[Effects nutrients on the seedlings root hair development and root growth of Poncirus trifoliata under hydroponics condition].

Ahydroponics experiment was conducted to study the effects of nutrients (N, P, K, Ca, Mg, Fe, and Mn) deficiency on the length of primary root, the number of lateral roots, and the root hair density, length, and diameter on the primary root and lateral roots of Poncirus trifoliata seedlings. Under the deficiency of each test nutrient, root hair could generate, but was mainly concentrated on the root base and fewer on the root tip. The root hair density on lateral roots was significantly larger than that on primary root, but the root hair length was in adverse. The deficiency of each test nutrient had greater effects on the growth and development of root hairs, with the root hair density on primary root varied from 55.0 to 174.3 mm(-2). As compared with the control, Ca deficiency induced the significant increase of root hair density and length on primary root, P deficiency promoted the root hair density and length on the base and middle part of primary root and on the lateral roots significantly, Fe deficiency increased the root hair density but decreased the root hair length on the tip of primary root significantly, K deficiency significantly decreased the root hair density, length, and diameter on primary root and lateral roots, whereas Mg deficiency increased the root hair length of primary root significantly. In all treatments of nutrient deficiency, the primary root had the similar growth rate, but, with the exceptions of N and Mg deficiency, the lateral roots exhibited shedding and regeneration.

[Effects of growth regulators and growth media on root-hair development of Poncirus trifoliate].

By using river sand and mixed soil as growth media, and treating with different concentration IBA, ETH, and NAA, this paper studied the root-hair development of Poncirus trifoliate seedlings, and the development cycle and distribution pattern of the root-hairs under phosphorus deficiency in sand culture. The root-hairs had a development cycle of about 4 days, and formed block-shaped and clumped, mainly around root, and with uneven distribution. Sand culture gave rise to the production of more root hairs, with an average of 486.3 per tap root, and treating with 1.0 micromol x L(-1) of IBA and ETH notablypromoted root-hair development. The phosphorous deficiency in sand culture induced more roothair formation (636.3 per tap root). Mixed soil culture produced lesser root-hairs (212.3 per taproot), and all the test growth regulators had no obvious effects on the root-hair development.

[Effects of inoculation with arbuscular mycorrhizal fungi on AIPO4 uptake by Poncirus trifoliata].

With sand culture in greenhouse, this paper studied the effects of inoculation with arbuscular mycorrhizal (AM) fungi Glomus mosseae and G. versiforme on the utilization of insoluble phosphate AlPO4 (Al-P) by trifoliate orange (Poncirus trifoliata) seedlings. The results indicated that inoculation with AM fungi notably increased the dry matter, P content, and P absorption rate of P. trifoliata. The contribution of mycorrhiza, P uptake by plant and AM fungi, and the contribution of AM fungi in P uptake by P. trifoliata increased greatly with increasing Al-P level in the medium. Inoculation with AM fungi greatly increased the excretion of phosphatase, especially acid- and neutral phosphatase, from plant root and hyphae, but the excretion amount decreased with increasing Al-P level. The contribution of the fungi in P uptake by P. trifoliata was significantly positively correlated with the amounts of acid-, neutral-, alkaline-, and total phosphatase.

[Effects of arbuscular mycorrhizal fungi on reactive oxygen metabolism of Citrus tangerine leaves under water stress].

In a pot experiment, this paper studied the effects of arbuscular mycorrhizal (AM) fungus Glomus versiforme (Karsten) Berch inoculation on the reactive oxygen metabolism of Citrus tangerine Hort. ex Tanaka leaves under water stress. The results showed that water stress decreased the colonization of G. versiforme on C. tangerine roots significantly, with a decrement of 33%. Under normal water supply and water stress, G. versiforme inoculation increased the leaf P content by 45% and 27%, and decreased the leaf malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents by 25% and 21%, and 16% and 16%, respectively, compared with the control. Inoculation with G. versiforme enhanced the activities of leaf superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), and increased the contents of leaf soluble protein, ascorbate (ASC) and total ascorbate (TASC) notably, regardless soil moisture condition. Under water stress, G. versiforme inoculation decreased the leaf superoxide anion radical (O2-*) content by 31%, compared with that under normal water supply. It was suggested that the drought resistance of C. tangerine leaves was enhanced after G. versiforme inoculation.

[Effects of exogenous ABA and GA3 on sugar concentration in flesh of cara cara navel orange].

The concentration of glucose, fructose, sucrose and total sugar were determined after exogenous ABA and GA3 treatment during young period of fruit and before fruit coloring in flesh of Cara Cara Navel Orange. The results showed that 10 mg x L(-1) ABA treatment improved glucose, fructose and total sugar concentration significantly or very significantly, 50 mg x L(-1) ABA treatment improved sucrose concentration very significantly, but 100 mg x L(-1) ABA treatment reduced glucose concentration very significantly. GA3 treatment of lower and middle concentrations (10, 50 and 250 mg x L(-1)) improved sucrose concentration very significantly, 10 mg x L(-1) GA3 treatment had no remarkable effect on glucose and fructose concentration but improved total sugar concentration very significantly, GA3 treatment of 50, 250 and 500 mg x L(-1) decreased glucose, fructose and total sugar concentration very significantly. Therefore, ABA treatment of lower concentration could improve one or several kinds of sugar concentration, but GA3 treatment of higher concentration (250 and 500 mg x L(-1)) prohibited sugar accumulation in flesh of Cara Cara Navel Orange seriously.

Reactive oxygen metabolism in mycorrhizal and non-mycorrhizal citrus (Poncirus trifoliata) seedlings subjected to water stress.

The effect of the arbuscular mycorrhizal (AM) fungus, Glomus versiforme, on growth and reactive oxygen metabolism of trifoliate orange (Poncirus trifoliata) seedlings was studied in potted plants under well-watered (WW) and water stressed (WS) conditions. Water stress significantly decreased root colonization. Shoot dry weight, plant height and stem diameter were higher in AM than in non-AM seedlings regardless of the water status. Inoculation with G. versiforme increased root dry weight and leaf number per plant of WW seedlings. There was less malondialdehyde (MDA) concentration in leaves and roots of AM seedlings, as well as lower hydrogen peroxide (H(2)O(2)) and superoxide anion radical (O(2)(-)) concentrations in AM roots under WW and WS conditions. AM inoculation did not affect the H(2)O(2) and O(2)(-) concentrations of WW leaves. Whether WS or not, AM symbiosis notably increased the guaiacol peroxidase (G-POD) activity of leaves, glutathione reductase (GR) activity of leaves and ascorbate peroxidase (APX) activity of roots. AM infection also markedly increased the APX activity of WS leaves. Soluble proteins and glutathione (GSH) in leaves and roots and ascorbate (ASC) in leaves were higher in WW AM than in WW non-AM seedlings. AM infection also enhanced the ASC and GSH contents of leaves and roots in WS seedlings. Cross-tolerance might occur in AM plants and be enhanced by AM symbiosis. Our results suggest that the increased concentrations of antioxidant enzymes and non-enzymatic antioxidants found in AM plants may serve to protect the organism against oxidative damage, enhancing drought tolerance.

Arbuscular mycorrhizal fungi influence growth, osmotic adjustment and photosynthesis of citrus under well-watered and water stress conditions.

The influence of arbuscular mycorrhizal (AM) fungus Glomus versiforme on plant growth, osmotic adjustment and photosynthesis of tangerine (Citrus tangerine) were studied in potted culture under well-watered and water stress conditions. Seven-day-old seedlings of tangerine were transferred to pots containing Glomus versiforme or non-AMF. After 97 days, half of the seedlings were subject to water stress and the rest were well-watered for 80 days. AM colonization significantly stimulated plant growth and biomass regardless of water status. The soluble sugar of leaves and roots, the soluble starch of leaves, the total non-structural carbohydrates (NSC) of leaves and roots, and the Mg(2+) of leaves were higher in AM seedlings than those in corresponding non-AM seedlings. The levels of K(+) and Ca(2+) in leaves and roots were higher in AM seedlings than those in non-AM seedlings, but differences were only significant under water stress conditions. Moreover, AM colonization increased the distributed proportions of soluble sugar and NSC to roots. However, the proline was lower in AM seedlings compared with that in non-AM seedlings. AM seedlings had higher leaf water potential (Psi), transpiration rates (E), photosynthetic rates (Pn), stomatal conductance (g(s)), relative water content (RWC), and lower leaf temperature (Lt) than corresponding non-AM seedlings. This research also suggested that AM colonization improved the osmotic adjustment originating not from proline but from NSC, K(+), Ca(2+) and Mg(2+), resulting in the enhancement of drought tolerance.

[Effects of arbuscular mycorrhizal fungi on plant growth and osmotic adjustment matter content of trifoliate orange seedling under water stress].

The effects of arbuscular mycorrhizal fungi Glomus mosseae on plant growth and osmotic adjustment matter content of trifoliate orange [Poncirus trifoliata (L.) Raf.] seedlings under water stress were studied in potted culture. The results showed that arbuscular mycorrhizal fungi inoculation could increase plant growth, such as plant height, stem diameter, leaf area, shoot dry weight, root dry weight and plant dry weight, when the water content of soil was 20%, 16% and 12%. Arbuscular mycorrhizal fungi inoculation also promoted active absorbing areas of plant root and absorption of P from plant rhizosphere, enhanced the accumulated quantities of soluble sugar content in leaves and roots, and reduced proline content of leaf. Plant inoculated with arbuscular mycorrhiza had higher plant water use efficiency than non-mycorrhizal plants. Drought tolerance of trifoliate orange seedling inoculated with arbuscular mycorrhiza was enhanced. Effects of arbuscular mycorrhizal fungi inoculation on trifoliate orange seedling under 20% and 16% water content of soil were more significant than under 12% water content of soil. Arbuscular mycorrhizal fungi infection was severely restrained by 12% water content of soil. Thus, effects of arbuscular mycorrhizal fungi on plant probably positively related to the arbuscular mycorrhizal inoculated percentage.