shade conditions. We utilize a cultivar of Colocasia esculenta exhibiting adaxial and abaxial anthocyanin variegation within individual leaves to compare tissues with the following color patterns: green adaxial, green abaxial (GG), green adaxial, red abaxial (GR), red adaxial, green abaxial (RG), and red adaxial, red abaxial (RR). Consistent with a photoprotective function of anthocyanins, tissues exhibited symptoms of increasing photoinhibition in the order (from least to greatest): RR, RG, GR, GG. Anthocyanic tissues also showed symptoms of shade acclimation (higher total chl, lower chl a/b) in the same relative order. Inconsistent with our hypothesis, we did not observe any differences in photosynthetic CO₂ uptake under shade conditions between the tissue types. However, GG and GR had significantly (39 %) higher photosynthesis at saturating irradiance (A _sat) than RG and RR. Because tissue types did not differ in nitrogen content, these patterns likely reflect differences in resource allocation at the tissue level, with greater nitrogen allocated toward energy processing in GG and GR, and energy capture in RG and RR (consistent with relative sun/shade acclimation). We conclude that abaxial anthocyanins are likely advantageous in understory environments because they provide some photoprotection during high-light exposure, but without the cost of decreased A _sat associated with adaxial anthocyanin-induced shade syndrome.     

Protein dynamics in thylakoids of the desiccation-tolerant plant Boea hygroscopica during dehydration and rehydration

Plants of Boea hygroscopica F. Muell were dehydrated to 9% relative water content (RWC) by withholding water for 26 d, and afterward the plants were rehydrated. Leaves were taken from control plants after 7, 12, and 26 d from the beginning of dehydration, and after 6 and 48 h from rehydration. The RWC decreased by 80% during dehydration, but the leaves regained RWC with rehydration. Dehydrated plants showed lesser amounts of proteins, lipids, and chlorophyll, all of which increased following rewatering. The lipid-to-protein ratio, which decreased during dehydration, returned to control level after 48 h of rehydration. Thylakoid lipids were more unsaturated when RWC reached the value of 9%. EPR measurements of spin-labeled proteins showed the presence of three different groups of proteins with different mobility in thylakoid membranes. The rotational correlation time of groups 1 and 2 increased with dehydration and decreased upon rehydration, whereas group 3 showed little changes. Desiccation did not cause thylakoid swelling or breakage, but the membrane system assemblage showed changes in thylakoid stacking. After 48 h of rehydration the membrane system recovered completely the organization of the fully hydrated state, showing several well-defined and regularly distributed grana.     

Light as a hazard for the desiccation-resistant 'resurrection' fern Polypodium polypodioides

Abstract. Using fluorescence measurements at 77 K, the susceptibility to photoinhibition was determined for variously dehydrated leaves of the desiccation–resistant fern Polypodium polypodioides. As expected, water loss increased the potential danger of light-induced damage. However, the long-term consequences of that damage differed depending on the hydration state of the leaves during the light treatment, suggesting that different targets were affected. This became evident when the rehydrated leaves were subjected to conditions conducive to recovery from typical photoinhibition. After an exposure to high photon flux densities, full restoration of normal photochemical efficiencies occurred only when the photoinhibitory treatment had occurred while the leaves were fully hydrated, or when the dehydration had reached a stage at which only the primary charge separation and storage were operative. On the other hand, lesions caused by high light intensities in slightly dehydrated leaves which had retained some electron transport activity between the two photosystems, or in desiccated leaves incapable of any measureable photosynthetic functions, were very inefficiently or not at all repaired. One unexpected hazard of high light intensities for dehydrated leaves turned out to be further desiccation which could reach a threshold at which extensive cellular damage began to ensue. In nature, P. polypodioides avoids light–induced damage by rolling its leaves during dehydration so that only the reflectant abaxial leaf surface is exposed to ambient light, and by occupying shaded habitats.     

Three-stage Transformation of Chlorophyll Transient Fluorescence Pattern Under Sustained Dehydration and the Discovery of Critical Water Content in Seaweeds (in English)

The chlorophyll fluorescence kinetics of marine red alga Grateloupia turuturu Yamada, green alga Ulva pertusa Kjellm and brown alga Laminaria japonica Aresch during natural sustained dehydration were monitored and investigated. The pulse amplified modulation (PAM) system was used to analyze the distinct fluorescence parameters during thallus dehydration. Results proved that the fluorescence kinetics of different seaweed all showed three patterns of transformation with sustained water loss. These were: 1) peak kinetic pattern (at the early stage of dehydration fluorescence enhanced and quenched subsequently, representing a normal physiological state). 2) plateau kinetic pattern (with sustained water loss fluorescence enhanced continuously but quenching became slower, finally reaching its maximum). 3) Platform kinetic pattern (fluorescence fell and the shape of kinetic curve was similar to plateau kinetic pattern). A critical water content (CWC) could be found and defined as the percentage of water content just prior to the fluorescence drop and to be a significant physiological index for evaluation of plant drought tolerance. Once thallus water content became lower than this value the normal peak pattern can not be recovered even through rehydration, indicating an irreversible damage to the thylakoid membrane. The CWC value corresponding to different marine species were varied and negatively correlated with their desiccation tolerance, for example. Laminaria japonica had the highest CWC value (around 90%) and the lowest dehydration tolerance of the three. In addition, a fluorescence “burst” was found only in red algae during rehydration. The different fluorescence parameters Fo , Fv and Fv/ Fm were measured and compared during water loss. Both Fo and Fv increased in the first stage of dehydration but Fv / Fm kept almost constant. So the immediate response of in vivo chlorophyll fluorescence to dehydration was an enhancement. Later with sustained dehydration Fo increased continuously while Fv decreased and tended to become smaller and smaller. The major changes in fluorescence (including fluorescence drop during dehydration and the burst during rehydration) were all attributed to the change in Fo instead of Fv . This significance of Fo indicates that it is necessary to do more research on Fo as well as on its relationship with the state of thylakoid membrane.     

持续脱水下海藻叶绿素瞬变荧光模式的三阶段转换及临界水量的发现

在自然干燥条件下,跟踪研究了海洋红藻带形蜈蚣藻（Grateloupia turuturu Yamada),绿藻石莼（Ulva pertusa Kjellm)和褐藻海带（Laminaria japonica Aresch)的叶绿素荧光动力学曲线的变化,并用脉冲调制荧光仪分析了藻体脱水过程中的各个荧光参数。结果表明,在持续脱水过程中,3类海藻的荧光动力学曲线都显示出3个阶段的变化,即：1）在脱水开始时正常的峰形曲线;2）荧光上升至最高时持平、形成了高原型曲线;3）荧光跌落变成平台型曲线,发现荧光跌落前藻体的含水百分数是一个重要的生理指标,称为临界水量（CWC）。一旦藻体失水至低于此临界水量时,即便复水也不能使原来的峰形曲线得以恢复,说明脱水可能引起了叶绿体类囊体膜的不可逆损伤。临界水量可以用来衡量不同海藻的耐旱力,其数值高低随不同海藻而不同,并与其耐旱力成负相关。如在上述3大类海藻中,海带的CWC值最高（约90％）,但其耐旱性最差。此外,在红藻（只有红藻）经受干燥后作复水处理时,观察到有荧光急剧上升（爆发）的现象。对海膜脱水前后的几个荧光参数（F0、Fv、Fv/Fm)作了测定和比较,发现F0和Fv在脱水的第一阶段都上升,而v/Fm值维持基本不变。因此可以得出结论,活体叶绿素荧光对干旱的最初响应是立即增强,当继续失水时,F0保持上升而Fv却下降并越来越低,故此时总荧光的变化（包括荧光的跌落和爆发）主要是由F0的变化所引起的,因而进一步研究F0与脱水时类囊体膜状态变化的关系具有重要意义。     

Effects of Dehydration and Rehydration on Photosynthesis of Detached Leaves of the Resurrective Plant Boea hygrometrica

Fluorescence induction kinetics was used to investigate the effects of dehydration and rehydration on photosynthesis of detached leaves of the desiccation-tolerant, resurrective plant Boea hygrometrica (Bunge) R. Br. In comparison with the desiccation-intolerant plant Chirita heterotricha Merr., the PSⅡphotochemical activity of Boea hygrometrica was characterized by a faster decline during dehydration and a much higher capacity of recovery during rehydration. By means of native PAGE, it was further shown that the thylakoid pigment-protein complexes of Boea hygrometrica were highly stable during dehydration and rehydration. These features may contribute to the extreme desiccation resistance of photosynthesis apparatus of resurrective plant Boea hygrometrica.     

The anti-photooxidation of anthocyanins-rich leaves of a purple rice cultivar

In the leaf of rice (Oryza sativa L.) cultivar Yunnan purple rice,the anthocyanins with an obvious absorption peak at 530nm were distributed in the cells of upper and lower epidermis,bulliform tissue and bristle. The maximal photosynthetic oxygen evolution rate and chlorophyll content in flag leaves were 28% and 23%,respectively,more than the common green leaf rice cultivar Chijiaoru-anzhan. Higher chlorophyll content is probably one of the physiological adaptations for enhancing light harvesting capacity of the antenna in photosystems in this cyanic leaves species. Upon the photooxidation of leaf segments mediated by methyl viologen in weak light for 3 days,the distinct bleaching of anthocyanins in purple rice was associated with the reduction of scavenging ability to DPPH· free radical ability and the increase in membrane leakage rate. But almost no changes in contents of flavonoids and total phenolics were observed. Chlorophyll fluorescence parameters Fv/Fo,qP and φPSⅡ decreased with the increase in NPQ and DES of xanthophylls cycle after photooxidation treatment. Green rice leaves showed more decrease in DPPH· scavenging rate and more increase in cell membrane leakage rate but showed a trace of anthocyanins during photooxidation. It is sug-gested that anthocyanin may be a beneficial and primary antioxidant in sun cyanic rice leaves against oxidative stress induced by environmental adversity. And photooxidation could induce different changing patterns of anthocyanins between the tested purple and green rice leaves.     

The anti-photooxidation of anthocyanins-rich leaves of a purple rice cultivar

In the leaf of rice (Oryza sativa L.) cultivar Yunnan purple rice, the anthocyanins with an obvious absorption peak at 530nm were distributed in the cells of upper and lower epidermis, bulliform tissue and bristle. The maximal photosynthetic oxygen evolution rate and chlorophyll content in flag leaves were 28% and 23%, respectively, more than the common green leaf rice cultivar Chijiaoruanzhan. Higher chlorophyll content is probably one of the physiological adaptations for enhancing light harvesting capacity of the antenna in photosystems in this cyanic leaves species. Upon the photooxidation of leaf segments mediated by methyl viologen in weak light for 3 days, the distinct bleaching of anthocyanins in purple rice was associated with the reduction of scavenging ability to DPPH · free radical ability and the increase in membrane leakage rate. But almost no changes in contents of flavonoids and total phenolics were observed. Chlorophyll fluorescence parameters Fv/Fo, qP and ϕ_PSII decreased with the increase in NPQ and DES of xanthophylls cycle after photooxidation treatment. Green rice leaves showed more decrease in DPPH · scavenging rate and more increase in cell membrane leakage rate but showed a trace of anthocyanins during photooxidation. It is suggested that anthocyanin may be a beneficial and primary antioxidant in sun cyanic rice leaves against oxidative stress induced by environmental adversity. And photooxidation could induce different changing patterns of anthocyanins between the tested purple and green rice leaves.     

Strength of winter leaf redness as an indicator of stress vulnerable individuals in Pistacia lentiscus

Leaf anthocyanins are believed to afford protection against photoinhibition, yet the dependence of protection on actual anthocyanin concentrations has not been investigated. To that aim, non-invasive optical methods (spectral reflectance and chlorophyll fluorescence) were used to assess the levels of anthocyanins and chlorophylls as well as photosystem II photochemical efficiency in hundreds of leaves from the mastic tree (Pistacia lentiscus), which displays in the field a continuum of leaf tints during winter from fully green to fully red. Contrary to expectations based on the photoprotective hypothesis, the strength of leaf redness was positively correlated to the extent of mid-winter chronic photoinhibition and negatively correlated to leaf chlorophyll contents. Hence, a photoprotective role for anthocyanins is not substantiated. Instead, we argue that winter leaf redness may be used reliably, quickly and non-invasively to locate vulnerable individuals in the field.     

Protection of thylakoids against combined light and drought by a lumenal substance in the resurrection plant Haberlea rhodopensis

Background and Aims

Haberlea rhodopensis is a perennial, herbaceous, saxicolous, poikilohydric flowering plant that is able to survive desiccation to air-dried state under irradiance below 30 µmol m⁻² s⁻¹. However, desiccation at irradiance of 350 µmol m⁻² s⁻¹ induced irreversible changes in the photosynthetic apparatus, and mature leaves did not recover after rehydration. The aim here was to establish the causes and mechanisms of irreversible damage of the photosynthetic apparatus due to dehydration at high irradiance, and to elucidate the mechanisms determining recovery.

Methods

Changes in chloroplast structure, CO₂ assimilation, chlorophyll fluorescence parameters, fluorescence imaging and the polypeptide patterns during desiccation of Haberlea under medium (100 µmol m⁻² s⁻¹; ML) irradiance were compared with those under low (30 µmol m⁻² s⁻¹; LL) irradiance.

Key Results

Well-watered plants (control) at 100 µmol m⁻² s⁻¹ were not damaged. Plants desiccated at LL or ML had similar rates of water loss. Dehydration at ML decreased the quantum efficiency of photosystem II photochemistry, and particularly the CO₂ assimilation rate, more rapidly than at LL. Dehydration induced accumulation of stress proteins in leaves under both LL and ML. Photosynthetic activity and polypeptide composition were completely restored in LL plants after 1 week of rehydration, but changes persisted under ML conditions. Electron microscopy of structural changes in the chloroplast showed that the thylakoid lumen is filled with an electron-dense substance (dense luminal substance, DLS), while the thylakoid membranes are lightly stained. Upon dehydration and rehydration the DLS thinned and disappeared, the time course largely depending on the illumination: whereas DLS persisted during desiccation and started to disappear during late recovery under LL, it disappeared from the onset of dehydration and later was completely lost under ML.

Conclusions

Accumulation of DLS (possibly phenolics) in the thylakoid lumen is demonstrated and is proposed as a mechanism protecting the thylakoid membranes of H. rhodopensis during desiccation and recovery under LL. Disappearance of DLS during desiccation in ML could leave the thylakoid membranes without protection, allowing oxidative damage during dehydration and the initial rehydration, thus preventing recovery of photosynthesis.Key words: Haberlea rhodopensis, resurrection plant, electron microscopy, blue–green fluorescence, chlorophyll fluorescence     

Protective effect of supplemental anthocyanins on Arabidopsis leaves under high light

Ten anthocyanin components have been detected in roots of purple sweet potato (Ipomoea batatas Lam.) by high‐performance liquid chromatography coupled to diode array detection and electrospray ionization tandem mass spectrometry. All the anthocyanins were exclusively cyanidins or peonidin 3‐sophoroside‐5‐glucosides and their acylated derivatives. The total anthocyanin content in purple sweet potato powder obtained by solid‐phase extraction was 66 mg g^?1. A strong capacity of purple sweet potato anthocyanins (PSPA) to scavenge reactive oxygen species (superoxide, hydroxyl radical) and the stable 1,1‐diphenyl‐2‐picrylhydrazyl organic free radical was found in vitro using the electron spin resonance technique. To determine the functional roles of anthocyanins in leaves in vivo, for the first time, supplemental anthocyanins were infiltrated into leaves of Arabidopsis thaliana double mutant of the ecotype Landsberg erecta (tt3tt4) deficient in anthocyanin biosynthesis. Chlorophyll fluorescence imaging showed that anthocyanins significantly ameliorated the inactivation of photosystems II during prolonged high‐light (1300 µmol m^?2 s^?1) exposure. Comet assay of DNA revealed an obvious role of supplemental PSPA in alleviating DNA damage by high light in leaves. Our results suggest that anthocyanins could function in vitro and in vivo to alleviate the direct or indirect oxidative damage of the photosynthetic apparatus and DNA in plants caused by high‐light stress.     

Composition and desiccation-induced alterations of the cell wall in the resurrection plant Craterostigma wilmsii

Resurrection plants have the unique capacity to revive from an air-dried state. In order to tolerate desiccation they have to overcome a number of stresses, mechanical stress being one. In leaves of the Craterostigma species, an extensive shrinkage occurs during drying as well as a considerable cell wall folding. Our previous microscopically analysis using immunocytochemistry on the resurrection plant Craterostigma wilmsii , has shown an increase in labelling of xyloglucan and unesterified pectins in the cell wall during drying. In this study, we have undertaken a biochemical approach to separate, quantify and characterize major cell wall polysaccharides in fully hydrated and dry leaves of C. wilmsii . Our results show that the overall cell wall composition of C. wilmsii leaves was similar to that of other dicotyledonous plants with respect to the pectin content. However, the structure of the hemicellulosic polysaccharide xyloglucan was characterized to be XXGG-type. The data also demonstrate marked changes in the hemicellulosic wall fraction from dry plants compared to hydrated ones. The most conspicuous change was a decrease in glucose content in the hemicellulosic fraction of dry plants. In addition, xyloglucan from the cell wall of dry leaves was relatively more substituted with galactose than in hydrated walls. Together these findings show that dehydration induces significant alteration of polysaccharide content and structure in the cell wall of C. wilmsii , which in turn might be involved in the modulation of the mechanical properties of the wall during dehydration.     

Photosensitivity of seedlings differing in their potential to synthesize anthocyanin

In the present report the suggestion (Paech, K. 1950. Biochemie und Physiologie der sekundären Pflanzenstoffe. - Springer, Berlin, pp. 201–203) was tested that the photosynthetic apparatus requires light protection during the early phase of its development and that this is the reason (in a teleonomic sense) for the transient formation of large amounts of juvenile anthocyanin in outer tissue layers of seedlings and young leaves of deciduous trees and shrubs. Seedlings of two species ( Sinapis alba L. and Sesamum indicum L.) which differ in their potential to produce anthocyanin were compared under identical light conditions. The results obtained are compatible with the idea that juvenile anthocyanins are involved in photoprotection. However, the experimental results also indicate that full photostability of the plastid is attained - irrespective of the presence or absence of anthocyanin - once a certain amount of chlorophyll has been accumulated. Thus, photosensitivity of a seedling under natural light conditions is restricted to an early phase of development prior to intense greening.     

不同叶色红栌叶片中色素含量、酶活性及内含物差异的研究

为明确秋季不同叶色美国红栌叶片的生理差异,以秋季同一植株上红色、中间色、绿色三种颜色的美国红栌叶片为试材,测定了叶片中色素物质含量、酶活性以及叶片可溶性内含物的含量,结果表明：在红色叶片中,叶绿素含量较低,PAL、POD酶活性较高,花青素苷/叶绿素的比值较大,从而使叶色显现红色;而在绿色叶片中,叶绿素含量较高,PAL、POD酶活性较小,花青素苷/叶绿素的比值较低,叶片显现绿色。通过可溶性内含物测定可知,在红色叶片中的可溶性糖和蛋白质含量相对较高,均与花青素苷/叶绿素的比值达到显著相关水平,表明这些内含物的积累有利于花色素苷的合成。     

Desiccation-tolerant Sporobolus stapfianus: lipid composition and cellular ultrastructure during dehydration and rehydration

The desiccation-tolerant plant Sporobolus stapfianus was subjectedto slow dehydration and to rehydration either as a silica gel-drieddetached leaf or as an airdried plant. In detached leaves dehydrationresulted in a lower relative water content in comparison withleaves dried on the plant. Water loss caused a reduction inchlorophyll, carotenoid and lipid contents and an increase inconjugated dienes. In detached leaves, ultrastructure was alsoaffected by dehydration, showing damaged cells with alteredchloroplasts which retained large quantities of starch and lipid-likeinclusions in the stroma. Upon rehydration a continuous degradationof the chemical composition and cell organization was observedwith a further increase in peroxidation. Leaves dehydrated onthe plant showed degradation of chlorophyll and lipids, whereascarotenoids increased and conjugated dienes decreased. Desiccationcaused a vacuolar fragmentation and a decline in starch, whereaschloroplasts underwent slight alterations. Following rewateringa full recovery of chlorophyll and lipids occurred, while carotenoidsand dienes remained constant. Starch increased in the chloroplastsand there was complete recovery of the ordered cell arrangementand chloroplast organization. Of the chloroplast polar lipids,in both sets of leaves desiccation caused a reduction only inmonogalactosyldiacylglycerol, while phospholipids showed anopposite pattern, increasing in air-dried leaves and decreasingin detached leaves. Rewatering of leaves desiccated on the plantled to a complete recovery of the lipid composition, whereasdetached leaves suffered a complete lipid degradation with theloss of polyunsaturated fatty acids. Key words: Desiccation tolerance, lipids, resurrection plants, Sporobolus stapfianus, ultrastructure