Effect of Three Boron Concentrations in Soil on Growth and Physiology in Sweet Cherry Trees.

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.

Absorption and distribution of root, fruit, and foliar-applied 45 Ca in 'Clemenules' mandarin trees.

BACKGROUND: The mechanisms of calcium (Ca) absorption and transport in plants are still poorly understood. This study focused on assessing the absorption and distribution of Ca in different plant organs after root (soil), foliar, or fruit application to 6-year-old 'Clemenules' mandarin trees, grown in pots, using 45 Ca as a tracer. RESULTS: The rate of 45 Ca absorption and transportation in plant tissues varied according to the treatment method. The fruit and shoot Ca supply led to a rate of 97% to 98% 45 Ca retention in such organs. In Ca-treated fruits, 22% of the applied 45 Ca moved to the pulp and 78% remained in the flavedo and albedo. The fruit peel was examined by scanning electron microscopy and transmission electron microscopy (SEM and TEM) and variations were observed during fruit development. Following 45 Ca soil treatment, approximately 56% of 45 Ca activity was measured in the soil, with 19.5% determined in the roots, 14.6% in the trunks (90% in bark and sapwood and only 10% in heartwood), 9.6% in shoots, and 0.3% in fruits. CONCLUSION: Calcium mobility in 'Clemenules' mandarin trees is limited and depends on the mode of Ca fertilizer application. The distribution of Ca to and within the fruits may be limited during development because of structural and functional constraints. © 2020 Society of Chemical Industry.

Changes in fine-root production, phenology and spatial distribution in response to N application in irrigated sweet cherry trees.

Factors regulating fine-root growth are poorly understood, particularly in fruit tree species. In this context, the effects of N addition on the temporal and spatial distribution of fine-root growth and on the fine-root turnover were assessed in irrigated sweet cherry trees. The influence of other exogenous and endogenous factors was also examined. The rhizotron technique was used to measure the length-based fine-root growth in trees fertilized at two N rates (0 and 60 kg ha(-1)), and the above-ground growth, leaf net assimilation, and air and soil variables were simultaneously monitored. N fertilization exerted a basal effect throughout the season, changing the magnitude, temporal patterns and spatial distribution of fine-root production and mortality. Specifically, N addition enhanced the total fine-root production by increasing rates and extending the production period. On average, N-fertilized trees had a length-based production that was 110-180% higher than in control trees, depending on growing season. Mortality was proportional to production, but turnover rates were inconsistently affected. Root production and mortality was homogeneously distributed in the soil profile of N-fertilized trees while control trees had 70-80% of the total fine-root production and mortality concentrated below 50 cm depth. Root mortality rates were associated with soil temperature and water content. In contrast, root production rates were primarily under endogenous control, specifically through source-sink relationships, which in turn were affected by N supply through changes in leaf photosynthetic level. Therefore, exogenous and endogenous factors interacted to control the fine-root dynamics of irrigated sweet cherry trees.