Effects of Salt Stress on the Leaf Shape and Scaling of Pyrus betulifolia Bunge

Surviving the desert's grasp: Decipherment phreatophyte Tamarix aphylla (L.) Karst. Adaptive strategies for arid resilience

Phreatophytes play an important role in maintaining the ecological services in arid and semi-arid areas. Characterizing the interaction between groundwater and phreatophytes is critical for the land and water management in such areas. Therefore, the identification of key traits related to mitigating desertification in differently adapted T. aphylla populations was the focus. Fifteen naturally adapted populations of the prominent phreatophyte T. aphylla from diverse ecological regions of Punjab, Pakistan were selected. Key structural and functional modifications involved in ecological success and adaptations against heterogeneous environments for water conservation include widened metaxylem vessels in roots, enlarged brachy sclereids in stems/leaves, tissues succulence, and elevated organic osmolytes and antioxidants activity for osmoregulation and defense mechanism. Populations from hot and dry deserts (Dratio: 43.17-34.88) exhibited longer roots and fine-scaled leaves, along with enlarged vascular bundles and parenchyma cells in stems. Populations inhabiting saline deserts (Dratio: 38.59-33.29) displayed enhanced belowground biomass production, larger root cellular area, broadest phloem region in stems, and numerous large stomata in leaves. Hyper-arid populations (Dratio: 33.54-23.07) excelled in shoot biomass production, stem cellular area, epidermal thickness, pith region in stems, and lamina thickness in leaves. In conclusion, this research highlights T. aphylla as a vital model for comprehending plant resilience to environmental stresses, with implications for carbon sequestration and ecosystem restoration.

Leaf functional traits of Parrotia subaequalis from different environments in eastern China

Functional traits are important in understanding how plants respond and adapt to their immediate environment. Parrotia subaequalis is a highly endangered arbor species found throughout eastern China, primarily inhabiting hillsides and valleys, yet, little is known about the variation in leaf traits across these environments. In the present study, we tested this by comparing leaf surface area, leaf weight, leaf length, leaf symmetry and leaf mass per unit area, as well as the relationship between leaf traits and environmental factors and the scaling relationship between leaf surface area versus leaf dry mass. We observed significant differences in leaf surface area, weight, and length among the population sites, and these variables were strongly affected by environmental factors, especially high mean annual temperatures in hillside habitats and high mean annual precipitation in valley habitats. The scaling exponents remained numerically variant among the 10 populations, with different slopes greater than 1.0, and the scaling exponents increased significantly with hillside habitats. These metrics correlated with soil thickness associated with different habitat types. The areal ratio (AR) values in all populations deviated from 1, indicating that the two lamina sides were asymmetrical. The standardized symmetry index (SI) values displayed significant variation, especially in leaves from hillside habitats with a high degree of asymmetry. Collectively, our findings demonstrated that leaf functional traits exhibit considerable variability in response to different environmental contexts and provide valuable reference data that could be useful for conserving this endangered species.

Phytoremediation through microstructural and functional alterations in alkali weed (Cressa cretica L.) in the hyperarid saline desert

Salt excretory halophytes are the major sources of phytoremediation of salt-affected soils. Cressa cretica is a widely distributed halophyte in hypersaline lands in the Cholistan Desert. Therefore, identification of key physio-anatomical traits related to phytoremediation in differently adapted C. cretica populations was focused on. Four naturally adapted ecotypes of non-succulent halophyte Cressa cretica L. form hyper-arid and saline desert Cholistan. The selected ecotypes were: Derawar Fort (DWF, ECe 20.8 dS m-1) from least saline site, Traway Wala Toba (TWT, ECe 33.2 dS m-1) and Bailah Wala Dahar (BWD, ECe 45.4 dS m-1) ecotypes were from moderately saline sites, and Pati Sir (PAS, ECe 52.4 dS m-1) was collected from the highly saline site. The natural population of this species was collected and carefully brought to the laboratory for different structural and functional traits. As a result of high salinity, Na+, Cl-, K+, and Ca2+ content significantly increased at root and shoot level. At root level, some distinctive modifications such as increased sclerification in vascular bundles, enlarged vascular bundles, metaxylem vessels, phloem region, and storage parenchyma (cortex) are pivotal for water storage under extreme arid and osmotic condition. At the stem level, enhanced sclerification in outer cortex and vascular bundles, stem cellular area, cortical proportion, metaxylem and phloem area, and at the leaf level, very prominent structural adaptations were thicker and smaller leaves with increased density of salt glands and trichomes at surface, few and large stomata, reduced cortical and mesophyll parenchyma, and narrow xylem vessels and phloem area represent their non-succulent nature. The ecotype collected from hypersaline environments was better adapted regarding growth traits, ion uptake and excretion, succulence, and phytoremediation traits. More importantly, structural and functional traits such as root length and biomass, accumulation of toxic ions along with K+ in root and shoot, accumulation of Ca2+ in shoot and Mg2+ in root, excretion of toxic ions were the highest in this ecotype. In conclusion, all these alterations strongly favor water conservation, which certainly contributes to ecotypes survival under salt-induced physiological drought.

Salt Tolerance Evaluation of Cucumber Germplasm under Sodium Chloride Stress

Cucumber (Cucumis sativus L.) is an important horticultural crop worldwide. Sodium (Na+) and chloride (Cl-) in the surface soil are the major limiting factors in coastal areas of Shandong Province in China. Therefore, to understand the mechanism used by cucumber to adapt to sodium chloride (NaCl), we analyzed the phenotypic and physiological indicators of eighteen cucumber germplasms after three days under 100 and 150 mM NaCl treatment. A cluster analysis revealed that eighteen germplasms could be divided into five groups based on their physiological indicators. The first three groups consisted of seven salt-tolerant and medium salt-tolerant germplasms, including HLT1128h, Zhenni, and MC2065. The two remaining groups consisted of five medium salt-sensitive germplasms, including DM26h and M1-2-h-10, and six salt-sensitive germplasms including M1XT and 228. A principal component analysis revealed that the trend of comprehensive scores was consistent with the segmental cluster analysis and survival rates of cucumber seedlings. Overall, the phenotype, comprehensive survival rate, cluster analysis, and principal component analysis revealed that the salt-tolerant and salt-sensitive germplasms were Zhenni, F11-15, MC2065, M1XT, M1-2-h-10, and DM26h. The results of this study will provide references to identify or screen salt-tolerant cucumber germplasms and lay a foundation for breeding salt-tolerant cucumber varieties.

The roles of WRKY transcription factors in Malus spp. and Pyrus spp

The WRKY transcription factor gene family is known to be involved in plant defense against pathogens and in tolerance to different environmental stresses at different stages of development. The response mechanisms through which these genes act can be influenced by different phytohormones as well as by many trans- and cis-acting elements, making this network an important topic for analysis, but still something complex to fully understand. According to available reports, these genes can also perform important roles in pome species (Malus spp. and Pyrus spp.) metabolism, especially in adaptation of these plants to stressful conditions. Here, we present a quick review of what is known about WRKY genes in Malus and Pyrus genomes offering a simple way to understand what is already known about this topic. We also add information connecting the evolution of these transcription factors with others that can also be found in pomes.

Versatile roles of sorbitol in higher plants: luxury resource, effective defender or something else?

Sorbitol metabolism plays multiple roles in many plants, including energy and carbon enrichment, effective defence against various stresses and other emerging specific roles. The underlying mechanisms are, however, incompletely understood. This review provides the current state-of-the-art, highlights missing knowledge and poses several remaining questions. The basic properties of sugar alcohols are summarised and pathways of sorbitol metabolism, including biosynthesis, degradation and key enzymes are described. Sorbitol transport within the plant body is discussed and individual roles of sorbitol in different organs, specific cells or even cellular compartments, are elaborated, clarifying the critical importance of sorbitol allocation and distribution. In addition to plants that accumulate and transport significant quantities of sorbitol (usual producers), there are some that synthesize small amounts of sorbitol or only possess sorbitol metabolising enzymes (non-usual producers). Modern analytical methods have recently enabled large amounts of data to be acquired on this topic, although numerous uncertainties and questions remain. For a long time, it has been clear that enriching carbohydrate metabolism with a sorbitol branch improves plant fitness under stress. Nevertheless, this is probably valid only when appropriate growth and defence trade-offs are ensured. Information on the ectopic expression of sorbitol metabolism genes has contributed substantially to our understanding of the sorbitol roles and raises new questions regarding sorbitol signalling potential. We finally examine strategies in plants producing sorbitol compared with those producing mannitol. Providing an in-depth understanding of sugar alcohol metabolism is essential for the progress in plant physiology as well as in targeted, knowledge-based crop breeding.

Cut Flower Characteristics and Growth Traits under Salt Stress in Lily Cultivars

Salt stress is a major constraint of crop productivity because it reduces yield and limits the expansion of agriculture. This study investigated salt tolerance in 26 cultivars of cut lilies (Lilium hybrids) by examining the effect of salt stress on the growth and morphological characteristics of flowers and leaves and their physiological properties (chlorophyll a fluorescence). Salt stress significantly affected the growth and development of cut lilies. Canonical discriminant analysis indicates that the middle leaf width, number of flowers, first flower diameter, petal width, and chlorophyll a fluorescence were correlated with salt stress, whereas plant height, the middle leaf length, days to flowering, and sepal width were less affected by the stress. The cultivars examined were divided into three groups: Group 1 included the salt-sensitive cultivars, which failed to develop normal flowers; Group 2 included cultivars sensitive to salt stress but tolerant to osmotic stress; and Group 3 was the salt-tolerant group, which developed commercially valuable flowers. In conclusion, the cultivars contained a variable range of cut flower characteristics and growth traits that can be employed for lily breeding programs and as material for molecular mechanisms and signaling networks under salt stress.

Leaf Bilateral Symmetry and the Scaling of the Perimeter vs. the Surface Area in 15 Vine Species

The leaves of vines exhibit a high degree of variability in shape, from simple oval to highly dissected palmatifid leaves. However, little is known about the extent of leaf bilateral symmetry in vines, how leaf perimeter scales with leaf surface area, and how this relationship depends on leaf shape. We studied 15 species of vines and calculated (i) the areal ratio (AR) of both sides of the lamina per leaf, (ii) the standardized symmetry index (SI) to estimate the deviation from leaf bilateral symmetry, and (iii) the dissection index (DI) to measure leaf-shape complexity. In addition, we examined whether there is a scaling relationship between leaf perimeter and area for each species. A total of 14 out of 15 species had no significant differences in average ln(AR), and mean ln(AR) approximated zero, indicating that the areas of the two lamina sides tended to be equal. Nevertheless, SI values among the 15 species had significant differences. A statistically strong scaling relationship between leaf perimeter and area was observed for each species, and the scaling exponents of 12 out of 15 species fell in the range of 0.49−0.55. These data show that vines tend to generate a similar number of left- and right-skewed leaves, which might contribute to optimizing light interception. Weaker scaling relationships between leaf perimeter and area were associated with a greater DI and a greater variation in DI. Thus, DI provides a useful measure of the degree of the complexity of leaf outline.

Scaling Relationships between Leaf Shape and Area of 12 Rosaceae Species

Leaf surface area (A) and leaf shape have been demonstrated to be closely correlated with photosynthetic rates. The scaling relationship between leaf biomass (both dry weight and fresh weight) and A has been widely studied. However, few studies have focused on the scaling relationship between leaf shape and A. Here, using more than 3600 leaves from 12 Rosaceae species, we examined the relationships of the leaf-shape indices including the left to right side leaf surface area ratio (AR), the ratio of leaf perimeter to leaf surface area (RPA), and the ratio of leaf width to length (RWL) versus A. We also tested whether there is a scaling relationship between leaf dry weight and A, and between PRA and A. There was no significant correlation between AR and A for each of the 12 species. Leaf area was also found to be independent of RWL because leaf width remained proportional to leaf length across the 12 species. However, there was a negative correlation between RPA and A. The scaling relationship between RPA and A held for each species, and the estimated scaling exponent of RPA versus A approached −1/2; the scaling relationship between leaf dry weight and A also held for each species, and 11 out of the 12 estimated scaling exponents of leaf dry weight versus A were greater than unity. Our results indicated that leaf surface area has a strong scaling relationship with leaf perimeter and also with leaf dry weight but has no relationship with leaf symmetry or RWL. Additionally, our results showed that leaf dry weight per unit area, which is usually associated with the photosynthetic capacity of plants, increases with an increasing A because the scaling exponent of leaf dry weight versus A is greater than unity. This suggests that a large leaf surface area requires more dry mass input to support the physical structure of the leaf.