Ontogenetic patterns of leaf CO2 exchange, morphology and chemistry in Betula pendula trees

Abstract

In order to explore ontogenetic variation in leaf-level physiological traits of Betula pendula trees, we measured changes in mass-(A mass ) and area-based (A area ) net photosynthesis under light-saturated conditions, mass-(RS mass ) and area-based (RS area ) leaf respiration, relative growth rate, leaf mass per area (LMA), total nonstructural carbohydrates (TNC), and macro-and micronutrient concentrations. Expanding leaves maintained high rates of A area , but due to high growth respiration rates, net CO 2 fixation occurred only at irradiances >200 µmol photons m -2 s -1 . We found that full structural leaf development is not a necessary prerequisite for maintaining positive CO 2 balance in young birch leaves. Maximum rates of A area were realized in late June and early July, whereas the highest values of A mass occurred in May and steadily declined thereafter. The maintenance respiration rate averaged ≈8 nmol CO 2 g -1 s -1 , whereas growth respiration varied between 0 and 65 nmol CO 2 g -1 s -1 . After reaching its lowest point in mid-June, leaf respiration increased gradually until the end of the growing season. Mass and area-based dark respiration were significantly positively correlated with LMA at stages of leaf maturity, and senescence. Concentrations of P and K decreased during leaf development and stabilized or increased during maturity, and concentrations of immobile elements such as Ca, Mn and B increased throughout the growing season. Identification of interrelations between leaf development, CO 2 exchange, TNC and leaf nutrients allowed us to define factors related to ontogenetic variation in leaf-level physiological traits and can be helpful in establishing periods appropriate for sampling birch leaves for diagnostic purposes such as assessment of plant and site productivity or effects of biotic or abiotic factors.

The influence of root-zone temperature on growth of Betula pendula Roth.

“…High starch concentration in the leaves may reflect that roots grown in hydroponic solution become a lower sink than roots grown in soil. However, we cannot exclude the possibility that the method used in the present study may have overestimated the starch concentration compared with the use of enzymes (compare Rey and Jarvis 1998 with Oleksyn et al 2000). On the other hand, the method we used has not overestimated starch concentration in Picea abies compared with the use of enzymes (compare Linder 1995with Dalen et al 2001.…”

A Study of Co2 Gas Exchange in Karelian Birch Under Low Solar Radiation Conditions in Plantations With Different Levels of Soil Fertility

“…Пластичность этих характеристик в значительной мере связана с содержанием азота в листьях и корнях [Reich et al, 1996]. В работе, где исследование CO 2 -газообмена у березы повислой проводилось на протя-жении вегетационного сезона, показано, что интенсивность дыхания листа быстро снижа-лась в течение первых шести недель развития листьев [Oleksyn et al, 2000]. За этот период времени рассчитанное на площадь дыхание, приведенное к 20 °С, снижалось примерно в 10 раз -от 2,7 до 0,3 мкмоль СО 2 ·м -2 ·с -1…”

Yaprak Senesensi: Fizyolojik ve Moleküler Düzenlenmesine Bakış

“…Senesens sırasında klorofil ve total çözünür proteinler bozulur ve proteolitik aktivite artar [20]. [21]. Pisum sativum L.'de karanlık tarafından teşvik edilen senesens sırasında mitokondrilerin ve yaprak peroksizomlarının sayısının arttığı rapor edilmiştir [22].…”

“…Ek olarak, peroksizomlarda dehidroaskorbat redüktaz (DHAR) aktivitesi artarken, askorbat peroksidaz (APX) ve monodehidroaskorbat redüktaz aktivitesi azalmaktadır [24]. Senesens sırasında peroksizomlardaki manganez-superoksit dismutaz (Mn-SOD) aktivitesi büyük ölçüde artarken, mitokondrilerdeki Mn-SOD aktivitesinin önemli ölçüde azaldığı gözlenmiştir [21]. Yapılan çalışmalarda, yaprak senesensi sırasında, miktarları artan yaklaşık 100 gen Arabidopsis, domates, mısır, tütün, patates, fasulye gibi çeşitli bitki türlerinden izole edilmiştir.…”