Intraspecific Variation in Pinus Pinaster PSII Photochemical Efficiency in Response to Winter Stress and Freezing Temperatures

As part of a program to select maritime pine (Pinus pinaster Ait.) genotypes for resistance to low winter temperatures, we examined variation in photosystem II activity by chlorophyll fluorescence. Populations and families within populations from contrasting climates were tested during two consecutive winters through two progeny trials, one located at a continental and xeric site and one at a mesic site with Atlantic influence. We also obtained the LT50, or the temperature that causes 50% damage, by controlled freezing and the subsequent analysis of chlorophyll fluorescence in needles and stems that were collected from populations at the continental trial site

Estudios ecofisiologicos sobre Pinus uncinata Mill. en el limite superior de la espacie

Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

Phenotypic plasticity in

• Carbon isotope composition (δ13C) is a complex trait involved in acclimation, adaptive processes and related to water use efficiency (WUE) and/or productivity. • To estimate the genetic variation in δ13C and growth (h), their relationship, and the genotype by environment interaction effect in both variables, we analyzed three Pinus pinaster populations and six to ten families per population, in two experimental trial sites and in two consecutive years. • δ13C increased in the drier site (from –27.15  ±  0.18 to –24.53  ±  0.22) and was more affected by environment (62% of variance) than by genotype. • All populations and families exhibited a high phenotypic plasticity in δ13C and increased WUE in the xeric site. • As expected, significant height differences between sites, years, populations and families were displayed. Smaller trees were associated to higher water use efficiency (δ13C) in both, mesic and xeric trial sites. • Aridity and continentality enhanced population differences in δ13C, therefore, in afforestation programs of arid and continental zones, the selection at the population level would be more efficient than at the family level. In the mesic site, the presence of a high genetic variation in δ13C and h between families allows the possibility of a selection for growth and water use efficiency within populations in sub-humid sites

Phenotypic plasticity in mesic populations of Pinus pinaster improves resistance to xylem embolism (P-50) under severe drought

The objectives of the study were to assess the phenotypic variation in the vulnerability to water stress-induced cavitation (estimated by P-50, or the xylem water potential which causes a 50% loss of conductivity) and the trade-offs between P-50 and related hydraulic traits, i.e., stem specific conductivity (K-s), slope of the vulnerability curve (slope), wood density and branch size. Variability was examined for six Pinus pinaster populations covering the latitudinal range of the species and plasticity was tested through two provenance-progeny trial sites (xeric/mesic). As expected, the overall values of P-50, K-s and branch size decreased in the xeric site. Variation in P-50 and K-s among populations was mainly the result of phenotypic plasticity, while wood density was genetically controlled and not affected by the environment. Stress conditions in the xeric site promoted a convergence in P-50 and K-s as a result of the high phenotypic plasticity of the populations from mesic origins. In the mesic site, the ranking of populations for cavitation resistance and hydraulic capacity was consistent with the geographic location of the seed source. Higher resistance to cavitation was related to lower K-s, branch size and slope, mainly at the population level, but also as a general trend across individuals. In a warmer and drier climate, there could be a potential selection of Pinus pinaster populations from mesic origins, which showed a great responsiveness and adjustment to drought conditions (similar or higher P-50 than the populations from dry origins), in addition to a high wood density and growth

Population heritabilities (<i>h²</i>) with non-zero significance, by <i>site</i> and <i>winter</i>.

<p>Abbreviations are the same as those in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0028772#pone-0028772-t002" target="_blank">Table 2</a>.</p

Summary of ANOVA significances.

<p><i>F</i>_v/<i>F</i>_m: maximum potential PSII efficiency. Φ_PSII: actual PSII efficiency. <i>qP</i>: photochemical quenching. <i>NPQ</i>: non-photochemical quenching. <i>Winter</i>: studied period (winter 2005–06, winter 2006–07). <i>Site</i>: location of the provenance-progeny trials. Num <i>DF</i>: number of degrees of freedom. Den <i>DF</i>: Denominator of degrees of freedom. Pr: Probability. <i>F</i>: F-values. Bold numbers denote values for which Pr>0.05.</p

Population variation in the photochemical parameters by site and winter.

<p>Bi-directional least squared means ± standard errors of the photochemical parameters for the populations (A: <i>Arenas</i>, O: <i>Oria</i>, M: <i>Mimizan</i>) present in the xeric (axis X) and mesic (axis Y) trial sites. Maximum potential (<i>F</i>_v/<i>F</i>_m) and actual (<b>Φ</b>_PSII) PSII efficiency and photochemical quenching (<i>qP</i>) and non-photochemical quenching (<i>NPQ</i>) after the cold (A1, B1, C1, D1) and warm winter (A2, B2, C2, D2) are shown. Diagonal lines indicate equal values at both sites. Values shown represent the mean of the values from 6 to 10 families from 3 populations.</p

Effects of Fe-chlorosis on the stomatal behaviour and water relations of field-grown peach leaves

We investigated the effects of Fe nutrition on the stomatal behaviour and water relations of peach leaves (Prunus persica (L.) Batsch, cv. Miraflores), under field conditions. Transpiration rates, net photosynthesis and water use efficiency were significantly lower in chlorotic leaves than in healthy green leaves. In the course of the day, the water potentials in healthy leaves strongly declined to –2.0 MPa, whereas in chlorotic leaves the minimum water potential was only -1.0 MPa. The hydraulic conductivity of the supplying xylem system was found to be significantly lower in chlorotic leaves than in green leaves. Chlorotic leaves were found to experience a significant transient opening of stomata after leaf abscission (Iwanoff effect), which was ascribed to the morphological changes found in epidermal and guard cells. In contrast, after leaf abscission stomata from green leaves gradually closed and were found not to be Iwanoff-reponsible. In healthy leaves, exposure of previously darkened leaves to high irradiation or withdrawal of CO2 induced a rapid increase of stomatal conductance, whereas stomata of chlorotic leaves did hardly react. These results show that in peach leaves Fe deficiency causes a broad range of physiological effects, which include, in addition to the well-documented reduction in photosynthetic performance, disturbances of plant water relations and the functionality of stomata

Percentages of variance by <i>site</i> and <i>winter</i> (%).

<p>Abbreviations are the same as those in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0028772#pone-0028772-t002" target="_blank">Table 2</a>.</p

Effects of Fe-chlorosis on the stomatal behaviour and water relations of field-grown peach leaves

We investigated the effects of Fe nutrition on the stomatal behaviour and water relations of peach leaves (Prunus persica (L.) Batsch, cv. Miraflores), under field conditions. Transpiration rates, net photosynthesis and water use efficiency were significantly lower in chlorotic leaves than in healthy green leaves. In the course of the day, the water potentials in healthy leaves strongly declined to –2.0 MPa, whereas in chlorotic leaves the minimum water potential was only -1.0 MPa. The hydraulic conductivity of the supplying xylem system was found to be significantly lower in chlorotic leaves than in green leaves. Chlorotic leaves were found to experience a significant transient opening of stomata after leaf abscission (Iwanoff effect), which was ascribed to the morphological changes found in epidermal and guard cells. In contrast, after leaf abscission stomata from green leaves gradually closed and were found not to be Iwanoff-reponsible. In healthy leaves, exposure of previously darkened leaves to high irradiation or withdrawal of CO2 induced a rapid increase of stomatal conductance, whereas stomata of chlorotic leaves did hardly react. These results show that in peach leaves Fe deficiency causes a broad range of physiological effects, which include, in addition to the well-documented reduction in photosynthetic performance, disturbances of plant water relations and the functionality of stomata