Inducing genetic variation in growth related characteristics of poplar germplasm, by producing inter-specific hybrids between P. alba and P. euphratica
by Mirzaie-Nodoushan H., Ghamari-Zare A., Tavousi Rad F., Yousefifard M. (2015)
Mirzaie-Nodoushan H., Forests and Rangelands Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Tehran, I.R. Iran.
Ghamari-Zare A., Forests and Rangelands Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Tehran, I.R. Iran.
Tavousi Rad F., Payam-Noor University, Isfahan, I.R. Iran.
Yousefifard M., Payam-Noor University, Tehran, I.R. Iran.
in Silvae Genetica 64, 5–6 (2015)
Crosses were made between two Populus species to create two hybrid groups, P. alba (f) * P. euphratica (m) and P. euphratica (f) * P. alba (m) . Aseptic immature hybrid seeds were first grown on MS medium. Hybrid seedlings were then acclimatized and grown in greenhouse conditions and transplanted to an experimental field.
Growth related characteristics were recorded on 307 three years-old seedlings of new inter-specific hybrids of six half-sib families, in order to assess possible potentials of the two hybrid groups.
Double nested analysis of variance revealed significant differences between the hybrid groups and siblings based on majority of the studied characters. The hybrid groups formed two distinct groups for some of the studied characteristics which implied maternal effects of inheritance on the traits.
The first hybrid group had more but shorter and closer branches than the second group. Adaxial stomata number for the two hybrid groups varied between 4.7 to 123. Whereas, there were no such strong differences between vegetative characteristics of the two groups.
The second hybrid group had a very condense layer of white fuzz on its abaxial leaf surface, inherited from its female parents. This may lead to suggest some kinds of photosynthesis and respiration functions such as leaf sub-stomatal chambers’ functions for the mentioned fuzzy trichomes of the second hybrid group and their female parental species, P. alba.
In essence, 307 new divergent poplar hybrid genotypes were produced by which ecological zone of poplar species could be extended in the country as well as high yielding genotypes would be promising.
Plants tightly control stomatal aperture in response to various environmental changes.
A drought-inducible phytohormone, abscisic acid (ABA), triggers stomatal closure and ABA signaling pathway in guard cells has been well studied.
Similar to ABA, methyl jasmonate (MeJA) induces stomatal closure in various plant species but MeJA signaling pathway is still far from clear.
Recently we found that Arabidopsis calcium dependent protein kinase CPK6 functions as a positive regulator in guard cell MeJA signaling and provided new insights into cytosolic Ca2+-dependent MeJA signaling.
Here we discuss the MeJA signaling and also signal crosstalk between MeJA and ABA pathways in guard cells.
This study tests two predictions from a recently proposed model for stomatal responses to humidity and temperature. The model is based on water potential equilibrium between the guard cells and the air at the bottom of the stomatal pore and contains three independent variables: gs0, Z and Θ.
gs0 is the value of stomatal conductance that would occur at saturating humidity and will vary among leaves and with CO2 and light. The value of Z is determined primarily by the resistance to heat transfer from the epidermis to the evaporating site and the value of Θ is determined primarily by the resistance to water vapour diffusion from the evaporating site to the guard cells.
This leads to the two predictions that were tested. Firstly, the values of Z and Θ should be constant for leaves of a given species grown under given conditions, although gs0should vary among leaves and with light and CO2. And secondly, the ratio of Z to Θ should be higher in leaves having their stomata in crypts because the distance for heat transfer is greater than that for water vapour diffusion.
Data from three species, Nerium oleander, Pastinaca sativum and Xanthium strumarium support these two predictions.
Plant resistance to drought has long been thought to be associated with the ability to maintain transpiration and photosynthesis longer during drought, through the opening of stomata. This premise is at the root of most current framework used to assess drought impacts on land plants in vegetation models.
We examined this premise by coupling a meta-analysis of functional traits of stomatal response to drought (i.e. the water potential causing stomatal closure, ψclose) and embolism resistance (the water potential at the onset of embolism formation, Ψ12), with simulations from a soil-plant hydraulic model.
We found that ψclose and Ψ12 were equal (isometric) only for a restricted number of species, but as Ψ12 decreases, the departure from isometry increases, with stomatal closure occurring far before embolism occurs.
For the most drought resistant species (Ψ12<-4.2 MPa), Ψclose was remarkably independent of embolism resistance and remained above -4.5 MPa, suggesting the existence of a restrictive boundary by which stomata closure must occur.
This pattern was supported by model simulations. Indeed, coordinated decrease in both ψclose and ψ12 leads to unsuspected accelerated death under drought for embolism resistant species, in contradiction with observations from drought mortality experiments.
Overall our results highlight that most species have similarity in stomatal behavior, and are highly conservative in terms of their water use during drought. The modelling framework presented here provides a baseline to simulate the temporal dynamic leading to mortality under drought by accounting for multiple, measurable traits.
Prof Jennifer McElwain (right) and Dr Claire Belcher, with plants in a carbon dioxide atmosphere chamber, as part of the programme for experimental atmosphere and climate, at UCD Thornfield. Photograph: Eric Luke
‘Our climate is changing at a faster pace than ever before in geological history’
Research Lives: Prof Jennifer McElwain, UCD School of Biology and Environmental Science
“Paleo” means old and “botany” means the scientific study of plants. So I study fossil plants, many of them older than the dinosaurs. These ancient plant remains can tell us a lot about climate change in the past.
Where is the most interesting site that you have collected plant fossils?
Astartekløft, in east Greenland within the Arctic Circle. A team of five of us were helicoptered there in July 2000 for a National Geographic expedition. We spent four wonderful weeks digging up 200-million-year-old fossils, avoiding polar bears and eating Parmesan cheese and salami sausage.
We collected more than 4,500 fossil plants and spent the next decade trying to piece together the ancient landscapes that the fossils revealed, and how plants in the past responded to natural global warming events caused by volcanism.
How do you figure out ancient plant survival tactics?
Using the fossils we worked out how many species were around in Greenland over 200 million years ago, then we reconstructed the climate of the time and tracked the fossil species to examine which went extinct and which survived global warming.
We discovered that generalist plant species survived better than specialists, which were more likely to go extinct as the climate warmed. A good example of a generalist is a species that does not rely on another species to reproduce (that other species may go extinct!) but uses the wind to reproduce.
We also saw that when there is a small amount of carbon dioxide in the atmosphere, leaves have lots of tiny openings or pores called stomata. However, when the amount of carbon dioxide in the atmosphere increases, the plants tend to develop far fewer stomata.