The Influence of Rootstock on the Mineral Composition of Valencia Orange Leaves

Abstract

Rootstocks have been shown (7,8, 9,11,13) to exert an influence on tree growth, disease resistance, and fruit quality factors of various types of citrus. Recent work in California (5,6) in which the leaves of orange, grapefruit, and lemon trees on a large number of different rootstocks were analyzed for several nutritive elements, strongly suggests that the amounts of these minerals in the scion leaves may be affeeted by the rootstock used.Since one of the objectives of the nutritionial research program at this station is an attempt to associate the mineral composition of citrus leaves with tree performance, fruit quality, and fertilizer utilization, it is desirable to know as much as possible about the effect of rootstock on the mineral content of the leaves. Some information on eleven nutrient elements has been obtained with Valencia orange trees on six different rootstocks, under Florida conditions, and is presented herewith. Materials and methodsA rootstock test with Valencia orange was laid out in a randomized block arrangement in 1942 by other members of this station staff for the purpose of comparing the six rootstocks in respect to their effect on various aspects of tree growth, yield, and fruit quality. The rootstocks used were sour orange (Citrus Aurantiurm), Rough lemon (C. Linton), Rusk citrange (Poncirts trifoliata x C. sinensis), Bowen grapefruit (C. paradisi), Cleopatra mandarin (C. reticulata) and Parson Brown (sweet) orange (C. sinensis). The budded trees were two years old when the experiment started, and had been in the field five years when leaves were taken for analysis in late July, 1947. The soil is Lakeland fine sand located near Tavares, Florida. A complete mixed fertilizer (N, P, K, Mg, Mn, Zn, Cu, and B) was applied uniformly to all plots three times each year. During the first three years applications were made manually, while a mechanical distributor was used for the last two years. Dolomitic limestone was applied uniformly to the entire experimental area at intervals in amounts sufficient to maintain the acidity of the soil at about pH 5.5. No nutritional sprays were applied at any time.Thirty-six 6-months-old leaves from non-fruiting shoots of the spring flush were collected in a uniform manner from each plot of three trees, with nine replications for each rootstock. The leaves were throughly scrubbed in a neutral detergent solution (sodium lauryl sulphate), rinsed four times in distilled water, dried to constant weight at 500 C, ground to a fine powder in a semi-micro Wiley mill provided with a nickel-coated

Ionic Accumulation in Citrus as Influenced by Rootstock and Scion and Concentration of Salts and Boron in the Substrate

“…These results on boron accumulation for these two rootstocks are in agreement with observations by other workers (13,23,26). Likewise, the boron values for Valencia and grapefruit in the control plot are similar to those reported for this area by REUTHER et al (24).…”

“…The average magnesium content of leaves of both scions on sour orange was 0.35% of the dried leaves and that of the same scions on Cleopatra was 0.18%. These values for magnesium are similar to those reported for Texas by REUTHER et al (24) and the differences between rootstocks are similar to those reported by other workers (14,26). There appears to be no evidence of magnesium deficiency in these leaves; Shary Red on sour orange rootstock, which showed excessive bronzing, had more magnesium than other combinations showing less bronzing.…”

“…They found that the rootstock tended to control the quantity of boron accumulated in the scion. Other workers (13,23,26), who used other varieties of citrus as scion and rootstock, confirmed these results.…”

“…The findings of HAAS (14) and SMITH et al (26) indicate that the accumulation of ions in citrus is complicated by the fact that most commercially grown citrus trees are composed of two species or varieties of citrus: 1. a scion, or top, such as the Valencia orange, budded onto 2. a seedling rootstock, such as sour orange. These workers found highly significant differences in concentrations of nitrate, potassium, calcium, magnesium, manganese, copper, boron, zinc, and iron ions in the leaves of the scion that are attributable to a rootstock influence.…”

Mineral Composition of Chlorotic Orange Leaves and Some Observations on the Relation of Sample Preparation Technique to the Interpretation of Results

“…The drying, grinding (in a semi-micro Wiley mill equipped with a nickel-coated screen), storage, and analysis were all carried out as previously described (13,14 Results and discussion Iron was assumed to be a general surface contaminant and was used as an indicator of efficacy of washing in initial tests. Since nearly all citrus leaves have on them visible dust particles, no samples were analyzed without some washing treatment.…”