Salinity is one of the major factors limiting avocado yield, primarily due to the high concentration of ions in irrigation water. An experiment was conducted on 2 year old avocado plants (Persea americana Mill.) cv. Hass, grafted onto Duke 7 clonal rootstock growing in pots, to determine the effect of salt stress on growth, as well as physiological and biochemical responses, and the effect of seaweed extract (Ascophyllum nodosum) on salinity stress. Treatments consisted of different types of irrigation water: distilled water, 9 mM NaCl water, distilled water + 2.25 mL of seaweed extract, 9 mM NaCl water + 2.25 mL of seaweed extract and, 9 mM NaCl water + 1.5 mL of seaweed extract. The irrigation treatment was applied every 15 days for 8 months. Treatments with salt reduced plant growth by approximately 50% of the fresh weight of all avocado plant tissues. Seaweed extract reduced the effects of abiotic stress only at an early stage, and increased potassium (K) and calcium (Ca) concentrations in leaves.

Both nitrogen and calcium fertilization management are vital for crops, where an imbalance of these elements can cause both physiological and yield problems. It has been proposed that nitrogen absorption, particularly ammonium, is in part dependent on calcium supply. Moreover, the balance between these two nutrients could be a key indicator of plant growth in some species. Tomato, one of the most cultivated crops worldwide, can also be widely affected by nutritional imbalance. Using large amounts of N fertilizers could lead to an imbalance with other nutrients and, thus, detrimental effects in terms of plant development and yield. Here we show that ammonium excess has a negative impact on plant development and results in calcium deficiency. Moreover, a deficit in calcium nutrition not only affects calcium concentration but also leads to a restriction in N uptake and reduced N concentration in the plant. These effects were evident at the seedling stage and also during flowering/fruit set. Using PCA analysis, we integrated both phenotypic and nutritional imbalances in seedlings and grown plants. Interestingly, the Ca/N ratio appears to be a key indicator to monitor appropriate N and calcium nutrition and more importantly the balance between both. Maintaining this balance could be an essential element for tomato crop production.

A two-year study was conducted to determine how soil texture affects calcium (Ca) absorption and partitioning in potted ‘Hass’ avocado trees. Trees were planted in 200 L pots in one of four soil types: clay (C), clay loam (CL), sandy loam (SL) or sand (S). Prior to planting, Ca content in each soil was in the normal range of availability, although the Ca concentration was highest in C soil. After two years of tree development, dry weights of shoots and roots were significantly higher in the SL and S soils than in C soil. Trees in the C soil had higher wood dry weight than trees in SL or S soils. The Ca contents (absolute quantities, not concentrations) in the roots, shoots and whole tree were significantly lower in the C soil than in the SL or S soils. The K/Ca ratio of trees in the C soil (K/Ca = 1.5) was significantly higher than that in the other soil types. Stem water potential was significantly lower for trees in the C soil compared to the other soils. These results indicate that Ca absorption and partitioning in young avocado trees varies with soil texture, probably associated with soil effects on root growth and/or plant water status.

Boron (B) is an essential element for plants. B availability depends on the physical and chemical characteristics of the soil and the quality of irrigation water. Under natural conditions, both toxic and deficit concentrations can occur and should be managed for crop production. However, the range between deficiency and toxicity is narrow. The objective of this study was to determine the response of cherry trees to deficient (0.04 mg kg⁻¹), adequate (1.1 mg kg⁻¹), and toxic (3.75 mg kg⁻¹) B concentrations in the soil by measuring growth, biomass, photosynthetic parameters, visual symptoms, and morphological changes. Plants treated with a toxic dose had more spurs and shorter internodes than those treated with adequate and deficient doses. The white root weight (50.5 g) at low B concentrations had the most roots compared with the adequate (33.0 g) and toxic (22.0 g) concentrations. The stem weight and biomass partitioning were higher for white roots and stems at B-deficient and -adequate doses than at toxic doses. The net photosynthesis (Pn) and transpiration rate (E) were significantly higher in plants with adequate concentrations of B. Stomatal conductance (Gs) was higher in B-deficient plants. Morphological and visual differences were observed between treatments. The results showed that it is essential to adequately manage B in cherry crops to avoid the adverse effects of both low and toxic concentrations.

Calcium (Ca) is often supplied to crop species to prevent the occurrence of Ca–related disorders. Mechanisms of Ca absorption and transport are not fully understood and the effectiveness of root and/or foliar Ca fertilization may be variable. To characterize the rate of Ca absorption and transport, trials were developed with chili pepper and sweet cherry plants, using 45CaCl2 as a tracer. The Ca treatments supplied were: (1) No 45Ca (control); (2) 45Ca soil application; (3) 45Ca supply to basal leaves, and (4) 45Ca application to apical leaves. After two months, plants were harvested for biomass and Ca content determination. The recovery of 45Ca in different plant parts was measured with a liquid scintillation counter and leaf traits were observed by scanning electronic microscopy. In general, the highest 45Ca concentrations were recovered in treated organs, while root applications led to highest 45Ca translocation rates, which varied between chili pepper and cherry plants. For chili pepper, 45Ca applied to the soil was detected mainly in roots (44 %) followed by leaves (36.6 %) stems (17.4 %) and fruits (2 %). In sweet cherry trees, soil–applied 45Ca was principally recovered in roots (45.3 %), shoots (28.5 %), leaves (14.3 %) and trunks (11.9 %). The results provide evidence of increased absorption of root–applied Ca, as well as different degrees of Ca mobility between species. Foliar application led to major Ca increases in treated leaves, with Ca transported to other plant organs after apical leaf Ca supply chiefly in cherry trees.