Higher Stomatal Density Research Articles

Leaf anatomy of cultivated vine plants in cultivation environments and altitude regions

Plants can develop anatomical variations depending on the cultivation environment, and such characteristics can influence their physiology and significantly alter their capacity. The aim of the study was to evaluate the anatomical characteristics of the leaves of ‘Niágara Rosada’ grape varieties grown in different growing environments and different regions in the 2019/20 production cycle. An experiment was carried out in three cultivation conditions (full sun, under canvas and under plastic) in the region of Lages-SC. Another test was conducted in orchards with crops under full sun, in the regions of Lages-SC and Caçador-SC, altitudes of 1100 and 900 m, respectively. The variables analyzed were: stomatal density and stoma size, plant production and average cluster mass and chlorophyll index. In the first experiment, higher stomatal density was observed in plants grown in full sun compared to plants under canvas and greater stomatal area in plants grown under plastic in relation to the other conditions. The chlorophyll index was higher in plants grown under canvas, with no differences for plants grown under plastic. Plants grown under plastic showed higher production and average mass of clusters compared to plants grown under canvas and full sun. The stomatal density of vines produced in Caçador is higher than vines produced in Lages. The cultivation of vines under plastic cover is very advantageous in several aspects, such as: increased production and also protects against natural events, such as hail.

Intraspecific differences in plant functional traits are related to urban atmospheric particulate matter

BackgroundFunctional trait-based ecological research has been instrumental in advancing our understanding of environmental changes. It is still, however, unclear how the functional traits of urban plants respond to atmospheric particulate matter, and which trade-off strategies are shown. In order to explore the variation of plant functional traits with the gradient of urban atmospheric particulate matter, we divided atmospheric particulate matter into three levels according to road distance, and measured the variation of six essential leaf functional traits and their trade-off strategies.ResultsHere, we show that the functional traits of plants can be used as predictors of plant response to urban atmospheric particulate matter. Within the study, leaf thickness, leaf dry matter content, leaf tissue density, stomatal density were positively correlated with atmospheric particulate matter. On the contrary, chlorophyll content index and specific leaf area were negatively correlated with atmospheric particulate matter. Plants can improve the efficiency of gas exchange by optimizing the spatial distribution of leaf stomata. Under the atmospheric particulate matter environment, urban plants show a trade-off relationship of economics spectrum traits at the intraspecific level.ConclusionUnder the influence of urban atmospheric particulate matter, urban plant shows a “slow investment-return” type in the leaf economics spectrum at the intraspecific level, with lower specific leaf area, lower chlorophyll content index, ticker leaves, higher leaf dry matter content, higher leaf tissue density and higher stomatal density. This finding provides a new perspective for understanding the resource trades-off strategy of plants adapting to atmospheric particulate matter.

Hydraulic-stomatal coordination in tree seedlings: tight correlation across environments and ontogeny in Acer pseudoplatanus.

Hydraulic conductance is recognized as a major determinant of gas exchange and productivity. However, whether this also applies to seedlings, a critically important stage for vegetation regeneration, has been largely unknown. We analyzed the hydraulic and stomatal conductance of leaves and shoots for 6-wk-old Acer pseudoplatanus seedlings emerging in different lowland and treeline habitats and under glasshouse conditions, respectively, as well as on 9-, 15- and 18-wk-old plants, and related findings to leaf and xylem anatomical traits. Treeline seedlings had higher leaf area-specific shoot hydraulic conductance (Kshoot-L ), and stomatal conductance (gs ), associated with wider xylem conduits, lower leaf area and higher stomatal density than lowland and glasshouse-grown plants. Across the first 18 wk of development, seedlings increased four-fold in absolute shoot hydraulic conductance (Kshoot ) and declined by half in Kshoot-L , with correlated shifts in xylem and leaf anatomy. Distal leaves had higher leaf hydraulic conductance (Kleaf ) and gs compared to basal leaves. Seedlings show strong variation across growth environments and ontogenetic shifts in hydraulic and anatomical parameters. Across growth sites, ontogenetic stages and leaf orders, gs was tightly correlated with Kshoot-L and Kleaf , balancing hydraulic supply with demand for the earliest stages of seedling establishment.

The effect of organic fertilizers on the leaf morphology and stomatal density of Pogostemon cablin Benth

Pogostemon cablin Benth is one of the most important crops grown in Indonesia, especially in Aceh province. It is well known as Patchouli belongs to Lamiaceae family and shows a great demand for perfume, luxury products, food and beverage industry. This study conducted to determine the effect of organic fertilizers application on the leaf morphology and stomatal density on the Pogostemon cablin Benth. The seedlings were transplanted for three months on the soil mixed either with manure or compost. The results obtained that was no significant different in affecting the leaf morphology of Pogostemon cablin Benth. The treatment with manure application showed the highest leaf length (15.23 cm) and the highest leaf width (10.5 cm), the leaf color is green. While the stomatal density obtained the significant difference among the treatments, the highest stomatal density in both side of the leaf surface showed in the application of manure, 663.5 mm-2 for adaxial part and 486.38 mm-2 for abaxial part. Stomatal type is anisocytic and on the leaf surface was found glandular and non-glandular trichomes.

Morphophysiological characters of binahong (Anredera cordifolia (L.) Steenis) with application of natural growth regulators

The morphophysiological study of binahong is still limited. The objective of the research is to identify the morphophysiological characteristics of binahong plants through natural GR application. This study described the relationship of plant length, number of leaves, stomatal density, and the content of chlorophyll leaves of binahong due to the application of natural growth regulators from coconut water combined with red shallot extract, bamboo shoots, and banana weevils. The research used a nonfactorial randomized block design with 3 replications. The results obtained in general giving GR can reduce plant length and number of leaves. The highest stomatal density was obtained in the application of coconut water while the lowest as shown in the application of coconut water and bamboo shoots. Chlorophyll a and b, as well as the highest total chlorophyll, are found without growth regulators application and application of a mixture of coconut water, shallot, bamboo shoots and, banana weevils. Chlorophyll a and b and the lowest total chlorophyll are found in the application of coconut water and bamboo shoots.

Physiological and anatomical changes in two rapeseed (Brassica napus L.) genotypes under drought stress conditions

Understanding the mechanisms of drought resistance in crop species is crucial for the selection and breeding of tolerant rapeseed (Brassica napus L.) varieties. The present study aimed to assess the physiological and anatomical responses of two rapeseed genotypes, P287 (drought-tolerant) and T88 (drought-sensitive) under three intensities of drought stress. All physiological and anatomical parameters related to drought acclimation were significantly altered in both genotypes under stress conditions. At the fourth-leaf stage, the relative water content, chlorophyll content, protein content, malondialdehyde content, and the activities of peroxidase and catalase in P287 were significantly higher than those in T88, particularly under severe drought conditions. After rehydration, all physiological indexes recovered rapidly, especially in P287. In addition, under drought stress, compared with T88, P287 had thicker palisade tissue, thinner spongy tissue, higher ratio of chloroplast length to chloroplast width, higher stomatal density and stomatal closure rate. Overall, the interaction between physiological and anatomical features improved the drought tolerance of P287 under drought stress conditions.

Leaves of more cold hardy grapes have a higher density of small, sunken stomata

Leaf stomatal density, index and size are known to be affected by the growing conditions, presumably to provide a better function for plant development. The question was whether there is a difference in stomatal parameters between grape species with different cold hardiness: V. riparia and V. vinifera; and the V. vinifera cultivars 'Riesling', 'Chardonnay', 'Sauvignon Blanc' and 'Merlot'. Analysis by scanning electron microscopy allowed the observation of 3 types of stomata in developing and mature leaves of all examined grape leaves. Stomatal parameters were found to be significantly affected by species or cultivar and growing conditions but not rootstock. A higher stomatal density and index were determined for the more cold hardy V. riparia and V. vinifera 'Riesling', whereby the higher number of stomata in 'Riesling' was found to be due to a higher number of small, sunken stomata. These findings might indicate a strategy of grape plants to optimize growth under low temperatures by using fast-acting stomata whose gas and water exchange are less affected than for larger stomata.

LED and HPS Supplementary Light Differentially Affect Gas Exchange in Tomato Leaves.

Using light emitting diodes (LED) instead of conventionally used high pressure sodium (HPS) lamps as a supplemental light source in greenhouses results in a higher efficacy (µmol light per J electricity) and makes it possible to customize the light spectrum. To explore the effects of LED and HPS on gas exchange, thermal relations, photosynthesis, and water status of young tomato plants, seven genotypes were grown in a greenhouse under LED (95% red, 5% blue) or HPS lamps in four experiments differing in the fraction of lamp light over natural light. HPS lights emit a broader spectrum of red (40%), green–yellow (50%), blue (5%), and far-red (5%) and a substantial amount of infrared radiation (heat). Young tomato plants grown under LED showed lower leaf temperature and higher stomatal density, stomatal conductance (gs) and transpiration rate (E) than plants grown under HPS; this may be due to the different supplemental light spectrum. The young plants grown under LED tended to have increased photosynthetic capacity. Furthermore, the water stress indices CWSI and IG, which were obtained using thermal imaging, were positively correlated with gas exchange-derived gs and E, putting forward the use of thermal imaging for the phenotyping of transpiration. Under LED light, photosynthetic gas exchange was generally increased, which agreed with the water stress indices. The extent of this increase was genotype-dependent. All differences between LED and HPS were smaller in the experiments where the fraction of lamp light over natural light was smaller.

Changes in Physiological and Relative Genes Expression Response of Mandarin Citrus (Citrus reticulata Blanco) cv Rimau Gerga Lebong (RGL) Grafted onto Different Citrus Rootstocks

Background: RGL mandarin is one of the important mandarin citrus varieties in Indonesia. The tolerance of RGL mandarin citrus to water deficit can be induced by the rootstock. This study aimed to characterize the physiological responses and transcriptional gene expression of RGL mandarin citrus grafted onto three rootstock genotypes during the dry and the rainy seasons.Methods: Three-years-old mandarin citrus trees cv. Rimau Gerga Lebong (RGL) grafted onto three citruses (JC, Cit and K) were planted at the experimental field of the ICISFRI. The experiment was conducted with a randomized block design and each scion-rootstock combination contained five replications. All of the physiological and relative gene expression parameters observed were conducted at the last of the dry season (September 2019) and the mid of the rainy season (January 2020). Water deficit was induced by no watering plants during the dry season.Result: The results of physiological responses and relative gene expression analyses showed that RGL-Cit combination had better than RGL-JC combination and RGL-JC combination had better than RGL-K combination. RGL-Cit combination showed less wilt than RGL-JC and RGL-K combinations. The RGL-Cit combination had the highest stomatal density, stomatal aperture, stomatal conductance and photosynthetic rate in the dry season. Different plant combinations showed different gene expressions. RGL-JC and RGL-K combinations were upregulated in almost all the primers related to drought responses tested in the dry season. RGL-Cit combination only upregulated the PIP1, PIP2 and ACS2 and unregulated the others in the dry season. Therefore, citrumelo seems to be a valuable type of rootstock.

Influence of Plant Physical and Anatomical Characteristics on the Ovipositional Preference of Orius sauteri (Hemiptera: Anthocoridae).

Simple SummaryThe minute pirate bug Orius sauteri is the predator of many soft-body pests and has great application prospect in pest suppression in Asia. Females need to insert their ovipositor into plant tissues to lay eggs. Thus, understanding its egg-laying preferences and creating it a beneficial habitat is important for its conversation in the field. We evaluated the ovipositional preference of the females for four noncrop plant species and how the plant characteristics influenced the ovipositional behavior of O. sauteri. Our results suggested that O. sauteri females were able to select oviposition host and specific sites through assessing the structural qualities of plants. Females were found to prefer plants with high stomatal density, a large stomatal area, and fewer trichomes as oviposition hosts, and the depth of egg placement was determined by leaf thickness. Coriander and marigold are potential oviposition plants for O. sauteri for high fecundity and egg hatchability. The results are helpful for selecting beneficial cover crops to natural enemies in the field and lead to a positive outcome for biological control.Natural enemies play an important role in managing insect pests. Orius sauteri (Poppius) (Hemiptera: Anthocoridae), a predator of many soft-body insects, is an important biological control agent in Asia. Understanding this predator’s egg-laying preferences and a habitat needs is important for its success in pest control. We investigated the plant acceptability and ovipositional preference of O. sauteri for coriander (Coriadrum sativum L., Apiales: Apiaceae), marigold (Tagetes erecta L., Asterales: Asteraceae), sweet alyssum (Lobularia maritima L., Brassicales: Brassicaceae), and alfalfa (Medicago sativa L., Fabales: Fabaceae), and focused on the effects of plant physical and anatomical characteristics on the ovipositional preference of O. sauteri. The results showed that O. sauteri can lay eggs on uninfested plants in the vegetative stage and their eggs hatched normally. Orius sauteri females prefer plants with high stomatal density, a large stomatal area, and fewer trichomes as oviposition hosts, and the depth of egg placement was determined by leaf thickness. Our studies suggested that O. sauteri females can select oviposition hosts and specific oviposition sites by assessing the structural qualities of plant surface. Coriander and marigold are potentially suitable host plants for O.sauteri. The results aid the selection of cover crops to enhance natural enemies in the fields.

Functional differentiation among 12 dipterocarp species under contrasting water availabilities in Northeast Thailand

Species composition varies greatly dependent on water availability gradients. In Northeast Thailand, dry deciduous forests (DDF) and dry evergreen forests (DEF) show contrasting species composition due to differences in soil structure and moisture. Although plant traits (physiological and morphological characteristics) are known to be involved in species distributions, which traits underpin these distinct distributions (either dry DDF or less-dry DEF) remain unclear. Here, we examined the differentiation of 21 leaf and stem traits between DDF and DEF using 12 dipterocarp species. We found that DDF species showed higher water use efficiency and higher water storage capacity in the lamina and petiole, higher leaf nitrogen content, higher stomatal density, larger leaves, thicker mesophyll layers, and a higher rate of water loss under severe dehydration than DEF species. Leaf osmotic potential at full turgor, wood density, and wood water content were not significantly different between DDF and DEF. We also observed a negative relationship between the potential photosynthetic capacity and the water loss rate during severe dehydration across species. Our results suggest that the differences in leaf traits related to photosynthesis and dehydration avoidance among the tree species produce niche differences along the soil water availability in tropical dry forests.

Leaf morphoanatomy of an endemic massaranduba from Chapada Diamantina, Bahia, Brazil

Abstract: The Sapotaceae family is recognized for its economic importance, presenting food, medicinal and timber potential. Pouteria andarahiensis T.D.Penn., popularly known as "massaranduba", is endemic to Chapada Diamantina, Bahia, Brazil, and is currently classified on the IUCN red list as "endangered". Pouteria andarahiensis is little studied, highlighting this work as the first anatomical study for the species. Light microscopy and scanning electron microscopy techniques were used to perform anatomical studies. The species showed characters shared with the family (laticifers and malpiguiaceous trichomes), as well as diagnostic characters and associated with xeromorphy. The data obtained from the leaf architecture can assist in the identification of the species in a vegetative state, while the leaf surface provided unpublished data to the species, indicating the presence of a cuticle with complex ornamentation. Stand out as xeromorphic anatomical features, high stomatal density, high number of trichomes per area, sclerenchymatic columns in the mesophyll and a subepidermal sclerenchyma layer connecting the vascular bundles in the mesophyll.

Ecophysiological response of Astronium fraxinifolium (Anacardiaceae) in degraded and non-degraded brazilian Cerrado

Abstract Plants native from Cerrado generally have peculiar characteristics that allow tolerating water and nutritional stress. Astronium fraxinifolium is a Anacardiaceae tree of from Brazilian Cerrado. The aim of this research was to characterize A. fraxinifolium leaves morphophysiologically, in order to recognize characteristics related to acclimatization of the species in different soil conditions. Two populations of A. fraxinifolium were sampled in different study areas, A1 (Degraded Soil) and A2 (“Undegraded Soil”). Nitrogen compounds, total carbohydrates, chlorophyll, nutritional content, stomatal density and gas exchanges were quantified, comparing the areas. A high number of stomata was observed on the abaxial surface of A. fraxinifolium leaves, with a higher density occurring in A1 individuals. The values of chlorophyll and boron content were significantly higher in A2 plants. It’s possible that the lowest concentration of boron in A1 plants is related to chlorophyll production. Regardinf the other analysis, there weren’t significant differences between the areas. The results show that this species undergoes changes in production of chlorophyll, but liquid photosynthesis isn’t impaired, considering the low chlorophyll content in A1 being compensated by the higher stomatal density. Thus, these changes may be the result of acclimating this species to different environmental conditions to which it’s exposed.

Adaptive trait syndromes along multiple economic spectra define cold and warm adapted ecotypes in a widely distributed foundation tree species

Abstract The coordination of traits from individual organs to whole plants is under strong selection because of environmental constraints on resource acquisition and use. However, the tight coordination of traits may provide underlying mechanisms of how locally adapted plant populations can become maladapted because of climate change. To better understand local adaptation in intraspecific trait coordination, we studied trait variability in the widely distributed foundation tree species, Populus fremontii using a common garden near the mid‐elevational point of this species distribution. We examined 28 traits encompassing four spectra: phenology, leaf economic spectrum (LES), whole‐tree architecture (Corner's Rule) and wood economic spectrum (WES). Based on adaptive syndrome theory, we hypothesized that trait expression would be coordinated among and within trait spectra, reflecting local adaptation to either exposure to freeze‐thaw conditions in genotypes sourced from high‐elevation populations or exposure to extreme thermal stress in genotypes sourced from low‐elevation populations. High‐elevation genotypes expressed traits within the phenology and WES that limit frost exposure and tissue damage. Specifically, genotypes sourced from high elevations had later mean budburst, earlier mean budset, higher wood densities, higher bark fractions and smaller xylem vessels than their low‐elevation counterparts. Conversely, genotypes sourced from low elevations expressed traits within the LES that prioritized hydraulic efficiency and canopy thermal regulation to cope with extreme heat exposure, including 40% smaller leaf areas, 67% higher stomatal densities and 34% higher mean theoretical maximum stomatal conductance. Low‐elevation genotypes also expressed a lower stomatal control over leaf water potentials that subsequently dropped to pressures that could induce hydraulic failure. Synthesis. Our results suggest that Populus fremontii expresses a high degree of coordination across multiple trait spectra to adapt to local climate constraints on photosynthetic gas exchange, growth and survival. These results, therefore, increase our mechanistic understanding of local adaptation and the potential effects of climate change that in turn, improves our capacity to identify genotypes that are best suited for future restoration efforts.

Plasticidade dos estômatos em folhas de Ichthyothere terminalis (Spreng) Blake (Asteraceae) em diferentes estações do ano

O Cerrado possui a flora diversificada que ocorre em diferentes fisionomias. Uma das características marcantes do bioma é a ocorrência de estações chuvosa e seca bem definidas. Durante a seca as plantas do Cerrado estão sujeitas à restrição de água. Os estômatos, que são estruturas epidérmicas responsáveis pelas trocas gasosas, são essenciais para a manutenção do estado hídrico das plantas. Ichthyothere terminalis (Spreng.) Blake é uma Asteraceae herbácea frequente nas formações abertas do Cerrado. A espécie possui sistema subterrâneo espessado, que contribui para persistência da planta no ambiente. No final da seca, ocorre a rebrota dos órgãos aéreos. O objetivo deste trabalho foi o de avaliar as dimensões dos estômatos em folhas de Ichthyothere terminalis em diferentes épocas do ano. Foram realizadas coletas em fisionomias abertas do Cerrado em períodos secos e chuvosos, nos quais as plantas estavam em diferentes fases fenológicas. As folhas foram coletadas, preservadas e fixadas seguindo métodos usuais para análises anatômicas e histométricas. As epidermes foram destacadas e as medições e contagens foram feitas em microscópio de luz. As folhas de Ichthyothere terminalis são anfiestomáticas, com maior densidade estomática na face abaxial. A densidade de estômatos na face abaxial foi maior na transição entra as estações seca e chuvosa. A área dos poros estomáticos foi maior no início da seca nas duas faces epidérmicas. A espécie mostrou capacidade de alterar os atributos dos estômatos em diferentes estações, e isso pode contribuir para sua ocorrência em habitats sujeitos à seca sazonal.

Counter-Intuitive Response to Water Limitation in a Southern European Provenance of Frangula alnus Mill. in a Common Garden Experiment

Climate change will intensify drought periods during the growing season in Western Europe. We mimicked this prediction by withholding water in summer from young rooted cuttings of Frangula alnus Mill., a common shrub species, originating from different latitudes in Europe (Italy, Belgium and Sweden) and growing in a common garden environment in Belgium. We followed the responses to the drought up to two years after the treatment. Counter-intuitively, the Italian provenance displayed earlier symptoms and stronger effects of water limitation than the other two provenances. A putative higher transpiration in this provenance could be suggested based on a relative larger shoot growth, larger leaves and a higher stomatal density. After the post-drought re-watering, the droughted plants of the Italian provenance entered leaf senescence later than the control plants, likely as a compensation mechanism for the lost growing time. Bud burst in the first year after the drought treatment and leaf senescence in the next autumn were both advanced in the drought treated group when compared with the control plants. Bud burst in the second year after the drought treatment did not display any differentiation anymore between control and drought treated plants. Growth traits also displayed legacies of the water limitation. For example, the drought treated plants showed a lower number of reshoots upon pruning in the year after the drought treatment. Our results suggest that assisted migration from southern Europe to western Europe as a climate change adaptation strategy might not always follow the expected patterns.

Physio-morphological, biochemical, and anatomical traits of drought-tolerant and susceptible sorghum cultivars under pre- and post-anthesis drought.

Understanding the physiological mechanisms that control drought tolerance in crop plants is vital for effective breeding. In this study, we characterized drought stress responses in four sorghum cultivars exhibiting differential levels of drought tolerance at pre- and post-anthesis. Greenhouse-grown plants were subjected to two types of drought treatment, water stress (WS) and desiccant-induced water stress (DA), timed to occur at pre- and post-anthesis. Multiple physiological measurements were then made revealing varying responses among the experimental cultivars. The pre- and post-flowering drought-tolerant cultivar P898012 showed a significantly higher net photosynthetic rate, higher transpiration rate, and greater stomatal conductance compared to the drought-susceptible cultivars at both pre- and post-anthesis. A significantly greater stomatal size was also detected in P898012, while the highest stomatal density was found in the drought-susceptible cultivar P721Q. Meanwhile, the two post-flowering drought-tolerant cultivars P898082 and B35 had a higher starch content and exhibited greater osmotic potential under post-anthesis water stress. Compared to WS and well-watered control plants, a greater increase in root biomass was observed in P898012 under DA at pre-anthesis. This finding suggests that plants invested more assimilates into the roots under severe DA at pre-anthesis. Overall, our results show good conformity between drought tolerance in sorghum and key physiological mechanisms of stomatal conductance, root growth patterns, and starch accumulation, all of which act as coping mechanisms during critical drought-sensitive growth stages.

Light quality affects the proliferation of in vitro cultured plantlets of Camellia oleifera Huajin.

BackgroundCamellia oleifera is an important oil-yielding woody plant native to China. Tea oil extracted from the seeds is rich in health-beneficial compounds. Huajin is a high-yielding elite variety of C. oleifera, with large fruits and remarkable resilience, widely cultivated in southern China; however, its seedling quality tends to be uneven. At present, techniques such as grafting, and cuttings are primarily adopted to propagate C. oleifera. These approaches are susceptible to environmental constraints owing to the long growth period, resulting in the lack of C. oleifera seedlings. Methods to make the cultivation more economical are warranted; this can be facilitated by tissue culture technology to provide good-quality seedlings in a short time.MethodsIn vitro cultured plantlets of C. oleifera Huajin were exposed to red light (RL), blue light (BL), red:blue light at a 4:1 ratio (R4:B1), and red:blue light at a 1:4 ratio (R1:B4); white light (WL) was used as the control treatment. To investigate the influence of light spectral quality on the proliferation coefficient, photosynthetic pigments, soluble proteins, plant height, leaf shape, Rubisco enzyme activity, and stomata and leaf anatomical features.ResultsThe highest proliferation coefficient was observed under combined red and blue (4:1) light. In addition, this treatment resulted in the second highest chlorophyll content, the thickest palisade and spongy tissues, and consequently, the thickest leaves. The same treatment resulted in the second highest stomatal density, albeit concomitantly with the smallest average stomatal length and width.DiscussionThese results indicate that high-quality propagation of Huajin shoots can be achieved by culturing the plants in vitro under a combination of red and blue (4:1) lights. Previous studies have shown that red and blue lights improve rooting and transplanting rates of tissue culture seedlings. Hence, future research should focus on the effect of light quality on rooting and transplanting of tissue culture plantlets of Huajin and its specific molecular mechanisms.

Stomatal density and mechanics are critical for high productivity: insights from amphibious ferns.

Angiosperm dominance in terrestrial landscapes is partially attributable to high photosynthetic capacities. Angiosperms benefit from diverse anatomical and physiological adaptations, making it difficult to determine which factors may have been prerequisites for the evolution of enhanced photosynthetic rates in this group. We employed a novel approach to this problem: comparisons between angiosperms and Marsileaceae, a family of semi-aquatic ferns that are among the only land plants to match angiosperm photosynthetic rates. We found that Marsileaceae have very high stomatal densities and, like angiosperms but unlike all other ferns previously studied, exhibit wrong-way stomatal responses to excision. These results suggest that stomatal density and a little-studied angiosperm trait, the capacity for lateral displacement of guard cells into neighboring epidermal cells, are crucial for facilitating high rates of gas exchange. Our analysis also associates these adaptations in Marsileaceae with an increased risk of excessive water loss during drought. Our findings indicate that evolution in stomatal physiology was a prerequisite for high photosynthetic capacities in vascular plants and a key driver of the abrupt Cretaceous rise of the angiosperms.

The interplay between irrigation and fruiting on branch growth and mortality, gas exchange and water relations of coffee trees.

The overall coordination between gas exchanges and plant hydraulics may be affected by soil water availability and source-to-sink relationships. Here we evaluated how branch growth and mortality, leaf gas exchange and metabolism are affected in coffee (Coffea arabica L.) trees by drought and fruiting. Field-grown plants were irrigated or not, and maintained with full or no fruit load. Under mild water deficit, irrigation per se did not significantly impact growth but markedly reduced branch mortality in fruiting trees, despite similar leaf assimilate pools and water status. Fruiting increased net photosynthetic rate in parallel with an enhanced stomatal conductance, particularly in irrigated plants. Mesophyll conductance and maximum RuBisCO carboxylation rate remained unchanged across treatments. The increased stomatal conductance in fruiting trees over nonfruiting ones was unrelated to internal CO2 concentration, foliar abscisic acid (ABA) levels or differential ABA sensitivity. However, stomatal conductance was associated with higher stomatal density, lower stomatal sensitivity to vapor pressure deficit, and higher leaf hydraulic conductance and capacitance. Increased leaf transpiration rate in fruiting trees was supported by coordinated alterations in plant hydraulics, which explained the maintenance of plant water status. Finally, by preventing branch mortality, irrigation can mitigate biennial production fluctuations and improve the sustainability of coffee plantations.