The photosynthetic light response of commercial blackberry cultivars (Rubus L. subgenus Rubus Watson) is largely unexplored, although they are frequently grown in full sun. In this experiment, light response curves of floricane leaves from the cultivars Natchez, Apache, Navaho, and Von were examined throughout the following production stages: before shiny black fruit were present (before harvest, BH), during peak production of fruit (peak harvest, PH), and when most fruit had fallen from plants or any remaining were dull black (after harvest, AH). Each cultivar was evaluated between an irradiance of 2000 and 0 μmol·m–2·s–1. The estimated maximum photosynthetic rate (photosynthetic capacity, PNmax) was greater BH than AH across all cultivars, whereas ‘Natchez’ had a greater PNmax BH and PH compared with the other cultivars. During AH, all cultivars had a similar PNmax. The BH response curves declined under the highest irradiance measured, whereas the PH and AH response curves remained stable at similarly high irradiance. Of the four cultivars, Apache, Navaho, and Von appeared to be more photosynthetically limited than Natchez under increasing irradiance. Based on the cultivar-specific performance observed, blackberry response to light is a relevant trait that breeding programs should consider for improving cultivar adaptability to local and regional conditions.
A delay of leaf senescence resulting from variable fall climate may allow for additional nutrient resorption, and storage within reserve organs. Autumn leaves and reserve organs (<1 year shoots, >1 year shoots, stem above and below the graft union, the tap root, and fine roots) during dormancy of young peach trees were evaluated following warmer fall temperatures and limited soil moisture on two cultivars (‘Scarletprince’ and ‘Autumnprince’ both on GuardianTM rootstock) over two seasons. Four treatments were established for the two cultivars: (1) well-watered trees (100% ETc needs) in ambient outdoor temperatures; (2) water deficient trees (50% ETc needs) in ambient outdoor temperatures; (3) well-watered trees grown within a greenhouse; and (4) water deficient trees within a greenhouse. The greenhouse environment was on average 5°C warmer than the ambient outdoor temperature. Senescence was delayed on greenhouse-grown trees both years with leaf number and area similar in the greenhouse and outdoor environments prior to senescence. Across leaf samples, leaf nitrogen and phosphorus concentrations were lower within delayed senescence tree leaves while potassium was lower in leaves experiencing normal senescence. During dormancy, multiple reserve organs showed higher nitrogen, phosphorus, and potassium in trees with delayed senescence than normal senescence and similar increases were observed in water-deficient trees compared to well-watered trees. Phosphorus and potassium concentrations were also higher in multiple reserve organs within ‘Autumnprince’ trees compared to ‘Scarletprince’ trees. This study suggests variable climate conditions of increased temperatures or reduced soil moisture during autumn resulting in delayed senescence influence the process of nutrient resorption and increase nutrient storage within reserve organs.
Prevention of pests while maintaining viable seed during storage is often challenging for smallholder farmers in the tropics and subtropics. Investment in costly technologies or storage equipment is often unavailable or economically unreasonable, and alternative methods of seed storage can play a role in ensuring regional and global food security. This research evaluates whether or not vacuum sealing and locally available seed storage treatments are effective techniques to control cowpea bruchid (Callosobruchus maculatus). This research also assesses the effects of such techniques on the viability of stored Lablab (Lablab purpureus L.) seed in the humid tropics. Tested treatments included vegetable oil, pulverized bamboo charcoal, galangal powder, powdered detergent, a bleach solution, and carbaryl. Infested seed samples stored in northern Thailand under local treatment options and vacuum sealing were evaluated between May 2011 and May 2012 for bruchid presence, seed viability, and seed vigor. After 1 year of vacuum storage, seed viability was 77.6% compared with 66.5% under non-vacuum conditions. Over that period, vacuum storage successfully prevented bruchid population growth (4.9 compared with 123.3 insects per 50 seeds under non-vacuum conditions; F = 22.59, P < 0.001). By contrast, the oil treatment greatly reduced seed viability (1.3%), although it restrained bruchid population growth (3.5 compared to 97.0 insects per 50 seeds). Other local treatments (galangal powder, carbaryl, and bamboo charcoal) limited bruchid population growth (F = 8.37, P < 0.05) compared with the control, while maintaining seed viability. Seed germination duration was not affected by vacuum sealing and seed treatments but was rather influenced by changing environmental conditions throughout the trial. These seasonal changes also influenced overall insect lifecycle and seed metabolism. These results demonstrate that vacuum sealing and several locally available treatments provide novel, low-cost, appropriate seed storage options for local seed banks and smallholder farmers in the developing world, thus avoiding the use of locally rare or expensive chemicals, low temperature, or low moisture conditions.
Variable fall temperature and moisture conditions may alter leaf senescence of deciduous fruit trees, influencing carbon assimilation before dormancy and phenology the following spring. This study explored gas exchange of young peach trees (Prunus persica (L.) Batsch) when senescence proceeded normally or was delayed during the fall under two soil moisture treatments: Well-irrigated trees or water deficit. Results showed leaf carbon assimilation was similar between the senescence treatments, but whole tree assimilation was estimated to be greater in delayed senescence trees compared to normal senescence trees based on timing of defoliation and total leaf area. The effect of soil moisture on carbon assimilation was not consistent between years. Delayed sap flow and bloom time resulted as a consequence of delayed senescence the previous fall, but soil moisture did not affect spring phenology.
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