Temperature Accumulation Research Articles

Index for harvesting time of white sapote (Casimiroa edulis Llave & Lex. ) cv. ‘Cuccio’

SummaryTo estimate a suitable index for harvesting time of white sapote (Casimiroa edulis Llave & Lex.), we investigated the changes in fruit and seed size, skin colour, seed colour, total soluble solids (TSS), sugars and polyphenol contents during fruit development in cv. ‘Cuccio’ pollinated at different times. Fruit growth showed a sigmoid curve and, therefore, was not a suitable index for maturity. Accumulated temperature (AT), which is a simple sum of hourly temperatures, or days after pollination (DAP) could be used as an index. An AT of approx. 120 103 degree hours (°C h) or 212 DAP were required for maturity of cv. ‘Cuccio’ fruit. There was a strong correlation between TSS content and percentage dry matter (DM) in pulp; therefore, a %DM ≥ 18.0% could also be used as an index of fruit maturity.Fruit skin colour, specifically the CIE a* value on the sun-exposed side, the b* value on the shaded side or seed colour were also good indicators of fruit maturity. Measurements of fruit skin colour using a colorimeter provides a convenient non-destructive detection method for fruit maturity.

Changes in sugars and acids in pitaya (Hylocereus undatus) fruitduring development

SummarySeasonal changes in skin colour, and sugar and acid contents were studied in pitaya (Hylocereus undatus Britt & Rose) fruits pollinated in July (Summer) and October (Autumn) on Ishigaki Island, Japan. Changes in skin colour pattern (a* and b* values), total soluble solids (TSS) and sugar contents exhibited a sigmoid pattern irrespective of the time of pollination, except for skin colour b* values in Autumn-pollinated fruit. In both groups, mature fruit had higher TSS contents in the centre of the fruit compared with other sections. Malic acid was the main acid in the fruit, with no clear seasonal pattern. Changes in glucose and fructose contents exhibited a similar pattern to that of TSS, but the values were higher in mature Autumn fruit than in mature Summer fruit, and differed among fruit sections. The differences tended to converge during late maturation when a* values and TSS contents reached a constant level. These results indicate that each a* value and TSS content could not be applied solely to a maturity index. By considering accumulated temperature (AT) from pollination (AT-growth) instead of days after pollination, changes in a* values and TSS contents were in good agreement, irrespective of pollination date. These values reached a plateau when fruit had received about 22,500°C AT-growth. In both series, the best harvesting time for white pitaya was when fruits had received approx. an additional 3,000ºC AT after the a* value had reached a plateau.

Leaf Emergence Rate and Temperature in Early and Late Spring Wheat Varieties.

Spring wheat varieties, early Haruyutaka and late Selpek, were grown under field conditions to find the relation between leaf emergence rate and temperature. Fourteen sowings were made at two week intervals from March 17 (S1) to September 13 (S14). Leaf expanding degree (Haun's scale) were measured daily, and shoot apices were checked every day to determine the date double ridge stage (DRS) appeared. Final leaf numbers differed by only one, although the first nine sowings ranged over four months from March (S1) to July (S9). Late variety Selpek always had one more leaf than early variety Haruyutaka for S1∼S9, suggesting that the final number of leaves was closely related to the earlobes of varieties. Leaf emergence rates with accumulated temperature (AT) were higher before than after DRS, and those before DRS decreased with delay in sowing time. The leaf expanding degree at DRS did not vary greatly among sowing times, but were synchronized with phenology. We established regressions before and after DRS for the relation between leaf expanding degree and AT. The coefficients (a) before DRS were higher than those after DRS for both varieties. In addition, their standard deviation was large so that inclinations of regressions before DRS differed with sowing time. We concluded that leaf emergence rate has a squared relation with mean temperature before DRS and a linear relation with mean temperature after DRS.

Compilation of an accumulated temperature database for use in an environmental information system

Accumulated Temperature (AT) is the integrated excess or deficiency of temperature about a fixed datum. It is a parameter obtained from temperature data, which can be used in models of crop growth. Accumulated temperature values can therefore be used by crop agronomists to model regional differences, for instance across Britain, and may prove increasingly important for assessing the impact of climate change. Previous studies have shown how knowing the response of a crop to a given AT regime allows the use of AT maps to demark areas suitable for growth. Thus, zones of suitability may be delineated on a national or regional basis for temperature sensitive crops such as maize. This work was undertaken to produce a flexible system for the generation of AT datasets for any specified threshold. These datasets can be used for comparison with AT data used in other parts of the world, and as a fundamental input to the assessment of land suitability. A software suite, ‘ATGen’ 1 1 Enquiries concerning the availability of ATGen may be directed to the authors. , has been developed for accumulating temperature data above and below user-selected temperature values for specified time periods.