The small leaved white cross berry (Grewia tenax [Forssk.] Fiori) is a fruit-producing deciduous shrub or small tree of widespread occurrence in semi-arid and sub-humid tropical climates. Despite its well-recognized potential and high prices on local markets, there are no commercial plantations in Sudan. Wild plants have continuously been used to meet the growing commercial demand for their fruits. Recently, there has been an increased interest in finding alternative, potentially high-value cash crops to improve the income of small farmers who are currently depending upon growing and selling millet (Pennisetum glaucum [L.] R. Br.), sorghum (Sorghum bicolor [L.] Moench), sesame (Sesamum indicum L.), and groundnut (Arachis hypogaea L.). G. tenax has often been cited as a prime candidate for domestication as a useful horticultural plant. One major factor hampering this development is the limited and scattered knowledge available on this species. The purpose of this paper is to highlight the importance of G. tenax by providing information on its botanical and horticultural characteristics in the effort to promote its domestication and commercialization for regional and global markets.

To study the salt tolerance of baobab ( digitata L.) and tamarind (Tamarindus indica L.), the effect of salinity on growth and mineral uptake of seedlings was investigated. Four week old A. digitata and T. indica seedlings were grown in sand culture and irrigated with 0, 20, 40, 60 and 80 mM NaCl for a period of 20 weeks. In all salt treatments, A. digitata leaves showed severe injury symptoms (necrosis) and in the 20 mM treatment, a reduction of 66% dry weight occurred in comparison to the control plants. T. indica seedlings responded less strongly to salinity and leaf chlorosis appeared only in the 60 and 80 mM treatment. The reduction of dry weight in the 20 and 40 mM was less than 50%. Both species accumulated a high amount of Na + and Cl - in the leaf tissue compared to other fruit species. Our results indicate that in the seedling stage the tamarind is much more tolerant to NaCl salinity compared to the baobab.

Application of foliar iron (Fe) sprays is a common means of correcting Fe deficiency of agricultural crops. However, variable plant responses to iron sprays, ranging from no effect to defoliation, have often been described in the Fe-fertilization literature. Knowledge is still limited concerning the mechanisms of penetration of a leaf-applied, Fe-containing solution and the role of Fe in the leaf. The complex and multi-disciplinary character of the factors determining the effects of Fe sprays hinder the development of suitable foliar fertilization strategies, applicable under variable local conditions and for different plant types. This review describes some key factors involved on the process of penetration of a leaf-applied, Fe-containing solution before briefly analyzing the available foliar Fe-fertilization literature. Iron chemistry, leaf penetration, and plant-nutrition principles will be merged with the aim of clarifying the constraints, opportunities, and future perspectives of foliar Fe sprays to cure plant Fe deficiency.

Experiments to assess the re-greening and the distribution of leaf-applied iron (Fe) within the aerial organs were developed with tobacco (Nicotiana tabacum L.) plants. Fe (III)-citrate and Fe-dimerum acid were applied to a part of the leaf and plant re-greening was monitored for 6 weeks after treatment. Fluid Fe increments associated with foliar Fe application were measured within 3 days after application. Fe distribution from the site of application within the leaf and the untreated above-ground plant parts was evaluated. Leaf fluid Fe concentration was determined by a novel procedure based on Fe chelation by desferrioxamine E and high performance liquid chromatography separation on a reversed-phase column. The ferrioxamine E method enabled accurate determination of small amounts of Fe present in leaf fluid. Foliar Fe-dimerum acid and Fe (III)-citrate treatment to chlorotic tobacco plants induced new growth re-greening. It was concluded that the applied Fe-containing compounds penetrated the leaf, were distributed within the plant and that Fe supplied as both complexes could be utilized by the plant cell.

The influence of 0, 30, 60 and 120 mM NaCl on seedling emergence and early growth of Tamarindus indica L. was investigated under greenhouse conditions. The first seeds in the non-saline treatment emerged (E-1st) 7.5 days after sowing (DAS), 50 % of seeds had emerged (E-50) 8.4 DAS, and a maximum of 88.1 % of seeds had emerged 11.8 DAS. Addition of 30, 60 or 120 mM NaCl delayed E-1st by 1.5, 4.2 and 7.2 days, respectively, compared to the control. E-50 at 30 and 60 mM NaCl was achieved 10.7 and 15.7 DAS, respectively, whereas seeds at 120 mM failed to reach E-50. Seedling growth was not markedly affected by 30 mM, but progressively stronger inhibitory effects were observed within the 60 and 120 mM treatments.

The effects of reduced external water potentials (0, -0.3, -0.6, -0.90 and -1.30 MPa) generated by either NaCl or polyethylene glycol-6000 (PEG) on water uptake and germination characteristics of Tamarindus indica seeds were investigated under laboratory conditions. Water uptake and final germination percentage (G(F)) decreased, while number of days to 50% germination (D-50) and mean germination time (MGT) increased significantly with reducing osmotic potentials of both NaCl and PEG. At each iso-osmotic solution, PEG appeared to be more inhibitory to water uptake than NaCl, especially at the lowest water potential (-1.2 MPa). At this water potential, no germination was observed in both NaCl and PEG solutions. At all other treatments, NaCl resulted in lower G(F), and higher D-50 and MGT values than did iso-osmotic solutions of PEG. These results suggest that the main effect of PEG occurred via an inhibition of water uptake while detrimental effects of NaCl may be attributed mainly to accumulated toxic ions.

To study the salt tolerance of tamarind trees (Tamarindus indica L.), the effect of salinity on growth, photosynthesis, leaf chlorophyll concentration and mineral uptake of seedlings was investigated. Four-week-old seedlings were grown in a sand culture and were treated with different salt solutions for a period of 20 weeks. Treatments were prepared by adding 0, 20, 40, 60 and 80 mM NaCl to the nutrient solution.Plant growth was slightly affected by 20 and 40 mM NaCl but was markedly reduced on the 60 and 80 mM NaCl treatment. Foliar injuries (chlorosis) appeared only within the 60 and 80 mM variant. It was interesting that with increasing salinity concentration, leaf water content increased, indicating a salt-induced leaf succulence. This phenomenon was accompanied with an upward cupping of the leaflets.Increased NaCl salinity decreased the net photosynthesis rate from 5.6 to 0.5 mumol CO2 m(-2) s(-1) in 80 mM treatment compared with the control. Chlorophyll was also decreased with increasing salinity. Raising NaCl in the irrigation solution increased Na+ and Cl- concentration in the plant tissue. The uptake of the cations Ca2+ and K+ to the leaves was successfully maintained in the salt-stressed plants.The results indicate that T. indica seedlings tolerated a salinity concentration of up to 40 mM NaCl. Therefore, in the seedling stage, tamarind can be characterised as a moderate salt tolerant fruit tree species. (C) 2004 Elsevier B.V. All rights reserved.

Im Jahr 2003 wurden Sträucher der Kulturheidelbeersorten ‚Brigitta Blue‘ und ‚Nelson‘ (Vaccinium corymbosum L.) mit einem borhaltigen Pflanzenstärkungsmittel (Wuxal® Ascofol, 3% Bor) über das Blatt behandelt. Die Pflanzen wurden nach der Vollblüte an drei Terminen mit 0,5% Ascofol-Lösung gespritzt, wohingegen die Kontrollpflanzen Leitungswasser erhielten. Die Beerenernte erfolgte am 19. und 30. Juli, Blattproben wurden am 4. Juni und 7. August genommen. Der Borgehalt wurde in Blättern und Früchten bestimmt, bei den Früchten wurden zusätzlich der Ertrag und das Einzelfruchtgewicht ermittelt. Gleichzeitig wurde bei ‚Nelson‘ die potenzielle Boraufnahmerate pro Strauch errechnet.

A leaf re-greening trial using both Fe-sufficient and deficient Citrus madurensis Plants, was carried out over a period of 5 weeks. Attached green and chlorotic leaves were immersed in a 0.2% FeCl2 4H(2)O solution containing 0.05% Silwet L-7607 surfactant. Treatments were applied under light and dark conditions. Changes in leaf colour, chlorophyll content, and extractable Fe associated with FeCl2 4H(2)O supply were monitored. FeCl(2)4H(2)O application resulted in higher chlorophyll contents and extractable Fe in chlorotic leaves. At the end of the experiment, the treated chlorotic leaves achieved similar rates of leaf chlorophyll content, colour and Fe-content to those of Fe-sufficient control leaves.

The effect of salinity on growth, photosynthesis, leaf chlorophyll concentration and mineral uptake of baobab seedlings (Adansonia digitata L.) was investigated. Four weeks old seedlings were grown in sand Culture and were treated with different salt Solutions. Treatments were Prepared by adding 0, 20, 40, 60, and 80 mM NaCl to the nutrient Solution. Plant growth was strongly affected by the salt treatments. In the 20 mM NaCl variant, a reduction of 66% dry weight Occurred in comparison to the control plants. Foliar injuries (necrosis) and defoliation appeared within all salt treatments. However, with increasing salinity levels, leaf moisture content increased, indicating a salt-induced leaf succulence. Increased NaCl salinity decreased the net photosynthesis rate. Chlorophyll content of leaves at higher salinity levels was lower than at lower salinity levels. Raising NaCl in the irrigation solution increased Na+ and Cl- concentration in the plant tissue. Ca2+/Na+ and K+/Na+ ratios in the leaves were strongly reduced in salt treated plants. The results indicate that salinity significantly influences growth and metabolism of A. digitata seedlings. Therefore, in the seedling stage, baobab can be characterised as a very salt-sensitive species.

Africa has abundant wild plants and cultivated native species with great agronomic and commercial potential as food crops. However, many of these species, particularly the fruits and nuts, have not been promoted or researched and therefore remain under-utilized. Moreover, many of these species face the danger of loss due to increasing human impact on ecosystems.Sudan, as in many other African countries, is endowed with a range of edapho-climatic conditions that favor the establishment of many plant species, most of which are adapted to specific ecological zones. Among these plants is the baobab (Adansonia digitata L.) which is a fruit-producing tree belonging to the family Bombacaceae. The baobab has an exceedingly wide range of uses ranging from food and beverages to medicinal uses. Despite its potential, which is well recognized, very little is known about the tree phenology, floral biology, husbandry or genetic diversity.In this article, we have aimed to bring out detailed information on various aspects of its botany, ecology, origin, propagation, main uses, genetic improvement and especially its importance for nutrition and poverty alleviation in the Sudan.

The effect of varying Ca(NO3)2 supply (0, 5, 10 and 15mM) on growth, mineral uptake, leaf chlorophyll concentration and photosynthesis of NaCl-stressed (30 and 60mM NaCl) guava seedlings (Psidium guajava L.) was investigated. NaCl caused severe leaf damage (necrotic leaf margins). Dry matter production was lower in the 60mM treatment than in the 30mM NaCl variant. Addition of Ca(NO3)2 stimulated shoot growth more than root growth. Ca(NO3)2 supply increased leaf K+ and Ca2+ concentration, whereas the Na+ transport to the leaves was inhibited. There was a strong increase in the K+/Na+ ratio in leaves of Ca(NO3)2-treated seedlings. Leaf Cl− content was decreased by supplemental Ca(NO3)2 but Cl− was increased in shoots and roots. N concentration in all parts of the seedlings increased with enhanced Ca(NO3)2 supply. Leaf chlorophyll concentration and photosynthesis rate were low in NaCl-treated plants, but both factors were enhanced by 10mM of Ca(NO3)2. In general, moderate Ca(NO3)2 supply (10mM) had optimal effects on growth and metabolism of NaCl-stressed guava seedlings.

A number of under-utilized species with edible fruits have been identified during field studies in Central Sudan. Fruits of these indigenous species play a important role in the diet of people in the savanna belt of Sudan, especially during famines and food shortages. They have a considerable wide range of uses. Beside the fruits, the multipurpose trees provide a diversity of other important forest products. The species have great potential for future development. However, detailed scientific studies and trials are needed and a list of research priorities is given.

Tamarind (Tamarindus indica L.) seedlings were grown in sand culture under greenhouse conditions in order to examine the responses of growth, leaf mineral concentration and leaf gas exchange to increasing salinity levels. Four-months-old seedlings were exposed to a 10-week treatment, either with 0 (control), 40, 80 or 160 mM NaCl. Plant growth (fresh and dry weight) was slightly affected by 40 and 80 mM NaCl, but was markedly reduced on the 160 mM NaCl treatment. The root/shoot ratio increased by 24% when the NaCl concentration in the irrigation solution increased from 0 to 160 mM. With increasing salinity levels, leaf moisture content also increased, indicating a salt-induced leaf succulence. In plants treated with 160 mM NaCl, the concentrations of Na+ and Cl- in the leaf dry matter reached 0.91 and 0.92 mM g(-1), respectively. Leaf K+ decreased with higher salinity level, leading to higher Na+/K+ ratios. CO2 assimilation rate (A) diminished both with time of exposure and increasing salinity. T indica seedlings tolerated a salinity level of 80 mM NaCl, probably as the result of their ability to avoid excess ion accumulation through increased leaf volumes associated with succulence.

Seeds of tamarind (Tamarindus indica L.) were germinated following seven pretreatments, viz., control, mechanical scarification by scratching the region near the hilum on coarse sand paper or nicking it with a knife and acid scarification by immersion in concentrated sulphuric acid (H2SO4) for 15, 30, 45 and 60 minutes. Final emergence was 100% for all pretreatments, but days to first emergence (E-ist), days to 50% emergence (E-50) and mean emergence time (MET) varied significantly among them. The best germination response occurred with acid pretreatment followed by mechanical scarification. E-ist, E-50 and MET decreased as acid pretreatment time increased. Scratching on a coarse sand paper advanced the E-50 by 4.5 days and shortened the MET by 4.1 days compared to nicking.

Information on genotypic variation and horticultural potential of Tamarindus indica L., a multi-purpose evergreen tree found naturally in the Sudan, is lacking. Tn this study, we examined seed emergence behaviour and early seedling growth in three geographically diverse populations from the Sudan. The Central Sudan (CS) and the Eastern Sudan (ES) populations exhibited a nearly threefold variation between the largest and smallest seeds, whereas the Western Sudan (WS) population showed about twofold variation. Seed size was largest for WS (0.55 +/- 0.09 g), intermediate for CS (0.48 +/- 0.08 g) and smallest for ES (0.43 +/- 0.11 g). Tamarind seeds are generally slow to germinate as indicated by the allowance of 15 to 42 days from planting before the first and the last emergence count, respectively. Even though differences were not significant, the highest total percent emergence (97%) was recorded for WS population, followed by CS (92%) and ES (90%) populations. Seeds of WS population achieved E-50 (days to 50% emergence) two and three days earlier than ES and CS, respectively. They also showed more uniform emergence with a span of 19.7 days versus 24.7 and 25.3 days for ES and CS populations, respectively. Seedling vigour, evaluated in terms of seedling height, number of leaflets, total leaf area, total dry weight and leaf dry weight, was superior in WS population, while there were no measurable differences between CS and ES. Leaf photosynthetic characteristics did not vary among the three populations. Mean values for CO2 assimilation rate (A(CO2)), transpiration rate (E) and stomatal conductance (g(s)) were low but well within the range expected for evergreen woody species. In conclusion, for faster and uniform emergence and plant establishment in the nursery the WS population is the most suitable candidate.

Among the 3,000 species of the edible fruits in the tropics about 10% are more or less regularly cultivated as crop plants. This leaves more than 90% potentially useful, however, and may be gathered or cultivated to a limited extent for use as food or income source. One of these species is tamarind, Tamarindus indic L., an evergreen legume, native to the dry savannah of tropical Africa and growing wild throughout the Sudan. The much-appreciated qualities of the fruit and the adaptability of the tree to different soils and climates widened its distribution all over the tropics and subtropics. Despite this, very little is known about the tree phenology, floral biology, husbandry or genetic diversity. In this article we have aimed to bring out detailed information an various aspects of its origin, botany, ecology, propagation and cultivation, genetic improvement and main uses. In addition we reviewed the horticultural characteristics of tamarind and assessed its likely potential for further development in the Sudan.

The influence of NaCl and different levels of nitrogen supply (5, 10 and 15 mM Ca(NO3)(2)) on growth and physiological parameters of two Sudanese guava cultivars (white and red fruit flesh) were investigated. Under saline conditions shoot growth and leaf chlorophyll content In lava trees were reduced. However, moderate N supply improved these parameters. NaCl salinity reduced net photosynthesis rate (P-N) and transpiration (T) of both guava cultivars, but moderate nitrogen supply enhanced P-N and T. Stomatal resistance (R-s) was high under NaCl salinity conditions, whereas it was comparatively low for trees moderately supplied with nitrogen. The salinity-induced decrease of P-N in red guava is attributed to stomatal closure. In white guava this was rather an effect of non-stomatal factors.The xylem flow rate followed similar patterns for both cultivars and for all treatments except those supplied with NaCl only. The highest flow rates were noticed for both cultivars under moderate nitrogen supply.The red guava is supposed to possess a better salt tolerance compared to white guava.

In a greenhouse experiment rooted cuttings of mango rootstock '13/1' were grown in containers filled with quartz sand. The temperature inside the root containers was kept constantly at 22 degrees C. Containers were filled with stagnant water, whereby oxygen deficiency in the root zone was induced. Only plants with hypertrophied lenticells survived the treatment for more than 5 days. Flooding led to a decrease in leaf CO2 uptake. An enhanced stomatal resistance resulted in a reduced transpiration rate. Simultaneously root respiration and root growth decreased during flooding conditions. Root respiration paths were discriminated, proving an alternative path as a residual respiration.From the present investigation two selection criteria for flood tolerance in mango are deducted:1. Development of hypertrophied lenticells, which enable mango trees to transport oxygen from the atmosphere into the root.2. An alternative respiration path as well as residual respiration is present in roots of the mango rootstock '13/1'. We assume, that non-cytochrome pathways might play an important role in energy charge of roots under restricted soil oxygen.