Plant Nutrition
Farnaz Kargar; Abbas Mirsoleimani; Mahdi Najafi-Ghiri
Abstract
Purpose: Nitrogen (N) plays a crucial role in citrus growth, but its deficiency or excess can disrupt nutrient balance and physiological functions in plant. This study investigated how varying N levels (2, 4, 8, 16, and 32 mM) affect growth, photosynthesis, root morphology and nutrient interactions in ...
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Purpose: Nitrogen (N) plays a crucial role in citrus growth, but its deficiency or excess can disrupt nutrient balance and physiological functions in plant. This study investigated how varying N levels (2, 4, 8, 16, and 32 mM) affect growth, photosynthesis, root morphology and nutrient interactions in sour orange (Citrus aurantium L.) seedlings. Research Method: Seedlings were grown in nutrient solutions with different N concentrations. Biomass, photosynthetic efficiency (Fv/Fm, PI), chlorophyll content, nutrient uptake, and nitrate reductase activity were analyzed. Findings: Maximum and significant plant dry weight (4.95 g), root length (51.5 cm), chlorophyll content (8.6 mg g⁻¹ FW), and photosynthetic efficiency (Fv/Fm = 0.73; PI = 4.2) occurred at 16 mM N compared to 2 mM N. In contrast, N deficiency (2–8 mM) reduced growth and photosynthetic performance, while N toxicity (32 mM) decreased plant biomass by 50%, impaired chlorophyll synthesis, and disrupted photosystem II efficiency (Fv/Fm = 0.55). Excessive N (32 mM) altered nutrient homeostasis, increasing root Ca and K concentration by 0.82% and 2.49% respectively but reducing their translocation to shoots, elevating the Ca/K ratio a key indicator of K deficiency risk in calcareous soils. Nitrate reductase activity declined under toxicity, reflecting suppressed N assimilation. Root N/Ca ratio decreased with increasing in N concentration and Ca/K ratio of root in N16 and N32 treatments was higher than that in other N treatments. Phenolic compounds accumulated in roots under high N, suggesting oxidative stress mitigation. Research limitations: No limitations were found. Originality/Value: Excessive N disrupts nutrient balance, photosynthetic inhibition, and growth suppression while 16 mM N optimizes sour orange growth.
Plant Stress
Simeneh Tamrat Alemu; Habtamu Gebre
Abstract
Purpose: Ultraviolet-B radiation was inducing enormous stress at highland and coldest area since it increases more than 40% at highland when we compare with lowland. Therefore, this review aims to assess and depict impacts of Ultraviolet-B radiation on photosynthetic efficiency, growth performance, and ...
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Purpose: Ultraviolet-B radiation was inducing enormous stress at highland and coldest area since it increases more than 40% at highland when we compare with lowland. Therefore, this review aims to assess and depict impacts of Ultraviolet-B radiation on photosynthetic efficiency, growth performance, and yield of crops based on altitude. Findings: Indicate that ultraviolet-b radiation has a severe effect on photosynthesis, especially the coldest time. It reduces photosynthetic efficiency in such an area, but it depends on the type of the crop and cultivar difference. On the other hand, it reduces growth performance and biomass accumulation based on altitude. There is a contrasting view on a net-assimilation rate on different studies condition. The effect of UV-B on crop yield was more contrasting in some studies says no effect on other studies it says it affect, but this contradictory result was mainly due to the difference in study conditions, still current studies on Yield revealed that UV-B has a high impact on yield. Research limitations: Ultraviolet-B radiation has high effect on the highland area, but there is no much research focuses, but UV-B was profoundly affecting photosynthetic efficiency, growth performance and yield of crops on highland area. Directions for future research: UV-B was reducing crop production, and productivity at highland and this review gives more insights on UV-B impact at the highland and allow UV-B adaptive and preventive investigation in the future.
