Study On The Rules Of Calcium And Boron Nutrients Uptake During Citrus Fruit Development

Calcium(Ca) and Boron(B) are closely related to fruit development, and they are been thought to be key mineral elements which could affect fruit quality both directly and indirectly. Change rules of Ca and B concentrations in fruit were related to mechanisms of Ca and B uptake by fruit, which were the bases of nutrients applications. In the present work, the rules of Ca nutrient uptake by fruit of different type citrus cultivars and dynamics of B concentrations in Newhall (Citrus sinensis Osbeck) navel orange which presented symptom of B deficiency were studied, with the aim of finding the mechanisms of Ca and B uptake by fruit, and the causes of B deficiency in Newhall navel orange. 1. Study on the rules of Ca nutrient uptake during citrus fruit developmentThere are parthenocarpy and self-pollinated type varieties in citrus, and their growth and development are different. Change rules in concentrations of Ca and physiological substances (hormones and Ca~2+-ATPase etc.) in fruit throughout fruit development of parthenocarpic satsuma mandarin (Guoqing 1 and Kamei ) and self-pollinated tangerine (Huanong Bendizao and Egan 1) were comparatively investigated, with the aim of finding the rules of Ca nutrient uptake during citrus fruit development.1.1 Influence of fertilization on Ca uptake by fruit Changes in concentrations of Ca, B, potassium(K), IAA and GA1/3 in the ovary(fruitlet) were investigated around flowering of citrus i.e. parthenocarpic Guoqing l(Citrus unshiu Marc.) and self-pollinated Huanong Bendizao(C. reticulata Blanco). The results were as follows: (1) Ca and B concentrations in the ovary(fruitlet) of Guoqing 1 were at high levels before and at full bloom, and then decreased, but its K concentrations were correspondingly low before and at full bloom, thereafter increased. Ca and B concentrations were relatively low in the ovary of Huanong Bendizao before flowering, and increased after flowering, while its K concentrations were comparatively high before and at full bloom, and then declined. (2) Ca, B and IAA concentrations in the ovary(fruitlet) of the two cultivars were significantly positively correlated, but dynamics of Ca and B were not correlated to GA1/3. Above results showed that IAA concentration in the seedy fruit was increased by stimulus derived from fertilization, meanwhile, increased uptake of Ca and B into fruit, while IAA of parthenocarpic fruit was at high level before flowering, which kept Ca and B nutrients concentrations at high levels before flowering, but there was no direct relationship between K uptake by fruit and fertilization.1.2 Dynamics of different Ca forms, pectin concentrations and activity of Ca~2+-ATPase Changes of different Ca forms, pectin concentrations and Ca~2+-ATPaseactivities were investigated in the ovary(fruitlet), rind and pulp of fruit from parthenocarpic Kamei(Citrus unshiu Marc.) and self-pollinated Egan 1(C. reticulata Blanco) throughout fruit development. The results were as follows: (1) Dynamics of soluble Ca~2+ and Ca oxalate concentrations between the two cultivars were reverse, soluble Ca~2+ and Ca oxalate concentrations decreased in the ovary(fruitlet) of Kamei after flowering, whereas those of Egan 1 presented significantly increasing trends. Similarly decreasing trends of Ca pectate concentrations were observed in the ovary (fruitlet) from the two cultivars, Ca~2+-ATPase activity in the ovary of Kamei was relatively high before and at full bloom, and declined after flowering, while that of Egan 1 was relatively low before flowering and began to increase at full bloom. (2) During fruit enlargement, significant increases were presented in concentrations of soluble Ca~2+, Ca pectate and activities of Ca~2+-ATPase in both rind and pulp of the two cultivars, although their change dynamics were not accordant. Ca oxalate concentrations in the rind of both cultivars were relatively high, whereas remarkably decreasing trends were found for Ca oxalate in the pulp. Water soluble pectin concentrations of both rind and pulp from the two cultivars were markedly rising, and proto-pectin concentrations were relatively high during fruit enlargement, and then presented obviously declining trends during the late stage of fruit enlargement. Above mentioned results showed that rules of Ca uptake by ovary(fruitlet) and changes in concentrations of different Ca forms in the structural parts of fruit during fruit development were related to changes in activities of Ca~2+-ATPase and conversion between different Ca and pectin forms.1.3 Change rules in concentrations of Ca and other mineral elements Annual changes in concentrations of Ca and other mineral elements were investigated in whole fruit and the structural parts of fruit from parthenocarpic Kamei and self-pollinated Egan 1 throughout fruit development. Results were as follows: (1) Ca and B concentrations in the ovary (fruitlet) of Kamei were at high levels before and at full bloom, and then decreased, whereas those of Egan 1 were in the reversed trends, being at low levels before and at full bloom, and significantly higher after flowering. The trends of K and Mg between the two cultivars were similar and progressively decreased after flowering. (2) At the early stage of fruit enlargement, Ca concentrations in whole fruit from the two cultivars reached the maximum values, thereafter declined. Ca in the rind increased during fruit enlargement, but that of pulp decreased. Contrary to decreases in K and Mg concentrations in whole fruit and rind from the two cultivars during fruit development, both K and B in the pulp showed markedly increasing trends during fruit enlargement,especially B concentration increased more obviously in the pulp. Above mentioned results indicated that change rules of Ca concentrations clearly differed from those of other mineral elements in fruit throughout fruit development, and dynamics of Ca concentrations in the ovary(fruitlet) were significantly different between the two different type citrus cultivars arround flowering.1.4 Change rules of endogenous hormones during fruit development Changes in concentrations of IAA, ZR and GA3 in different fruit positions of Kamei and Egan 1 fruits were investigated during fruit development. The results showed that IAA concentrations in the rind of the two cultivars demonstrated similar trends with obvious peaks at the stage of fruit enlargement, though Egan 1 had the higher value. Opposite change patterns were observed in ZR concentrations between the two cultivars during fruit enlargement, when ZR concentration in Kamei rind was relatively high and increased progressively, whereas that of Egan 1 declined. GA3 concentrations of both cultivars presented similar change trend, increasing during fruit enlargement and then decreasmg. IAA, ZR and GA3 concentrations in Kamei pulp, were relatively high during eiriy fruit development, and thereafter were reduced conspicuously and remained at low levels. In Egan 1, IAA and GA3 concentrations were clearly increased during fruit enlargement, which were significantly higher than those of Kamei. ZR concentration in the pulp of Egan 1 decreased, with a trend similar to Kamei, but the former was lower than the latter. IAA, ZR and GA3 concentrations in the seed of Egan 1 were relatively high at 72 days after full bloom, followed by abrupt decrease to low but constant levels. Above observations indicated that there existed clear differences in dynamics of IAA, ZR and GA3 concentrations in fruits between the two cultivars, while the peaks of growth promoting hormones in the rind of both cultivars were presented in accordance with soluble Ca2+ of them.during fruit enlargement.1.5 Measures of Ca applications and their influences Ca concentrations of whole fruit, rind and pulp at the different development stages of Kamei satsuma mandarin fruit, which sprayed with spray treatments such as calcium nitrate(Ca(NO3)2), IAA, and IAA+Ca(NO3)2 at the stages of full bloom, 1 week and 3 weeks after full bloom, and 2 weeks before usual harvest were investigated, and their fruit main quality was analyzed in comparison with fruits infiltrated with Ca(NC>3)2 after usual harvest and fruits of tree storage(full ripe harvest). The results showed as follows: (1) Ca concentrations in the rind of all spray treatments increased more or less at 51 DAFB(at fruitlet period) and 112DAFB(during fruit enlargement), whereas Ca concentrations in whole fruit were notsignificantly different among sprays and control. At usual harvest, Ca concentrations in whole fruit and pulp of all sprays were significantly higher than those of control. (2) Soluble solids content(SSC) and titratable acidity(TA) of spray treatments were all statistically lower than those of control, while soluble sugar(SS) concentration, mean fruit weight, rind color parameters and relative inductivity of sprays did not differ significantly among sprays and control, SS/TA of all spray treatments were significantly higher than that of control. (3) At 30 days after usual harvest, Vc of IAA+Ca(NO3)2 spray and posharvest Ca infiltration treatments, and SSC and SS of tree storage fruit were all significantly higher than those of control and other treatments. 2. Study on the rules of B nutrient uptake during citrus fruit developmentIn the south of Jiangxi province of China, Newhall (Citrus sinensis Osbeck) navel orange presented severe symptom of B deficiency in leaves, whereas B deficiency symptom didn't obviously manifested on Skagg's Bonanza(C sinensis Osbeck) and other navel orange cultivars. In this study, Skagg's Bonanza n?vel orange was taken as the control, annual changes in concentrations of mineral elements including B and soluble sugar were investigated in fruit and leaves of Newhall navel orange.2.1 Relationship between B deficiency and annual changes in concentrations of B and soluble sugar in fruit and leaves of Newhall navel orange(1) Dynamics of B concentrations in fruit Two peaks of B concentrations were observed in the rind of the two cultivars during fruitlet growth and the stage of fruit enlargement, respectively. B concentrations in the rind were relatively high during fruitlet growth, and then those of both rind and pulp decreased, while the significant increases of B concentrations were detected in both rind and pulp from the two cultivars during the middle and late stage of fruit enlargement. (2) Dynamics of b concentrations in leaves B concentration in old leaves from last year of Newhall progressively decreased and remained relatively low level when those of both rind and pulp increased markedly during middle and late fruit enlargement, whereas B concentration in old leaves of Skagg's Bonanza was relatively high and its change range was relatively small. (3) Relationship between B and sugar During the middle and late stage of fruit enlargement, soluble sugar(SS) concentrations in both rind and pulp from the two cultivars accumulated significantly in accordance with B of them, but SS in the pulp of Newhall were lower than those of Skagg's Bonanza during the late period. Notable decreases and low values were presented for SS both in old leaves of the two cultivars and in spring-flush leaves of Skagg's Bonanza when SS sharply increased in fruit, whereas no obvious decrease wasfound for SS in spring-flush leaves of Newhall.12 Relationship between B deficiency and annual changes in concentrations of mineral elements besides B in fruit and leaves of Newhall navel orange(1) Ca and K During early fruit enlargement, significant increases were observed for Ca in the rind from the two cultivars, whereas B decreased, and change trends of Ca concentrations both in old leaves and in spring-flush leaves were reverse to those of B, respectively. K concentrations of old leaves from Newhall remained relatively constant and were higher than those of Skagg's Bonanza, and they were negatively correlated to Ca in old leaves, meanwhile, they obviously differed from dynamics of B concentrations in old leaves. During the early period(from 20 DAFB to SO DAFB),dynamics of K and B concentrations in spring-flush leaves were inverse. (2) Mg There was no obvious relationship between dynamics of Mg and changes of B concentrations in both fruit and leaves from the two cultivars, whereas, during middle and late fruit development(from 100 DAFB to 200 DAFB),dynamics of Mg concentrations were similar to B in spring-flush leaves of both. Mg concentrations of both old leaves from two cultivars and spring-flush leaves of Newhall were below the threshold limit for sufficiency during middle and late fruit development, furthermore, Mg in old leaves of Newhall was much lower. (3 ) Mn, Zn and Fe During the early period(from 20 DAFB to 60 DAFB) and the late stage(from 140DAFB to 200DAFB),change trends of Mn, Zn and Fe concentrations were reverse to that of B in old leaves from the two navel orange trees, respectively. Mn, Zn and Fe concentrations in spring-flush leaves and Mn and Fe concentrations in old leaves from Newhall were relatively lacking during the middle and late stage of fruit development, meanwhile, the symptom of B deficiency was clearly presented.