Seed developmental temperature regulation of thermotolerance in lettuce

Lettuce (Lactuca sativa L.) seeds can fail to germinate at temperatures above 24 degrees C, The degree of thermotolerance is thought to be at least partly related to the environment under which the seed developed. In order to study the effects of temperature during seed development on subsequent germination, various lettuce genotypes were screened for their ability to germinate at temperatures ranging from 20 to 38 degrees C. Seeds of the selected genotypes 'Dark Green Boston' and 'Valmaine' (thermosensitive), 'Floricos 83', 'Everglades', and PI 251245 (thermotolerant) were produced at 20/10, 25/15, 30/20, and 35/25 degrees C day/night temperature regimes in plant growth chambers. Seeds were germinated on a thermogradient bar from 24 to 36 degrees C under 12 h light/dark cycles. As germination temperature increased, the number of seeds that failed to germinate increased. Above 27 degrees C, seeds matured at 20/10 or 25/15 degrees C exhibited a lower percent germination than seeds that matured at 30/20 or 35/25 degrees C. Seeds of 'Dark Green Boston' and 'Everglades' that matured at 30/20 OC exhibited improved thermotolerance over those that matured at lower temperatures. Seeds of 'Valmaine' produced at 20/10 degrees C exhibited 40% germination at 30 degrees C, but seeds that matured at higher temperatures exhibited over 95% germination. Germination of 'Valmaine' at temperatures above 30 degrees C was not affected by seed maturation temperature. The upper temperature limit for germination of lettuce seed could thus be modified by manipulating the temperature during seed production. The potential thermotolerance of seed thereby increased, wherein thermosensitive genotypes became thermotolerant and thermotolerant genotypes (e.g., PI 251245) germinated fully at 36 degrees C. This information is useful for improving lettuce seed germination during periods of high soil temperature, and can be used to study the biology of thermotolerance in lettuce

Seed physiology: Consultant final report IICA/EMBRAPA PROCENSUL II

Series Publicacoes Miscelaneas A4/BR (IICA) no. 89-041. 24 páginasThe document explains that the resultant research is important because it gives an opportunity to offer very low cost plant propagules that are disease free, and that carry new genetic traits. The glyphosate transformation will be used as a model to confer other resistances to this species. Furthermore, the sweet potato system of direct field delivery of somatic embryos can be used as a model for other equally important crops of the tropics and semitropics as previously mentioned

Preferência da broca-das-cucurbitáceas [Diaphania nitidalis Cramer, 1782 (Lepidoptera: Pyralidae)] por cultivares de pepineiro em ambiente protegido Pickleworm [Diaphania nitidalis Cramer, 1782 (Lepidoptera: Pyralidae)]preference for cucumber cultivars in greenhouse

A broca-das-cucurbitáceas (Diaphania nitidalis) é uma praga de grande importância em diversas culturas, principalmente do pepineiro. Esta espécie pode apresentar preferência em relação a determinadas cultivares quanto à sua alimentação e até mesmo oviposição. Nesse sentido, o presente estudo objetivou avaliar a ocorrência desta praga em frutos de seis cultivares de pepineiro, em ambiente protegido. As cultivares Patton, Victoria, Premier, Vlaspik e Napoleon apresentaram, respectivamente, 50%, 43,75%, 37,50%, 34,37% e 25,87% dos frutos brocados. A cultivar Marinda apresentou resultado promissor, com apenas 10,37% dos frutos com presença de larvas de D. nitidalis.<br>The pickleworm (Diaphania nitidalis) is a major pest on different crops, particulary on cucumber. This species has shown a preference for determined cultivars to its feeding and oviposition habits. Thus, the aim of this study was to evaluate the occurence of D. nitidalis larvae in fruits of six cucumber cultivars in greenhouse. The cultivars Patton, Victoria, Premier, Vlaspik and Napoleon showed, respectively, 50%, 43.75%, 37.50%, 34.37% and 25.87% of bored fruits. Promising results were obtained with the cultivar Marinda, which showed only 10.37% of bored fruits

Proceedings of the World Conference on Horticultural Research (WCHR), Rome, Italy, 17-20 June 1998

In recent years, photo-responsive hydrogels reported in the literature have been synthesised by co-polymerisation of N-isopropylacrylamide (NIPAAM) with spiropyran(SP) derivatives. This approach requires external protonation of the hydrogels in order to induce re-swelling, typically by immersing the hydrogel in strongly acidic environments1-3. Moreover, re-swelling times are long, typically up to several hours. These disadvantages have restricted the use of photo-actuated hydrogels to applications that employ single-use methods. Recently, we reported that the addition of acrylic acid copolymerised within the hydrogel provides an internal source of protons that allows photo-actuation in neutral pH environments4. The polymerisation solvent has been shown to directly influence the morphology of the hydrogel, by producing porous hydrogels of different pore sizes5. This has an impact on the diffusion path length for water molecules moving in/out of the hydrogel matrix, thus improving the swelling and shrinking kinetics of the hydrogel6. In this study photo-actuator hydrogels were generated using a N-isopropylacrylamide-co-acrylated spiropyran-co-acrylic acid (p(NIPAAM-co-SP-co-AA) copolymer, in a 100-1-5 mole ratio. Different ratios of organic solvent:water (tetrahydrofran(THF), dioxane and acetone) were used as the polymerisation solvent. Varying the volume ratio of the solvent mixtures, resulted in hydrogels with different pore sizes and therefore different extent of swelling/shrinking and actuation kinetics. For example, when THF:water (4:1 v:v) was used as polymerization solvent, a remarkable contraction in hydrogel size of up to 50% was obtained after four minutes of white light irradiation. Optimising these hydrogels by varying the polymerization solvent has resulted in faster and more reproducible shrinking and reswelling cycles