Effects of temperature on growth and stress hardening development of phytotron-grown seedlings of Aleppo pine (Pinus halepensis Mill.)

Abstract

-One year-old Pinus halepensis seedlings, grown in peat-vermiculite-pine bark mix in 200 cm 3 containers, were moved to a growth chamber and submitted to a progressive decrease of temperature and photoperiod for three months. Morphological parameters and nutrient and non-structural carbohydrate content were measured. Root growth potential, freezing and drought resistance tests were assessed. Although height growth stopped when the minimum temperature fell below 9 ºC, shoot dry weight increased further. Needle potassium concentration and K/N ratio increased progressively and significantly throughout the trial. This may be attributed to potassium accumulation. As height growth stopped, physiological changes were detected in shoot nitrogen and soluble sugar concentrations, root activity and hydraulic conductance maintenance. Nevertheless, cold and drought resistance tests, as well as root regeneration potential, did not reveal any sign of plant stress tolerance until the minimum temperature decreased to 8 ºC and photoperiod to 9 h. This latter temperature may be considered to be the threshold for Pinus halepensis to accumulate the required chilling hours that make seedlings suitable for afforestation purposes. At least, more than 330 chilling hours (£ 8 ºC) are required to reach a minimum level of stress hardiness. The Fv/Fm chlorophyll fluorescence ratio, measured just one day after the freezing test, provides a good estimate of plant frost tolerance.Pinus halepensis / plant quality / stress tolerance / chilling hours / chlorophyll fluorescence / plant nutrition Résumé -Effets de la température sur la croissance et le développement de la résistance au stress de semis de Pin d'Alep (Pinus halepensis Mill.). Des semis de Pin d'Alep (Pinus halepensis), âgés d'un an, croissant sur un mélange de tourbe-vermiculite-écorce de pin dans des containers de 200 cm 3 , ont été mis en place dans une chambre de croissance et soumis, pour une période de 3 mois, à une température et photopériode décroissant progressivement. Des paramètres morphologiques, de nutrition et de teneur carbonée non structurale ont été mesurés. Des tests de potentiel de croissance racinaire, de résistance au froid et à la sécheresse ont été réalisés. Bien que la croissance en hauteur se soit arrêtée lorsque la température minimum eu atteint 9°C, la masse sèche des pousses continue d'augmenter. La concentration en potassium des aiguilles, le rapport K/N augmente progressivement et significativement au cours de l'essai. Ceci peut être attribué à une accumulation de potassium. Lorsque la croissance en hauteur s'est arrêtée, des changements physiologiques ont été constatés pour la concentration en azote et en sucre soluble des pousses, dans l'activité des racines et dans le maintien de la conductance hydraulique. Cependant, les tests de résistance au froid et à la sécheresse, de même que le potentiel de régénération racinaire, ne révélèrent aucun signe de tolérance de la plante au stress jusqu'à ce que la température minimum décroisse à 8°C et la ph...

Effects of ectomycorrhizal inoculation and the type of substrate on mycorrhization, growth and nutrition of containerised Pinus pinea L. seedlings produced in a commercial nursery

“…Survival and initial growth of out-planted seedlings under these unfavourable environmental conditions is highly dependent on their physiological quality after the nursery breeding period. Different biometrics (height, root collar diameter, shoot-root ratio) and physiological parameters (photosynthetic rates and nutrient accumulation in seedling tissues) have been used as indexes to determine the quality of seedlings produced in nursery [14,21].…”

Nursery fertilisation affects the frost-tolerance and plant quality of Eucalyptus globulus Labill. cuttings

“…For instance, Picea mariana needed at least 1.28% N in shoot tissues to ensure hardening, while, with 0.64% N, it did not harden and seedlings with 0.87% N showed a lesser degree of hardiness than those with 1.28% [3]. Besides, other factors such as K/N ratio [15] and P/N ratio [58] could be important in cold hardening and growth. If we examine the values of leaf N concentration in both ours and other related experiments [16], we can observe that plants with more than 1.25% N responded to the freezing test significantly better than those that had less than 1.0%.…”

“…Nevertheless, it still remains uncertain how fertilisation in nurseries influences plant quality and post-transplantation responses to low temperatures for most species [3], including E. globulus [16]. Changes to fertilisation schedules in late summer and autumn can be a part of this hardening process [15,28,32], by modifying quantities and proportions of the nutrients, particularly N, P and K. Therefore, it was hypothesised that N, P and K, supplied during the hardening stage in the nursery, affect plant quality and frosttolerance of Eucalyptus globulus Labill. To verify this hypothesis, morpho-physiological and growth parameters have been taken into account, as well as the field performance of plants one year after transplantation.…”

Effects of site preparation with micro-basins on Pinus halepensis Mill. afforestations in a semiarid ombroclimate

“…), coming near the studied area to avoid differences in the growth due to genetic characteristics of the individuals [13]. Site preparation consisted of banks 80 × 40 cm in surface and 40 cm in depth, dug with a pullshovel.…”

“…Fernández et al [13] indicate as well that environmental conditions affect survival and growth in forest plantations. On the other hand, Poret et al [20] point out that the highest rate of seedling mortality takes place during the first summer, and South et al [32] strengthen the positive influence exerted by the site preparation at the planting stage.…”