Coexistent Heteroblastic Needles of Adult Pinus canariensis C.Sm. ex DC. in Buch Trees Differ Structurally and Physiologically

Great variation in shape and size between primary (juvenile) and secondary (adult) needles, so-called leaf-heteroblasty, occurs in several Pinus species. Most of them loss primary needles during the juvenile-to-adult transition of the tree. An exception to this is Pinus canariensis (a Canary Islands endemism) in which basal resprouting twigs of adult trees frequently wear both primary and secondary needles. Taking advantage of this extraordinary study-case-species, we conducted an exhaustive comparison of both needle types through quantitative analyses of needle anatomy, photochemical performance, gas exchange, and resistance to extreme dehydration and to extreme needle temperature. We hypothesized that primary needles would show lower investment to leaf structure but higher photosynthetical efficiency. Primary needles had less stomatal density and thicker and less wettable cuticles. In cross section, primary needles showed smaller structural fraction (e.g., percent of hypodermis, endodermis and vascular tissue) and higher fraction of photosynthetic parenchyma. Significant differences between primary and secondary needles were not found in net carbon assimilation not in their leaf mass area values. Interestingly, secondary needles showed higher electron transport rate, and they were additionally much more efficient in retaining water under severe and controlled desiccant conditions. When subjected to extreme temperatures (−10° to +50 °C), primary needles recovered better their photochemical efficiency than secondary needles, after +46° and +48 °C heat-shock treatments. Our results indicate that both needle types broaden the diversity of physiological responses against environmental constrains in basal twigs of adult P. canariensis trees. Considering that this is a fire-resistant and resprouting species, this advantage could be particularly useful after a drastic environmental change such a fire or a gap opening in the forest.

Different responses to environmental factors in terpene composition of Pinus heldreichii and P. peuce: Ecological and chemotaxonomic considerations

Many studies show the influence of the environment on terpene composition, but not many of them deal with the terpene composition variability in correlation with environmental factors in Pinus. We chose two endemic species ? P. heldreichii Christ. (Bosnian pine) and P. peuce Griseb. (Macedonian pine) ? two relict and (sub)endemic species of the Balkan peninsula. They mainly form pure stands but can appear in mixed populations, most commonly with each other. These species belong to different subgenera and thus differ greatly, especially in needle anatomy. ?-pinene, limonene and germacrene D predominated in Bosnian pine leaf oleoresins, while Macedonian pine oleoresin contained high amounts of ?-pinene. Furthermore, there were three chemotypes present in Bosnian, and only one in Macedonian pine. Oleoresins of Bosnian pine did not show correlation with climate, however, its composition changed in response to geological substrate type. Macedonian pine oleoresin showed a high correlation with the climate but changed only a little in response to geological substrate type. The oleoresin profiles showed strong species-dependent composition and variability. However, since each species expressed different responses to tested environmental conditions, it is important to take into consideration these variables when analyzing natural populations of the species.

The effect of mistletoe (Viscum album) on branch wood and needle anatomy of Scots pine (Pinus sylvestris)

ABSTRACTMistletoes are hemi-parasitic plants growing on many tree species. They grow on the tree branches or trunk of a tree and form root-like structures called haustoria that penetrate into the tree, taking up water and mineral nutrients. Mistletoe is capable of causing a variety of effects to its hosts, including changes in wood formation and leaf development. We investigate and discuss the effects of pine mistletoe (Viscum album ssp. austriacum, Santalaceae) on branch wood and needle anatomy of Scots pine (Pinus sylvestris, Pinaceae). Parasitized and nonparasitized branches of Scots pine were sampled from host tree crowns of trees growing on the same site. Branches were taken from mid-crown facing south. They were cut at 2 cm proximal and 2 cm distal to the mistletoe on each host branch and at the corresponding position in the case of uninfected branches from the same host. The wood anatomy at proximal and distal parts and the parts at the corresponding position in the non-parasitized section was compared. The anatomy of one-year-old needles from both parasitized and non-parasitized branches was also compared. Mistletoe had significant influences on wood and needle anatomy. The major changes were the decreases in the double wall thickness, lumen area, tangential lumen area and radial lumen area of the tracheids in the wood and a decrease in vascular area in the needles. These results help to understand how mistletoe acts on its host.

Warming and elevated ozone differently modify needle anatomy of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris)

Acclimation of conifer needle anatomy to climate change is poorly understood. We studied needle anatomy, shoot gas exchange, current-year shoot length, and stem diameter growth in Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) seedlings exposed to elevated ozone (1.35× to 1.5× ambient concentration) and elevated temperature (0.9–1.3 °C + ambient temperature) alone and in combination for two exposure seasons in two separate open-field experiments in central Finland. Pines grew also at two soil nitrogen levels. In spruce, warming increased mesophyll intercellular space and reduced gas exchange and shoot growth and made needles narrower and the epidermis and hypodermis thinner. In pine, warming made needles bigger, increased shoot and stem growth, stomatal row number, and proportions of vascular cylinder, phloem, and xylem and reduced the proportion of mesophyll. These responses indicate that pine benefited and spruce suffered from moderate warming. Ozone caused a thickening of epi- and hypo-dermis and a lower stomatal conductance in both species, reduced stomatal density in spruce, and increased proportions of phloem, xylem, and sclerenchyma and reduced growth in pine. Ozone responses suggest increased oxidative stress defense. Stomatal responses were affected by interactions of elevated temperature and ozone in both species. Nitrogen availability modified ozone and temperature responses, particularly in the vascular tissues in pine.

Phenotype features in juvenile populations of Picea abies and their growth

The young populations of Norway spruce (Picea abies) can be evaluated in terms of both variability in the quantitative characteristics and share of different phenotypes according to the needle types. A set of two-years-old seedlings produced in the nursery and several populations of natural regeneration in the Krkono&scaron;e Mts. and the Kru&scaron;n&eacute; hory Mts. were evaluated using the needle anatomy, size and colour. The tree height growth was measured simultaneously. The growth was related to some needle features. Four basic anatomical types of needles were distinguished in the mountain Norway spruce seedlings: flat needles, intermediate needles, inversion type and sclerotized needles. The growth of natural regeneration populations is mainly correlated with the needle width and the <br /> length/width ratio. The population variability according to growth can be related to the variability of some phenotype characteristics. This relationship differs in natural regeneration and planting. &nbsp;

Needle anatomy suggests hybridization between the relict turfosa form of Pinus sylvestris L. from the Gązwa peat bóg and typical Scots pine

The aim of this study was to characterize the turfosa form of <em>Pinus sylvestris</em> from the Gazwa peat bog reserve in terms of 16 anatomical needle traits and to determine whether pines with a typical morphotype inhabiting the peat bog have been so successful thanks to hybridization with the unique tufosa ecotype. Investigations were conducted on three phenotypic groups of Scots pine growing in the peat bog. The first two groups consisted of 30 tufosa trees at the age of 117-217 years and 20 trees at the age of 30-85 years. The third group consisted of typical pines represented by 10 trees at the age of 20-55 years. In total 30 trees of typical pine, surrounding the peat bog, at the age of 100-150 years served as outgroup. Descriptive statistics, analysis of variance with the F test, Tukey's test, and a number of multivariate analyses were used to estimate differences between the studied groups of trees based on 16 anatomical needle characteristics. The old turfosa form from the Gazwa reserve proved to be a unique and relict peat bog pine, as it was shown by the differences in 10 analyzed needle traits in comparison to pine with a typical morphotype growing in the areas surrounding the peat bog. The young typical pines have adapted to conditions found in the peat bog owing to hybridization with the turfosa forms. The young turfosa trees differed from the old turfosa trees and also they have probably been of a hybrid origin. The old turfosa form from the Gazwa reserve is a threatened ecotype due to its hybridization with pines from the population surrounding the peat bog.

The effects of male and female Arceuthobium americanum (lodgepole pine dwarf mistletoe) infection on the relative positioning of vascular bundles, starch distribution, and starch content in Pinus contorta var. latifolia (lodgepole pine) needles

The lodgepole pine dwarf mistletoe, Arceuthobium americanum Nutt. ex Engelm., is a dioecious angiosperm that parasitizes conifers in western Canadian forests, causing significant yearly timber loss. A striking consequence of dwarf mistletoe infection is a marked reduction in the size of the needles located distal to the infection. The purpose of this work was to use microscopy, cytochemistry, and biochemical analysis to determine whether this reduction was associated with changes in needle anatomy and (or) starch content. Furthermore, we wanted to investigate whether these potential changes were affected by the gender of the infecting dwarf mistletoe plant. We developed a ratio (R) that evaluated the position of the two vascular bundles relative to the size of the needle, and found that bundles from male-infected trees were positioned significantly closer together than in needles from female-infected or uninfected trees (p < 0.05). Using the periodic acid – Schiff’s (PAS) reaction for cytochemical identification of starch in situ, we determined that needles from uninfected trees had abundant starch grains compared with needles from infected trees; colourimetric analysis for total starch content corroborated our PAS data. This is the first report of this phenomenon in lodgepole pine, and further supports the use of needle characteristics to assess tree health.