Nitrogen as a mitigator of salt stress in yellow passion fruit seedlingss

Abstract

The poor chemical quality of water, especially in arid and semiarid regions, almost always precludes the practice of irrigated agriculture, thus demanding the adoption of techniques that mitigate the deleterious effects of excess salt on soil and plants. The aim of this research was to evaluate the effectiveness of nitrogen fertilization in mitigating the negative effects of excess salt in irrigation water on the growth of yellow passion fruit seedlings grown in a greenhouse in plastic tubes containing 0.65 dm3 of substrate. The treatments were organized in randomized blocks, in accordance with a 5 × 3 factorial scheme – five electrical conductivities of irrigation water (0.3, 1.0, 2.0, 3.0, and 4.0 dS m?1) combined with three levels of nitrogen fertilizer (no nitrogen fertilization and 150 mg dm?3 of N derived from either ammonium sulfate or urea). Evaluations were performed 80 days after sowing and consisted of measuring the seedling height, stem diameter, number of leaves, leaf area, leaf nitrogen content, leaf concentration of chlorophyll a and b and total chlorophyll, specific leaf area, leaf area ratio, and Dickson quality index. An increase in the electrical conductivity of irrigation water hindered the production of yellow passion fruit seedlings. Nitrogen fertilization, with urea or ammonium sulfate, mitigated the effects of irrigation water salinity and favored the growth and quality of yellow passion fruit seedlings. Yellow passion fruit seedlings with a minimum quality standard (DQI) can be produced with irrigation water with salinity of 1.8 dS m?1, which means they can be considered as moderately sensitive. The higher quality provided by nitrogen to the yellow passion fruit seedlings made them more tolerant to salinity, allowing the use of water with salinity of 2.1 and 2.5 dS m?1 under fertilization with ammonium sulfate and urea, respectively.

Allometry and morphophysiology of papaya seedlings in a substrate with polymer under irrigation with saline water

“…The increase in salinity can also change the area and the photosynthetic apparatus (Taiz et al, 2017). In seedlings of papaya (Sá et al, 2013b) and yellow passion fruit (Bezerra et al, 2019), reductions were verified in the number of leaves and in the leaf area with the increase in water electrical conductivity, with more intense effects for the leaf area. Therefore, it is necessary to adequate the irrigation management in order to mitigate the effects of salt excess in the irrigation water since allometric or morphometric allocations are commonly-employed mechanisms by plants when exposed to water or salt stress conditions.…”

“…The leaf area ratio is an expressive parameter for the capture potential of photosynthetically active radiation, in which lower values imply greater photosynthetic efficiency (Fagundes et al, 2015). Leaf alterations were also observed, such as reductions in size and thickness, with the increase in the specific leaf area being the indirect result of the production of thinner leaves (Bezerra et al, 2019), resulting in the reduction of efficiency in the use of solar irradiance (Taiz et al, 2017), considering that higher values indicate lower concentrations of chloroplasts and enzymes related to photosynthesis (Evans & Pooter, 2001), even with greater mass allocation to the leaves in comparison with the remaining organs of the seedlings, such as observed in the leaf mass ratio.…”

“…The increase in the electrical conductivity also increased the specific leaf area and the leaf area ratio in yellow passion fruit seedlings (Bezerra et al, 2019), besides increasing this last index also in papaya seedlings (Santos et al, 2015). However, Sá et al (2013b), when evaluating papaya seedlings, observed a reduction in the leaf area ratio with the increase of the electrical conductivity of the irrigation water, although considering only the shoot dry mass in the calculation of this index, which may justify possible distinctions.…”

“…In papaya cultivation, salt excess damages seedling formation (Cavalcante et al, 2010;Sá et al, 2013a, b;Santos et al, 2015), yield, and quality of fruits, being then essential to use quality seedlings for the formation of an orchard (Bezerra et al, 2014). One index used to infer the quality of seedlings is the Dickson quality index (Dickson, 1960), based on the biometric relationships of the shoot and root parts, resulting from their physiological interactions reflected on plant architecture (Bezerra et al, 2019).…”

Shade nets and substrates in seedling production of Annona squamosa L. in the Roraima Cerrado

“…These results confirm those found for DQI, since no statistically significant differences were observed between environments (Table 5). DQI is widely used for the selection of high-quality seedlings because it integrates the morphological variables of plant height, diameter, and biomass into a weighed equation (BEZERRA et al, 2019). The higher the DQI, the more uniform the plant growth, which was observed in substrates S2 and S3.…”