Morpho-anatomical and cytological analysis of tomato fruit during development exposed to drought

Abstract

The aim of this study was to study the morpho-anatomical and cytological parameters of tomato fruit pericarp structure that underlie in plant responses to optimal water regime and deficit irrigation conditions (i.e., the effects of PRD and DI treatments). For this research we used two tomato genotypes (Lycopersicon esculentum Mill.): Wild-type Ailsa Craig (WT) and its mutant flacca, with reduced ability of synthesis of the plant hormone abscisic acid (ABA). Plants were grown under controlled conditions in three different plant growth substrate water regimes: control plants were optimally irrigated (FI), plants exposed to DI treatment were watered with plenty of water about 60% less evenly distributed over the entire root system, whereas in plants exposed to PRD irrigated with about 30% less water than FI treatment, provided that the total quantity of water added in only one half of the root system, irrigation wet and dry side was shifted when volumetric soil water content had decreased in dry side to 15-18%. The study included the determination of the differences between genotype and irrigation treatment effect on the main morphological parameters of the fruit, and anatomical characteristics of pericarp during development. Cytological traits of pericarp were studied using two methods: separation of cells in pectinase solution and analysis of pericarp cells on cross sections, with special emphasis on the characterization of the pericarp cell layers and their development, starting from the third day after the full flowering stage (daa) to the mature fruit stage. The results showed that in wild-type PRD treatment can save the water for irrigation without reducing the fruit diameter and fresh fruit weight, pericarp weight, and pericarp cell size, while on the other side DI treatment with a smaller amount of water for irrigation resulted in significantly smaller fruits as result of reduction in mass of placenta and pericarp tissue, as well as a significant reduction in the pericarp cell size and number. The effect of PRD and DI on the development of the pericarp in the wild type was expressed in a significant reduction in the size of the cells of the outer part of the mesocarp, built of cells that have formed from the outside subepidermal layers and layers E2 E3, E4, I3. The positive effect of PRD treatments on fruit growth is expressed in the stimulation of growth or in increase of the cell size in the layers that arise from the lower subepidermal layer, and the pericarp mass was same as in the FI treatment, as well as an increase in percentages of dry matter in the fruit resulted in same fruit fresh weight and diameter for both, PRD and FI treated wild type plants...

Cilj ovog istraţivanja je bio da se detaljno prouĉe morfo-anatomski i citološki parametri graĊe perikarpa ploda paradajza koji se nalaze u osnovi reakcije biljaka na optimalne uslove vodnog reţima i na tretmane redukovanog navodnjavanja (tj. efekata PRD i DI tretmana). Za istraţivanja su korišćena dva genotipa paradajza (Lycopersicon esculentum Mill.): divlji tip Ailsa Craig (WT) i njegov mutant flacca, koji ima smanjenu sposobnost sinteze biljnog hormona abscisinske kiseline (ABA). Biljke su gajene u kontrolisanim uslovima u tri razliĉita vodna reţima supstrata za gajenje: kontrolne biljke su optimalno zalivane (FI), biljke izloţene DI tretmanu su zalivane sa oko 60% manjom koliĉinom vode ravnomerno rasporeĊenom na ceo korenov sistem, dok su biljake izloţene PRD tretmanu zalivane sa oko 30% manjom koliĉinom vode od FI tretmana, s tim što je celokupna koliĉina vode dodavana samo u jednu polovinu korenovog sistema, a zamena strana je vršena kada sadrţaj vode u nezalivanoj strani padne ispod 15-18%. Ispitivanja su obuhvatila utvrĊivanje razlika izmeĊu genotipova kao i uticaj tretmana zalivanja na osnovne morfološke parametre ploda i anatomske karakteristike perikarpa plodova tokom razvoja. Citološke karakteristike perikarpa su prouĉavane primenom dve metode: razdvajanjem ćelija primenom rastvora pektinaze i analizom popreĉnih preseka, sa posebnim akcentom na karakterizaciju slojeva ćelija perikarpa i njihov razvoj poĉev od trećeg dana nakon potpunog otvaranja cveta do faze zrelog ploda. Rezultati su pokazali da je kod divljeg tipa PRD tretmanom moguće uštedeti vodu za zalivanje bez redukcije preĉnika i sveţe mase ploda, mase perikarpa i veliĉine ćelija, dok je sa druge strane primenjena manja koliĉina voda za zalivanje u DI tretmanu rezultovala znaĉajno manjim plodovima zbog redukcije mase placente sa semenima i perikarpa, kao i zbog znaĉajnog smanjenja veliĉine i broja ćelija perikarpa. Uticaj PRD i DI na razvoj perikarpa kod divljeg tipa se ogleda u znaĉajnoj redukciji veliĉine ćelija spoljašnjeg dela mezokarpa, graĊenom od ćelija koje su nastale od spoljašnjeg subepidermalnog sloja E2 i slojeva E3, E4, I3. Pozitivan efekat PRD tretmana na rast ploda se ogleda u stimulaciji rasta ili povećanju veliĉine ćelija pojedinih slojeva koji nastaju od donjeg subepidermalnog sloja, pa je masa perikarpa ploda ista kao i u FI tretmanu, kao i u povećanju procenta suve mase u plodu rezultujući time da plodovi divljeg tipa u PRD tretmanu imaju istu sveţu masu i preĉnik kao i u FI tretmanu kod divljeg tipa...