Influence of Alternate Bearing on Leaf and Fruit Mineral Composition at Different Developmental Stages of Date Palm Fruits

Abstract

‫اﻟﺒﺤﺚ.‬ ‫ھﺬا‬ ‫ﻣﺜﻞ‬ ‫أﺳﺘﻤﺮارﻳﺔ‬ ‫اﻟﻰ‬ ‫اﻟﺤﺎﺟﺔ‬ ‫ﻋﻠﻰ‬ ‫اﻟﻨﺘﺎﺋﺞ‬ABSTRACT: Samples of leaflets and fruits at different stages were collected from 6 "on-palms" and 6 "off-palms" (15-16 years) of the Fard Cultivar. Samples were dried, ashed and digested. Macro and micronutrient concentrations of K, Ca, Mg, Na, Fe, Zn, Cu and Mg were determined by ICP-AES and N was measured by Kjeldhal method. Significant changes in the elemental concentrations of leaf and fruit occurred between Kimri (green color) and Bisir (yellowish-red color) development Bisir (yellowish-red color) development Bisir stages. Potassium and Mg concentration was reduced in leaf and fruit. Calcium and Na were reduced in the fruit and increased in the leaf. Iron, Zn and Mn were not significantly different between Bisir and Bisir and Bisir Kimi. However, Fe in the fruit and leaf increased between Kimri and Bisir and decreased from Bisir and decreased from Bisir Bisir to Rutab stages. The concentration of Ca, Mg, Fe and Mn was higher in the leaf than fruit. In contrast K, Zn and Cu were higher in the fruit. Higher Ca and Mg in leaves through the developmental stages were associated with higher concentration of K in the fruit than the leaf. These variations in the leaf and fruit elemental concentration were associated with physiological and biochemical changes during fruit development. Significant differences in the fruit elemental concentrations between the "on" (high yield producing) and "off" (low yield producing) palms during the developmental stages were in Ca, K, Mn and Fe and in the leaf in Mg and K. However, the general trend during Rutab (honey color, soft tissue) indicates that "off-palm" leaves have higher N, Ca, Mg, Fe, Zn, Cu and Mn than "on-palm" leaves. Potassium and Na were higher in the "on-palm" leaves than "off-palm" leaves. But in the fruit, Rutab and Na were higher in the "on-palm" leaves than "off-palm" leaves. But in the fruit, Rutab and Na were higher in the "on-palm" leaves than "off-palm" leaves. But in the fruit Ca, Mg, Fe, and Zn content followed similar trends as in the "off-palm" leaves; in contrast to leaves, K and Na were higher in "off-palms" fruits and Cu and Mn higher in "on-palm" fruits. The results indicate the need for further research.

Heavy Metals and the Alternate Bearing Effect in the Date Palm (<i>Phoenix dactylifera</i>)

“…It is probable that an "on" palm could be determined as having a B Table 1. Summarising mean elemental concentrations (in mg/kg) in "on" and "off" fruit and leaflets for each development stage for most of the elements considered in this review [2] concentration in the leaflets of greater than 3.5 mg/kg during Bisir, whereas an "off" palm has less than this ( Table 1). This demonstrates that a lack of B could contribute to the poor growth seen in "off" palms [30].…”

“…Calcium is an essential element and helps maintain ionic balance in plants [27]. For the date palm, it has been found that significant differences in the Ca concentration exist between the "on" and "off" trees during one of the fruit developmental stages [2]. More specifically, the "off" palm leaflets had higher Ca levels than the "on" palm leaves during the Rutab stage [2] ( Table 1).…”

“…Alternate bearing in some date cultivars is of growing concern [2]. High yields are associated with low-quality fruits; in other words, small dates with high acidity and tannin, but low sugar content [3]- [6].…”

“…There will be competition between leaflets and fruit for nutrients and carbohydrates during this time. The fruit and leaf developmental stages would be expected to control movement of these substances [2] [19]- [22]. El Mardi et al [2] investigated the changes in mineral nutrients during fruit developmental stages in relation to alternate bearing in the Fard cultivar of the date palm.…”

“…It works on the principle of cold vapour atomic absorption at 253.7 nm. For the determination of N, the Kjeldahl method was exploited [2] [24]. Here, the sample is digested in boiling sulphuric acid and subjected to several further steps before finishing with an acid-base titration.…”