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We measured the effects of planting density (238, 317 and 476 trees ha), irrigation (fully irrigated control vs. deficit irrigation) and their interaction on the vegetative growth, yield and irrigation water use efficiency (IWUE) of young olive trees during three seasons. In the water deficit treatment, irrigation was applied when midday stem water potential (SWP) dropped below −2.5 MPa; SWP of controls was maintained between −1.2 and −1.5 MPa. Across irrigation treatments, oil yield at high density (968 kg ha) was 70 % higher than at low density. Reduction in oil yield due to deficit irrigation was not significant compared to control (501 vs. 664 kg ha). IWUE at lower tree density averaged 1.5 kg ha mm, increased by 50 % in intermediate density and by 57 % at the highest density. Deficit irrigation increased IWUE twofold with respect to controls. IWUE responded to the interaction density × irrigation whereby the highest IWUE (4.6 kg ha mm) was obtained at highest density and deficit irrigation. IWUE was nonlinearly related to seasonal water stress integral ( $$S\psi$$ ), where maximum efficiency corresponded to 180 MPa days. The negative correlation between fruit water concentration and $$S\psi$$ highlights the potential benefit of deficit irrigation of increasing oil extractability. The positive outcomes of increasing the density (higher oil yield) and deficit irrigation (higher IWUE, lower water concentration in fruit) need to be weighed against the long-term effect on vegetative growth. Under our conditions, three seasons of water deficit reduced crown and trunk size by 35 % in relation to fully irrigated. [ABSTRACT FROM AUTHOR]

Both water deficit and elevated temperature are likely to accelerate shrivelling in Shiraz berries with consequences for fruit yield and quality. The process of shrivelling is partially related to mesocarp cell death and it has been proposed that enhancement of berry flavour and aroma also correlates with mesocarp cell death. However, the combined effects of water deficit and elevated temperature on berry shrivelling, mesocarp cell death and berry sensory traits are unknown. We tested the hypotheses that (1) the effects of water deficit and elevated temperature on the dynamics of mesocarp cell death and shrivelling are additive, and that (2) faster cell death, as driven by warming and water deficit, negatively contributes to grape sensory balance. Using open-top chambers to elevate day and night temperature, we compared heated vines against controls at ambient temperature. Thermal regimes were factorially combined with two irrigation regimes, fully irrigated and water deficit, during berry ripening. The dynamic of cell death was characterised by a bilinear model with three parameters: the onset of rapid cell death and the rate of cell death before and after the onset of rapid cell death. Statistical comparison of these three parameters indicated that there was not interaction between water and temperature on the dynamics of berry mesocarp cell death. Warming advanced the onset of cell death by ~9 days ( P = 0.0002) and water stress increased the rate of cell death in the period post onset ( P = 0.0007). Both water stress and elevated temperature increased the proportion of cell death and shrivelling at harvest. An interaction between water deficit and elevated temperature was found whereby the onset of berry net water loss was advanced by elevated temperature under water deficit but not in the fully irrigated treatment. Sensory traits typical of ripened berries were associated with higher cell death; however, warming and water deficit hastened ripening and altered the balance of berry sensory traits. [ABSTRACT FROM AUTHOR]

Population-level compensation occurs 'when herbivore attack on one individual allows another individual to grow more rapidly'. This form of compensation was investigated in high and low density cotton crops subjected to three treatments: (i) undisturbed controls, (ii) uniformly damaged, in which all plants were damaged, and (iii) non-uniformly damaged, in which every second plant was damaged. Damaged plants had their vegetative buds manually removed to simulate damage by Helicoverpa spp. (Lepidoptera). Removal of vegetative buds did not reduce seed cotton production per unit ground area. In uniformly damaged crops, compensation was essentially the result of profuse branching after release of apical dominance and activation of axilary buds. In non-uniformly damaged crops, population level mechanisms acted that involved strong plant-plant interactions. At both plant densities, undamaged plants grown alongside damaged neighbours accumulated more root and shoot biomass and produced more seed cotton than undamaged plants in uniform crops. Different degrees of symmetry in the relationship between damaged and undamaged neighbours lead to different degrees of compensation, viz. seed cotton production of non-uniformly damaged crops ranged from 98 to 125% of that in controls. At high plant density, neighbour status also affected flowerbud initiation and/or retention. Changes in competitive relationships as well as early detection of and response to neighbour status were likely involved in these responses. [ABSTRACT FROM AUTHOR]

Damaged cotton plants in which reproductive organs were manually removed to simulate shedding induced by Helicoverpa spp. (Lepidoptera) were compared with undamaged controls grown under contrasting availability of resources. Plant growth and partitioning were analysed and fruit mass was taken as a measure of compensation. Under high availability of resources (low plant density, high fertility) damaged plants had a large potential compensatory capacity due to increased vegetative growth that enhanced their ability to assimilate carbon and nitrogen with respect to undamaged controls. These plants shifted from vegetative to reproductive growth when they were allowed to set fruit in the recovery period. Actual compensation was complete, however, only when the duration and conditions of the recovery period were favourable. Under multiple stresses (high plant density, low fertility, low temperature), damage triggered a marked increase in the allocation of biomass to roots which was not reversed when plants were allowed to set fruit. The apparent shift in the allocation pattern of damaged plants under stress-which matches well the survival strategy described for many perennials-probably restricted compensatory fruit growth. [ABSTRACT FROM AUTHOR]