Comparison of water status indicators for young peach trees

We measured a series of physiological and physical indicators and compared them to xylem sap flow, to identify the most sensitive and reliable plant water status indicator. In the growing season of 1998, 4-year-old peach trees (Prunus persica Batsch cv. 'Suncrest', grafted on 'GF 677' rootstock) were studied under two irrigation treatments, 25 l day(-1) and no irrigation, and during recovery. Trials were conducted near Pisa (Italy) in a peach orchard situated on a medium clay loam soil and equipped with a drip-irrigation system (four 4 l h(-1) drippers per tree). Measurements of leaf water potential (Psi(W)), stem water potential (Psi(S)), and leaf temperature (T-1) were taken over 5 days (from dawn to sunset) and analyzed in conjunction with climatic data, sap flow (SF), trunk diameter fluctuation (TDF) and soil water content (SWC). Physiological indicators showed substantial differences in sensitivity. The first indication of changes in water status was the decrease of stem radial growth. TDF and SF revealed significant differences between the two irrigation treatments even in the absence of differences in pre-dawn leaf water potential (pdPsi(W)), up until now widely accepted as the benchmark of water status indicators. Irrigated trees showed a typical trend in SF rate during the day, while in non-irrigated plants the maximum peak of transpiration was anticipated. Measurements of water potential showed Psi(S) to be a better indicator of tree water status than Psi(W). T-l was found to have poor sensitivity. In conclusion, we found the sensitivity of the indicators from the most to the least was: TDF > SF rate > SF cumulated = pdPsi(W) = Psi(S) > mdPsi(W) > T-l

The involvement of indoleacetic acid in paradormancy and sylleptic shoot development of grafted peach trees and hybrid rootstoks.

The physiological mechanisms controlling the induction of lateral branching, which is part of the expression of growth vigour, were investigated in two hybrid rootstocks (GF 677 and Mr.S. 2/5) widely used in peach [Prunus persica (L.) Batsch] cultivation that were grafted to a nectarine scion (cv. 'Big Top'). As expected, field-grown rootstocks showed different degrees of vigour and also induced distinct patterns of growth on the scion. The higher the rootstock vigour, the greater the number and length of lateral shoots developed by the scion. Hence, the growth vigour affected paradormancy and we hypothesized that auxin, which is known to suppress axillary bud development following bud break when transported basipetally along the shoot, might mediate rootstock-induced branching in the top of the tree. The role of indole-3-acetic acid as a hormonal signal in lateral branching was assessed by analysing its concentration in apical and axillary buds collected from growing shoots, both intact and at different times after apex removal. Shoot pruning was used as a means to force axillary buds to overcome paradormancy, assuming that their responses would reflect their intrinsic capacity of resuming growth. The development of lateral buds of both grafted scions and intact rootstocks was positively correlated with the respective auxin concentration and following shoot apex removal the relationships became stronger. Therefore, auxin may be responsible for mediating the expression of growth vigour. The invigorating effect of a rootstock would then be dependent on its ability of inducing high auxin levels in axillary buds. The hormone would act directly within bud tissues to stimulate their growth following bud break

Observations on nine peach rootstocks grown in a replant soil

‘Flavorcrest’ peach [Prunus persica (L.) Batsch] trees grafted onto nine rootstocks (four hybrids of peach, almond and P. davidiana: Barrier 1, Cadaman, GF 677, and Sirio; five plum clones: Ishtara, Julior, Mr.S.2/5, Penta and Puebla) were grown in a replant soil in the Pisa Province (Italy). Trees were planted on January 1998 at 4.5 x 2.0 m spacing and trained to a free spindle (‘fusetto’). Measurements of the vegetative growth, yield, phenology and fruit quality of each tree were recorded annually. Results of trunk cross-sectional area, size and volume of the canopy, summer and winter pruning weights showed that Barrier 1, GF 677 and Cadaman were the most vigorous rootstocks followed by plum clones and then Sirio. Sirio and plum clones had earlier harvest times compared to the other rootstocks; whereas fruit ripening on GF 677 and Barrier 1 was delayed. Cumulative yield was highest on Cadaman and GF 677 and lowest on Penta, Sirio and Mr.S. 2/5, while yield efficiency was highest on Sirio, Julior, Puebla, Cadaman and Ishtara. Fruit size was highest on Barrier 1, GF 677 and Ishtara and lowest on Julior and Sirio. Flesh firmness was highest on vigorous rootstocks (Barrier 1, Cadaman and GF 677) while a lower soluble solids content was found only on Barrier 1 rootstock. Finally, there was a higher mortality rate, for Ishtara, Julior and Sirio, due to replant disease

Espectroscopia do visível e infra-vermelho próximo para estimar sólidos solúveis e firmeza de polpa em função da época de colheita em pêssegos

O objetivo deste estudo foi estabelecer modelos de calibracao para estimar solidos soluveis e firmeza da polpa de forma nao destrutiva em pessegos 'Chimarrita', 'Maciel', 'Eldorado' e 'Jubileu' observando o efeito da epoca da colheita das frutas sobre estes modelos. Para isto, no primeiro ano de execucao foi utilizado o espectrofotometro NIR-Case (SACMI) no qual foram estabelecidas as equacoes de calibracao para cada cultivar a partir das avaliacoes por metodos nao destrutivos e destrutivos e, posteriormente, testou-se o desempenho destes modelos atraves do procedimento da validacao com a observacao dos resultados coeficiente de determinacao (R2) e erro padrao dos valores previstos (SEP). No segundo ano de experimento utilizando o mesmo equipamento e metodologia, datas de colheitas ao longo da maturacao dos pessegos foram estipuladas e nestas foram desenvolvidos modelos de calibracao para cada cultivar estudada. De acordo com os resultados obtidos, conclui-se que os modelos propostos para avaliacao da qualidade das frutas foram satisfatorios para predizer o teor de solidos soluveis nas cultivares em estudo, e o mesmo resultado nao foi observado em relacao a firmeza de polpa no primeiro ano de avaliacao. No segundo ano observou-se que os valores dos parâmetros estatisticos referentes a validacao dos modelos estabelecidos se alteram ao longo das diferentes epocas de colheita, mas com valores de R2 e SEP aceitaveis para estimar os teores de solidos soluveis em todas as cultivares e para o parâmetro firmeza de polpa apenas para as cultivares Eldorado e Jubileu os valores foram considerados satisfatorios

Variations in physiological and biochemical traits of oak seedlings grown under drought and ozone stress

Despite the huge biodiversity characterizing the Mediterranean environment, environmental constraints, such as high sunlight and high temperatures alongside with dry periods, makes plant survival hard. In addition, high irradiance leads to increasing ozone (O3 ) concentrations in ambient air. In this era of global warming, it is necessary to understand the mechanisms that allow native species to tolerate these environmental constraints and how such mechanisms interact. Three Mediterranean oak species (Quercus ilex, Q. pubescens and Q. cerris) with different features (drought tolerant, evergreen or deciduous species) were selected to assess their biometrical, physiological and biochemical responses under drought and/or O3 stress (80-100 nl l(-1) of O3 for 5 h d(-1) for 77 consecutive days). Leaf visible injury appeared only under drought stress (alone or combined with O3 ) in all three species. Drought × O3 induced strong reductions in leaf dry weight in Q. pubescens and Q. cerris (-70 and -75%, respectively). Alterations in physiological (i.e. decrease in maximum carboxylation rate) and biochemical parameters (i.e. increase in proline content and build-up of malondialdehyde by-products) occurred in all the three species, although drought represented the major determinant. Q. ilex and Q. pubescens, which co-occur in dry environments, were more tolerant to drought and drought × O3 . Quercus ilex was the species in which oxidative stress occurred only when drought was applied with O3 . High plasticity at a biochemical level (i.e. proline content) and evergreen habitus are likely on the basis of the higher tolerance of Q. ilex

Cross‐Talk between Physiological and Metabolic Adjustments Adopted by Quercus cerris to Mitigate the Effects of Severe Drought and Realistic Future Ozone Concentrations

Global climate change represents a moving target for plant acclimation and/or adaptation, especially in the Mediterranean basin. In this study, the interactions of severe drought (20% of the effective daily evapotranspiration) and O3 fumigation (80 ppb, 5 h day−1, for 28 consecutive days) on (i) photosynthetic performance, (ii) cell membrane stability, (iii) hydric relations, (iv) accumulation of compatible solutes, and (v) lipophilic antioxidant compounds were investigated in young Quercus cerris plants. In addition to the typical drought-induced stomatal closure, imposition of water withholding dramatically influenced the profile of stress-associated metabolites, i.e., abscisic acid (ABA), proline, and lipophilic antioxidants. However, plants were not able to delay or prevent the negative effects of water deficit, the greatest impacting factor in this study. This translated into a steep decline of photosynthetic efficiency, leaf hydration, and membrane fluidity and permeability. When water stress was coupled with O3, plants orchestrated cross-talk among ABA, proline, and sugar in fully-expanded mature leaves, partially leading to a premature senescenc

Living in a Mediterranean city in 2050: broadleaf or evergreen ‘citizens’?

The predicted effects of global change (GC) will be exacerbated in the more densely populated cities of the future, especially in the Mediterranean basin where some environmental cues, such as drought and tropospheric ozone (O3) pollution, already mine seriously plant survival. Physiological and biochemical responses of a Mediterranean, evergreen, isohydric plant species (Quercus ilex) were compared to those of a sympatric, deciduous, anisohydric species (Q. pubescens) under severe drought (20% of the effective daily evapotranspiration) and/or chronic O3 exposure (80 ppb for 5 h dayâ1 for 28 consecutive days) to test which one was more successful in those highly limiting conditions. Results show that (i) the lower reduction of total leaf biomass of Q. ilex as compared to Q. pubescens when subjected to drought and drought à O3 (on average â59 vs â70%, respectively); (ii) the steeper decline of photosynthesis found in Q. pubescens under drought (â87 vs â81%) and drought à O3 (â69 vs â59%, respectively); (iii) the increments of malondialdehyde (MDA) by-products found only in drought-stressed Q. pubescens; (iv) the impact of O3, found only in Q. pubescens leaves and MDA, can be considered the best probes of the superiority of Q. ilex to counteract the effect of mild-severe drought and O3 stress. Also, an antagonistic effect was found when drought and O3 were applied simultaneously, as usually happens during typical Mediterranean summers. Our dataset suggests that on future, the urban greening should be wisely pondered on the ability of trees to cope the most impacting factors of GC, and in particular their simultaneity

Application of Vis/Nir spectroscopy to establish peach ripening as affected by rootstock

The objective of this paper was to monitor peach ripeness of “Chimarrita” and “Maciel” cultivars, grafted on different rootstocks, using the pulp firmness parameter, as an indicator of harvest time through equipment based on Vis/Nir spectroscopy. The orchard was installed in 2005, has a "V" conduction system with spacing of 5.0 x 1.5 m, and the cultivars are grafted on seven rootstocks: “Capdeboscq”, “Flordaguard”, “Nemaguard”, “Okinawa”, “Tsukuba”, “Umezeiro” and “Viamão”. After harvesting, the fruits were evaluated by the NIR CASE spectrophotometer, establishing categories of pulp firmness, between 40N and 60N for fruits consumed in a long term and <40N for immediate consumption. The analyzed rootstocks alter the peach ripeness of the “Chimarrita” and “Maciel” cultivars. The “Umezeiro” rootstock anticipates harvest for the “Chimarrita” cultivar. The “Nemaguard”/ “Maciel” combination provides fruits with a superior harvest period than the other ones evaluated. The Vis/Nir Spectroscopy is a useful tool to monitor the harvest of “Chimarrita” and “Maciel” cultivars

Losing the warning signal: Drought compromises the cross-talk of signaling molecules in quercus ilex exposed to ozone

Understanding the interactions between drought and acute ozone (O3) stress in terms of signaling molecules and cell death would improve the predictions of plant responses to climate change. The aim was to investigate whether drought stress influences the responses of plants to acute episodes of O3 exposure. In this study, the behavior of 84 Mediterranean evergreen Quercus ilex plants was evaluated in terms of crosstalk responses among signaling molecules. Half of the sample was subjected to drought (20% of the effective daily evapotranspiration, for 15 days) and was later exposed to an acute O3 exposure (200 nL L-1 for 5 h). First, our results indicate that in well-water conditions, O3 induced a signaling pathway specific to O3-sensitive behavior. Second, different trends and consequently different roles of phytohormones and signaling molecules (ethylene, ET; abscisic acid, ABA; salycilic acid, SA and jasmonic acid, JA) were observed in relation to water stress and O3. A spatial and functional correlation between these signaling molecules was observed in modulating O3-induced responses in well-watered plants. In contrast, in drought-stressed plants, these compounds were not involved either in O3-induced signaling mechanisms or in leaf senescence (a response observed in water-stressed plants before the O3-exposure). Third, these differences were ascribable to the fact that in drought conditions, most defense processes induced by O3 were compromised and/or altered. Our results highlight how Q. ilex plants suffering from water deprivation respond differently to an acute O3 episode compared to well-watered plants, and suggest new effect to be considered in plant responses to environmental changes. This poses the serious question as to whether or not multiple high-magnitude O3 events (as predicted) can change these cross-talk responses, thus opening it up possible further investigations