For Macadamia integrifolia Maiden and Betche var. 849, we compared four limb removal strategies of varying style and severity over 4 years, in terms of effects on yield, on the distribution of light, and new vegetative shoots, racemes and fruit within the canopy. Limb removal reduced yields. The reduction corresponded with the severity of pruning, not with the style of pruning. Limb removal had little impact in the medium term on light penetration to the orchard floor. Within the canopy, shoot production and raceme production were inversely related. Shoot production was favoured by high light conditions; raceme production occurred predominantly in areas of heavy shade, with 49% of racemes produced at canopy locations receiving less than 2% full daylight, and 94% produced at locations receiving less than 16% full daylight. Most flowering appeared to occur on wood more than 3 years old. The capacity of different parts of the canopy to support fruit set and retention increased with proximity to the more irradiated parts of the canopy, but fruit production was still high deep within the lower part of the canopy, with 50% of fruit produced at canopy locations receiving less than 2% full daylight, and 90% produced at locations receiving less than 16% full daylight.
The relationship between the cycle of flush development and temperature is not well described for Tahitian lime, or citrus species in general. We pruned trees over 16 months in the humid subtropics of northern New South Wales (NSW), and monitored post-pruning flush development over two cycles, in terms of flush commencement and flowering. We also recorded temperatures over this period. The time from pruning to the emergence of the first post-pruning flush was correlated with mean daily temperature, with emergence being slower at cooler temperatures. Emergence times ranged from 11 to 39 days. The time between the commencement of the first and second flushes was also correlated with mean daily temperature, with slower development of the first flush at cooler temperatures. The duration of the first flush varied from 41 to 128 days. There was more flowering on the first than the second flush (16% of shoots versus 3%). There was no flowering on flushes that commenced in the warmer months, from November to March. The temperature threshold for flowering appeared to be at a mean daily temperature of ~20°C. Regressions between flush development and temperature were used to estimate the effects of climate warming from 1963–1971 to 2003–2011, using long-term temperature records. The warming decreased bud emergence time by 1.6 days in winter and 1 day in summer; and reduced the time from the first to the second flush by 11.8 days in winter and 9.2 days in summer. The results for Tahitian lime were similar to those for other recurrent flushing trees.
Triple-labelled nutrient solution was used to compare the effects of seven root-infecting fungi on uptake of K, Ca and P by wheat. Plants grown in sand or hydroponic culture were transferred to solutions that contained42K,45Ca and32P for 24 h, then dried, ashed and digested in 6M HCl. To distinguish radiation emitted by42K,45Ca and32P plant digests were counted on two channels of a liquid scintillation counter immediately and 7 days later, after the decay of42K radiation. Plants infected byGaeumannomyces graminis took up and translocated less K, Ca and P to their shoots than uninfected plants. Other root-infecting fungi had little effect on uptake of these ions
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