An efficient H2O direction for Citrus spp. trees in any cropping state of affairs requires accurate quantitative information on H2O usage. Interpretation of the H2O dealingss of most Citrus spp. cultivars is hard due to the happening of stomatous oscillations whose beginning is non good known and that cause trying jobs in irrigation direction ( Dzikiti et al. 2006 and 2008 ; Wright 2008 ) .
Vegetative growing, and peculiarly leaf development and root diameter, of orange trees ( Citrus sinensis ( L. ) Osbeck ) is peculiarly susceptible to H2O scarceness ( Dzikiti et al. 2006 ; Aiyelaagbe and Orodele 2007 ) , and workss respond to drought by alterations in gas exchange, phytohormonal balance and polyamine contents ( Wang and Liu 2009 ) . Furthermore, internal H2O storage contributed significantly to the day-to-day entire foliage transpiration in this species ( Dzikiti et al. 2006 and 2008 ) . Garc & A ; iacute ; a Petillo et Al. ( 2004 ) compared the effects of different irrigation volumes on ‘Washington Navel ‘ orange outputs during a five-year period ( 0, 50 % , 100 % and 150 % ETc ) . To use these interventions, one irrigation trickle line per tree row, with drippers, of 2, 4 and 6 L h-1 capacity, separated 1 m apart were used for the 50 % , 100 % and 150 % ETc interventions. Another intervention received the same sum of H2O as 100 % ETc, but with two trickle lines spaced 1 m apart per tree row and 2 L h-1 drippers, and showed important additions in entire fruit output and fruit size if compared to 100 % ETc. The application of the PRD irrigation method ( 50 and 100 % ETc ) to orange trees was evaluated over two turning seasons by Dzikiti et Al. ( 2008b ) . The writers found that stomatous conductance in the PRD interventions was lower than in the control fully-watered intervention but no important alterations in norm fruit output were found between the two PRD interventions and the control workss. Sing RDI, it has been demonstrated that the irrigation cut-off during the concluding fruit growing and adulthood procedure ( phase III ) in orange ( curriculum vitae. ‘Lane late ‘ grafted on ‘Carrizo ‘ Citroncirus webberi ) reduces midday SWP, does non cut down fruit output, and increases entire soluble solids and titrable sourness, without changing fruit quality and the concluding adulthood index ( P & A ; eacute ; rez-P & A ; eacute ; rez, Robles and Bot & A ; iacute ; a 2009 ) . On the contrary, Garc & A ; iacute ; a-Tejero et Al. ( 2010 ) found that RDI applied during the blossoming and early fruit-growth stages ( curriculum vitae. ‘Navelina ‘ grafted onto ‘Carrizo ‘ Citroncirus webberi ) , both output and fruit quality ( in footings of entire soluble solids and titrable sourness ) were negatively affected.
Other Citrus species appear to hold responses against drouth emphasis similar to those found in orange. Huang et Al. ( 2000 ) examined the growing alterations generated by mild drought emphasis on potted tangerine trees ( Citrus reticulata Blanco, curriculum vitae. ‘Zhuju ‘ ) by H2O keep backing during early juice pouch enlargement phase. They observed that fruit growing was inhibited by drought emphasis but a greater H2O consumption was caused by a lower H2O potency in fruits of stressed workss, probably due to a higher H2O loss from fruit to transpirating foliages during H2O deficit and some active adaptative physiological responses ( osmotic accommodation and cell wall loosening ) of fruit to this emphasis. In satsuma Citrus reticulata trees ( Citrus unshiu Marc. ) a positive relationship between flower-bud initiation and the degree of endogenous works endocrines was found as a consequence of the application of mild ( predawn LWP = from -0.5 to -1.0 MPa ) and moderate drouth emphasis ( predawn LWP = from -1.5 to -2.0 MPa ) ( Yoshita and Takahara 2004 ) . The consequences indicate that gibberellin degrees were enhanced by terrible drouth emphasis, higher in the foliages from the subdivisions that produce fewer flowers during flower-bud initiation periods, whereas the degrees of indole-3-acetic acid were higher in the foliages from the subdivisions that produced more flowers during the season when flower-buds develop. As in C. sinensis, the measuring of maximal day-to-day bole shrinking is a suited and dependable index of the degree H2O shortage reached by workss of other Citrus species, such as lemon ( C. limon ( L. ) Burm. fil. ) and rancid orange ( C. aurantium L. ) ( Ortuno et al. 2009 ) .
Other Mediterranean fruit species
Pomegranate
Pomegranate trees ( Punica granata L. ) are considered as a harvest with a high degree of tolerance to dirty H2O shortage. Pomegranate cultivation is chiefly confined to the Torrid Zones and semitropicss and it grows good in waterless and semi-arid climes, but it is now widely cultivated in Mediterranean ( Hepaksoy et al. 2009 ) . In Spain, for illustration, its civilization is concentrated in the south E, where fresh H2O available for agribusiness is really scarce. The H2O dealingss of field grown pomegranate trees grown under different trickle irrigation governments were late investigated by Intrigliolo et Al. ( 2011 ) . These writers observed that during spring and fall, noon SWP was non important different between irrigation interventions while there were considerable differences in leaf photosynthesis and stomatous conductance, proposing a near-isohydric behavior of Punica granatum trees. This means that workss command gas exchange such that daytime H2O content is about unaffected by dirt H2O shortages, and that other mechanisms ( e.g. , ABA production and signaling ) can be responsible for the ordinance of works H2O position. There is small cognition about the response of Punica granatum to drought, and in general to abiotic emphasiss. In one of the few researches, Bhantana and Lazarovitch ( 2010 ) studied the evapotranspiration, harvest coefficient and growing of two immature Punica granatum assortments under salt emphasis, corroborating that this species exhibits a high tolerance under inauspicious environmental conditions. If compared to other irrigation techniques, drip irrigation is the best manner to increase fruit output and works growing of Punica granatum, as its root system is peculiarly inhibited by H2O stagnancy, whereas fruit output is non significantly influenced by the degree of irrigation ( Sulochanamma, Yellamanda Reddy and Subbi Reddy 2005 ) . Furthermore, irrigation of Punica granatum trees is really of import, as fruit splitting and snap can happen, unless they are on a regular basis irrigated. Excess lacrimation or inordinate rain during the ripening period may besides do similar harm to the fruits ( Hepaksoy et al. 2009 ) . Finally, vitamin C, cut downing sugar and entire sugar content were observed in fruit of drought-stressed workss ( Lawand, Patil and Patil 1992 ) .
Pistachio
Pistachio is a harvest autochthonal to western and cardinal Asia but its cultivation has spread to the Mediterranean part, which has become its 2nd most of import Centre of diverseness after Iran. The importance of Pistacia spp. is non limited to this merchandise entirely: the trees ‘ great tolerance to drought and their ability to boom in hapless dirt conditions make them peculiarly suited for forestry programmes on fringy lands, where they can besides stand for a beginning of extra income for local husbandmans ( Padulosi et al. 1998 ; Sedaghat 2008 ) . Pistachio cultivation requires the usage of rhizome because grafting is the lone signifier of vegetive extension, therefore the pick of the most effectual rhizomes plays a cardinal function, as they determine the physiological and biochemical responses of the workss to drought ( Ranjbarfordoei 2000, 2002 ; Gij & A ; oacute ; n et Al. 2010 ) . The utmost drouth opposition of Pistacia spp. enables husbandmans in waterless and semi waterless lands to turn this nut without irrigation ( Kaska 2002 ) . Despite the economic importance of comestible Pistacia vera ( Pistacia vera L. ) , really small information is available on its food demands and H2O demands. Potassium ( K ) fertilisation is found to be effectual in increasing foliage K position, nut output and quality in this species, and K uptake occurs chiefly during the nut fill period ( Zeng, Brown and Rosecrance 1998 ) . Tajabadipour, Sepaskhah and Maftoun ( 2006 ) , studied the effects of three irrigation frequence and five K degrees on the works H2O dealingss and growing of three Pistacia vera cultivars ( ‘Badami ‘ , ‘Ghazvini ‘ , and ‘Sarakhs ‘ ) , establishing that the dry weights of foliages, roots and roots significantly decreased with increasing irrigation intervals, whereas K application had no important consequence on LWP, osmotic potency, and turgor potency. From a molecular point of position, Yakubov et Al. ( 2005 ) observed the accretion of dehydrin-like proteins both in the blossoming bud and in the bark of immature Pistacia vera stems, proposing that they may hold a function in drouth and cold tolerances, every bit good every bit functioning as storage proteins. An irrigation experiment affecting Pistacia vera ( P. vera, curriculum vitae. ‘Kerman ‘ , on P. terebinthus rhizomes ) was performed by Gij & A ; oacute ; n et Al. ( 2009 ) over a four-year period to find the consequence of RDI ( at 65 % and 50 % of control irrigation ) on nut output and quality. The growing season was divided into three phenological phases: phase I – from shooting until the terminal of rapid nut growing ; phase II – from maximal nut size until the beginning of meats growing ; and present III – from the beginning of meats growing until crop. The workss subjected to RDI were merely significantly stressed during phase II, demoing midday LWP of around -1.4 MPa. The application of RDI resulted in smaller nut diameter and lower entire output. Furthermore, trees subjected to RDI had a entire output and per centum of split nuts similar to those of the controls, and did non demo the normal surrogate bearing form of this tree harvest. The writers concluded that this rootstock-scion combination presents a high grade of drought-resistance and could be expeditiously applied in pistachio cultivation.
Prickly pear
Opuntia, besides known as ‘nopales ‘ or ‘paddle cactus ‘ , is a genus in the household Cactaceae. The most commonly culinary species belonging to this genus is the Indian fig Opuntia ficus-indica ( L. ) Miller, normally known as ‘prickly pear ‘ . This species is native to Mexico but it is besides found in southern Europe and northern Africa, where it contributes, like olive tree, to the typical Mediterranean landscape. The bristly pear tree is able to hive away high H2O sums in its succulent variety meats and it has a really broad ( even though non deep ) root system with dense and quickly renewing root hairs, that allow workss to expeditiously utilize highly low rainfall ( Mulas and Mulas 2004 ) . Prickly pear has a CAM photosynthesis and therefore maintains the pore of mature cladophylls open merely in the dark, but, under highly terrible H2O shortages, the pore remain closed all twenty-four hours long and so the workss use to photosynthesize merely the CO2 derivation from the respiration ( Nieddu et al. 1997 ) . Pimienta-Barrios et Al. ( 2000 ) evaluated the effects of seasonal fluctuation in temperature, irradiation, and dirt wet content on the photosynthetic rates of bristly pear. They demonstrated that this species is strongly adapted to arid climes and that root photosynthesis by cladophylls ( root modified for photosynthesis that looks like foliages ) allows workss to repair C to be used during the periods when dirt H2O content is really low. Drought significantly affects cladode morphology and inhibits new cladophyll production, as these latter have a C4-photosynthesis and open the pore during the twenty-four hours, with attendant H2O losingss ( Nieddu et al. 1997 ) . Furthermore, cladophylls can make temperatures 15 & A ; deg ; C higher than the environmental 1s, keeping their enzymatic activities up to 60 & A ; deg ; C.
The fruit output of bristly pear is rather low, probably due to restricting environmental factor ( low H2O sums, dirts with low degrees of organic affair ) , but a fertilisation up to 160 kilograms ha-1 determines a output addition and a high fruit quality ( Mulas and Mulas 2004 ) . Mulas and D’hallewin ( 1997 ) estimated that fruit output in irrigated workss is at least two creases higher than that of un-watered workss, due to higher fruit figure per cladophyll and non to additions in fruit weight. On the other manus, irrigated workss presented an addition in fruit Peel thickness, that reduced the juice per centum, and in seed weight ( Mulas and D’hallewin 1997 ) . Snyman ( 2006 ) aimed at quantifying the effects of drought emphasis on the growing of tap roots, side roots and rain roots of the species Opuntia ficus-indica ( L. ) ( curriculum vitae. ‘Morado ‘ , with green cladophylls ) and O. robusta Wendl. ( curriculum vitae. ‘Monterey ‘ , with bluish cladophylls ) , both holding comestible fruits. They planted one-year-old cladophylls in root boxes and pots in a nursery. Puting the cladophylls flat on the dirt, more areoles came in contact with the dirt, and each areole composite formed on mean three roots. From the analysis of the growing of tap roots, side roots and rain roots, and from the informations on root size and denseness O. robusta appeared to be less sensitive to drought than O. ficus-indica.
Loquat
Loquat ( Eriobotrya japonica Lindl. ) , besides called Nipponese Vangueria infausta or Nipponese plum, is a semitropical evergreen tree harvest autochthonal to southeasterly China but really good adapted to mild-winter countries of the Mediterranean basin ( Hueso and Cuevas 2008 ) . Drought stresses causes important lessenings in leaf enlargement rate, country and photosynthetic pigments, and in stomata size, and increases in pore denseness ( Luo et al. 2007 ) . Both shortage irrigation during the full season and post-harvest RDI from mid-May through the terminal of August ( decrease of 20 % H2O demands, with H2O nest eggs established around 1450 m3 ha-1 yr-1 ) were successfully applied in this species ( Hueso and Cuevas 2008 ) . It was observed that post-harvest RDI normally advances full bloom 10-20 yearss, leting to obtain a more precocious and valuable output, whereas the effects of uninterrupted shortage irrigation is less noticeable ( Hueso and Cuevas 2008 ; Fern & A ; aacute ; ndez, Hueso and Cuevas 2010 ) . On the reverse, output and fruit quality are non affected for the different shortage irrigation schemes. The optimum month for the application of post-harvest RDI in Japanese medlar seem to be July, due to the positive effects on the promotion of bloom and crop day of the month and its harmlessness for flower development, even thought every RDI applied in the period June-August ( with a H2O decrease up to 75 % ) does non act upon negatively fruit set, size and output ( Cuevas et al. 2007 ) .
Decisions and positions
A new attack in fruit grove direction is imposed by the environmental exigencies that are taging this recent period ( e.g. , soil debasement as a consequence of eroding and desertification, H2O deficit, greenhouse consequence ) . In semi-arid Mediterranean lands, the acceptance of agricultural systems by agencies of conventional, non-sustainable techniques causes the decrease of dirt organic affair, groundwater taint, dirt lack of mineral elements ( in peculiar P and N ) , alkalinization/salinization, and nutritionary instabilities in workss. On the other manus, the recent researches on the physiology of fruit trees and on dirt chemical and biological birthrate in fruit groves have revealed that sustainable and advanced dirt direction systems, with a peculiar accent on irrigation, let to obtain an optimum works nutritionary equilibrium, avoid foods accretion and leaching hazards, better irrigation efficiency, and prevent dirt eroding and root asphyxia. As highlighted in this chapter, the definition of appropriate irrigation techniques ( e.g. , SDI, RDI, PRD ) and soil direction in Mediterranean fruit groves are indispensable necessities for continuing dirt quality, positively impacting dirt microbic activity and birthrate, and keeping top outputs of high quality. Sing the scientific, practical and socio-economical importance of these subjects, and the increasing environmental exigencies related to H2O scarceness, a conspicuous figure of surveies is expected in the following old ages. At the minute, it is clear that the application, optimisation, invention of sustainable agricultural techniques with a low negative environmental impact can let to retrieve or increase the normal degrees of entire birthrate in agro-ecosystems, with positive effects on both dirt and output quality.
