Chrysovalantou Antonopoulou

The influence of radiation quality on the in vitro rooting and nutrient concentrations of peach rootstock

The effect of radiation quality (350 – 740 nm) and darkness (D) on in vitro rooting, and chemical composition of the peach rootstock GF 677 was studied. Shoot explants were exposed for four weeks to cool white (control) (W), red (R), blue (B), green (G) or yellow (Y) radiation from fluorescent tubes. Some of the explants were kept in D during the rooting stage and others were maintained only for the first 2- or 4-d under R, B, G, Y or D, and subsequently were transferred to W. W was the most effective radiation source for adventitious root formation of GF 677 explants. Rooting was inhibited in those plants that remained in continuous D, and R reduced root growth in all treatments. The 2- or 4-d exposure to D, Y or B followed by W helped adventitious root development similarly as did W. G significantly increased Fe concentration in roots.

Effects of High Boron Concentration and Scion-Rootstock Combination on Growth and Nutritional Status of Olive Plants

ABSTRACT Own rooted olive plants (Olea europaea L.) of the cvs. ‘Megaritiki’ (M), ‘Chondrolia Chalkidikis’ (C), ‘Amfissis’ (A), ‘Kalamon’, ‘Koroneiki’, ‘Agiou Orous’, and wild olives, as well as the scion x rootstock combinations CxC, MxC, MxM, AxM, CxM, AxA, and CxA were irrigated with a nutrient solution containing 10 mg boron (B)/L for two months. In all the own rooted plants and in the rootstock—scion combinations of the same cultivar stem growth rate was decreased due to high B. The lowest B concentration in leaves and roots was found in ‘Kalamon’ and wild olives, respectively. ‘Megaritiki’ had higher leaf B concentration when grafted on ‘Megaritiki’ or ‘Chondrolia Chalkidikis’ compared to own rooted plants. The same cultivar as own rooted plant had higher root B concentration than as rootstock of the other tested cultivars.

Photosystem 2 activity of Citrus volkameriana (L.) leaves as affected by Mn nutrition and irradiance

Citrus volkameriana (L.) plants were grown for 43 d in nutrient solutions containing 0, 2, 14, 98, or 686 µM Mn (Mn0, Mn2, Mn14, Mn98, and Mn686, respectively). To adequately investigate the combined effects of Mn nutrition and irradiance on photosystem 2 (PS2) activity, irradiance response curves for electron transport rate (ETR), nonphotochemical quenching (qN), photochemical quenching (qP), and real photochemical efficiency of PS2 (ΦPS2) were recorded under 10 different irradiances (66, 96, 136, 226, 336, 536, 811, 1 211, 1 911, and 3 111 µmol m−2 s−1, I66 to I3111, respectively) generated with the PAM-2000 fluorometer. Leaf chlorophyll content was significantly lower under Mn excess (Mn686) compared to Mn0; its highest values were recorded in the treatments Mn2-Mn98. However, ETR and ΦPS2 values were significantly lower under Mn0 compared to the other Mn treatments, when plants were exposed to irradiances ≥96 µmol m−2 s−1. Furthermore, Mn0 plants had significantly higher values of qN and lower values of qP at irradiances ≤226 and ≥336 µmol m−2 s−1, respectively, than those grown under Mn2-Mn686. Irrespective of Mn treatment, the values of ΦPS2 and qN decreased, while those of qP increased progressively by increasing irradiance from I136 to I3111. Finally, Mn2-Mn98 plants were less sensitive to photoinhibition of photosynthesis (≥811 µmol m−2 s−1) than the Mn686 (≥536 µmol m−2 s−1) and Mn0 (≥336 µmol m−2 s−1) ones.

Effect of nitrogen source on olives growing in soils with high boron content

A greenhouse experiment was conducted to study the effects of nitrogen (N) forms (NO3–, 2.6 mmol/L; NH4+, 2.6 mmol/L; NO3–, 1.0 mmol/L plus NH4+, 1.6 mmol/L) and boron (B) (0.025, 0.5 and 1.0 mmol/L) on the growth and mineral composition of olive plants (Olea europaea L.). One-year-old own-rooted plants of the olive cultivars Megaritiki, Chondrolia Chalkidikis, Koroneiki and Kalamon were grown in plastic bags containing inert sand–perlite medium (1 : 1) and were irrigated with a 50% modified Hoagland nutrient solution. The plants treated with NO3– and 1.0 mmol B/L presented higher leaf B than those treated with NH4+ and 1.0 mmol B/L, for all cultivars. The addition of ammonium form fertilisation caused a significant accumulation of B to root tissues when the latter consisted of 0.5 mmol/L. As B was increased in the NO3–-N treatments, the number of leaves and the root dry weight of cv. Megaritiki as well as the plant height of cvv. Koroneiki and Kalamon were reduced. The above results suggest that in olive, addition of NH4+ to high B soils may be more beneficial for growth of olives than addition of NO3–. In most cases N form did not affect total leaf and root N levels. Also, the NH4+-N treatments showed a decline in root phosphorus (P) and an increase in leaf potassium with increased B. The general trend was a decrease of P in leaves with increasing B.

Responses of trifoliate orange (Poncirus trifoliata (L.) Raf.) to continuously and gradually increasing NaCl concentration

Abstract The effect of continuous or gradual stress due to NaCl on in vitro growth, proline and sugar accumulation and nutrient acquisition of trifoliate orange (Poncirus trifoliata (L.) Raf.) explants was studied. Apical shoot tips obtained from previous subculture were transferred to a Murashige and Skoog nutrient medium for proliferation and were exposed to continuous or gradual salinity stress for 42 days. The salt used to induce salinity was NaCl added in six concentrations: 0, 50, 100, 150, 200 and 300 mM. Gradual salinization was achieved by transferring the explants sequentially every week to the above mentioned NaCl concentrations. Most salt treatments had a negative effect on the growth parameters of explants. Sodium concentration of explants increased in all NaCl treatments compared to control and it was higher in the treatments with gradual exposure to salinity. Potassium concentration was reduced, mostly in the treatments with continuous exposure. Calcium andMg concentrations increased in all saline treatments. In general, the high salinity level in the substrate enhanced the proline and sugar concentrations of the studied explants. In conclusion, salinity had significant impacts on the growth and chemical status of P. trifoliata.

Effects of NAA and vitamin B2 on in vitro rooting of Citrus

Abstract The effects of riboflavin combined with α-naphthaleneacetic acid on the in vitro rooting of sour and trifoliate orange explants were studied. After four weeks in culture, there was a reduction in both the rooting percentage and root length of sour orange explants. When riboflavin was added to the nutrient medium containing 0.1 mg dm−3 α-naphthaleneacetic acid, the rooting percentage of sour orange explants was reduced. However, in the treatments containing 1.0 mg dm−3 α-naphthaleneacetic acid the root length increased. Rooting in trifoliate orange explants was not distinctly affected by riboflavin. Increasing riboflavin concentration in the nutrient medium leads to a) the rooting percentage was affected (reduced) only in sour orange explants treated with 0.1 mg dm−3 NAA; b) the root length either decreased (0.1 mg dm−3 NAA) or increased (1.0 mg dm−3 NAA); and c) the root number was reduced in most treatments. Finally, it is strongly recommended that riboflavin in vitro should be extensively studied, as it has immense economic significance for commercial laboratories when it is added to the nutrient medium with the aim to reduce exogenous auxin levels, rather than transferring cultures to a growth-regulator-free medium.