In the semi-arid west, moisture is often the limiting factor in plant growth. High crop production is dependent upon rainfall and supplemental moisture supplied through irrigation. Plants for these areas, which are most efficient in use of water, other things being equal, would be more desirable.

A boa formação durante o período de estabelecimento do pasto é fundamental para a manutenção do dossel forrageiro, com perfilhos vigorosos e produtivos nos ciclos subsequentes, neste sentido, a adubação nitrogenada é fundamental, pois contribui diretamente para a síntese de tecidos e manutenção da produtividade. Diante do exposto, o objetivo foi avaliar o efeito do nitrogênio em capim-mombaça (Panicum maximum Jacq.) durante o período de estabelecimento. O experimento foi conduzido em Araguaína, TO, durante 45 dias, iniciado no 15º e encerrado no 60º dia pósgerminação. Foi realizado experimento no delineamento de blocos casualizados com quatro doses de N (0, 30, 60, 90 kg.ha-1), e quatro repetições. Para avaliação do efeito do nitrogênio na planta foi realizado estudo de índices de eficiência de utilização do nitrogênio, eficiência agronômica, fisiológica e nutricional. Para o segundo capítulo, foi instalado esquema em parcelas subdivididas no delineamento de blocos casualizados, com quatro repetições, sendo as doses de N (0, 30, 60 e 90 kg N.ha-1) a parcela e os períodos avaliados (T1- primeiro período do 16º ao 30º; T2- segundo período do 31º ao 45º e T3- terceiro período do 46º ao 60º dia pós germinação) a sub parcela; onde avaliou-se as características morfogênicas e estruturais do capimmombaça. Concluiu-se que a recuperação do N aplicado e a eficiência agronômica pelo capim Mombaça aumentou com o incremento das doses. Observou-se, para todos os índices influência das doses aplicadas. A dose de 90 kg de N.ha-1, com base nos índices estudados, é a mais indicada para o período de estabelecimento do capim- Mombaça. O incremento das doses de nitrogênio influenciou positivamente as taxas de aparecimento, alongamento foliar, densidade de perfilhos e no número de folhas vivas por perfilho. Durante o período de estabelecimento foi identificado características diferentes da planta ao longo dos períodos, com maior taxa de senescência foliar (TSF), taxa de alongamento de colmo (TAlC) e taxa de alongamento foliar (TAlF) no T3, quando comparado ao T2 e T1, já no T1 ocorre a maior taxa de aparecimento foliar (TApF). / Proper nitrogen levels for forage establishment period is crucial to maintaining sward, with vigorous and productive tillers in subsequent cycles, in this sense, the nitrogen fertilization is critical as it contributes directly to the synthesis of tissues and maintaining productivity. Given the above, the objective was to evaluate the effect of nitrogen in mombaça (Panicum maximum Jacq.) during the period of establishment. The experiment conducted in Araguaína, TO, for 45° days, starting on the 15° and on the 60° day after germination. Experiment was conducted in a randomized block design with four N rates (0, 30, 60, 90 kg há-1), and with four replications. To evaluate the effect of nitrogen in the plant was conducted study Nitrogen use efficiency indices, agronomic efficiency, physiological and nutritional. For the second chapter scheme was installed in split plot in a randomized block design with four replications, with N rates (0, 30, 60 and 90 N.ha-1 kg) the plot and the evaluation period (T1 first sentence of 16º to 30º; T2 second sentence of 31º to 45º and T3 third sentence of 46º to 60º days after germination) to sub plot; where we evaluated the morphogenetic and structural characteristics of mombaça grass. It concluded that the recovery of applied N and agronomic efficiency at Mombasa grass increased with increasing doses. It observed, for all indices influence of the applied dose. A level of 90 kg N.ha-1, based on the indices studied, it is the most suitable for the establishment period of Mombaça grass. The increase in nitrogen rates positively influenced the appearance fees, leaf elongation, tiller density and number of live leaves per tiller. During the establishment period was identified different characteristics of the plant over the period, with higher leaf senescence rate (TSF), stem elongation rate (SER) and leaf elongation rate (LER) in T3 when compared with T2 and T1, T1 is already on the higher leaf appearance rate (LAR).

Submitted by Maria Beatriz Vieira (mbeatriz.vieira@gmail.com) on 2017-01-05T13:23:40Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) dissertacao_flavio_roberto_lamanna.pdf: 2740486 bytes, checksum: a699b8e658edfb292090fa2ba1acde89 (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-01-09T12:53:17Z (GMT) No. of bitstreams: 2 dissertacao_flavio_roberto_lamanna.pdf: 2740486 bytes, checksum: a699b8e658edfb292090fa2ba1acde89 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-01-09T13:05:34Z (GMT) No. of bitstreams: 2 dissertacao_flavio_roberto_lamanna.pdf: 2740486 bytes, checksum: a699b8e658edfb292090fa2ba1acde89 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-01-09T13:19:48Z (GMT). No. of bitstreams: 2 dissertacao_flavio_roberto_lamanna.pdf: 2740486 bytes, checksum: a699b8e658edfb292090fa2ba1acde89 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2014-08-18 / Sem bolsa / O uso de nitrogênio via fertilização em soja é controverso. Vários autores defendem a sua não utilização pelo fato da fixação biológica do nitrogênio ser capaz de suprir esta demanda. Com o objetivo de analisar respostas de aplicação de nitrogênio via uréia em cobertura foi realizado um experimento com duas cultivares de soja da Nidera Sementes: a NS5858 e a NS7200 de ciclos superprecoce e precoce, respectivamente. Foram utilizadas cinco doses de nitrogênio (0, 15, 30, 45 e 60 kg.ha-1 de nitrogênio) aplicadas nas entrelinhas do ensaio no início do florescimento. Os atributos avaliados foram produtividade, altura de plantas, altura da inserção da primeira vagem, peso de mil sementes e avaliação dos teores de óleo e proteína das sementes. Os resultados permitiram concluir que: não houve diferença estatística para produtividade para ambas cultivares avaliadas; as doses crescentes de nitrogênio provocaram tendência de diminuição dos teores de óleo na cultivar NS 7200; as doses de nitrogênio não causaram diferença significativa para os atributos altura de planta, altura da inserção da primeira vagem, peso de mil sementes e teor de proteína nas sementes para ambas cultivares avaliadas e teor de óleo nas sementes apenas para a cultivar NS 5858. / The use of Nitrogen via fertilization on soybean is controversial. Several authors advocate the non-use by the fact of biological nitrogen fixation to be able to meet this demand. To analyze responses of nitrogen application via urea topdressing was conducted an experiment with two cultivars of soy Nidera Seeds: NS5858 and NS7200 of very early and early cycles, respectively. We used five nitrogen levels (0, 15, 30, 45 and 60 kg.ha-1 of nitrogen) applied between the lines of the essay at the beginning of flowering. The attributes evaluated were productivity, plant height, height of the first insertion pod, weight of thousand seeds and evaluation of oil and protein contents of seeds. The results showed that: there was no statistical difference in productivity for both cultivars; increasing doses of nitrogen caused a downward trend in oil content in the cultivar NS 7200; nitrogen rates used in this experiment did not cause a statistically significant difference for the attributes plant height, height of the first pod, thousand grain weight, protein content for both cultivars and oil content just for the NS 5858 cultivar.

Made available in DSpace on 2014-08-20T13:59:06Z (GMT). No. of bitstreams: 1 tese_milene_conceicao_lima.pdf: 1117046 bytes, checksum: 61412e1bba4614df5d623d5245902770 (MD5) Previous issue date: 2013-04-05 / Several abiotic factors can coordinate or alter metabolic processes of growth and development plants such light, temperature, water availability, climate, soil nutrition and inorganic compounds. The objective of this study was to evaluate performance of A. millefolium L. (yarrow) against abiotic factors. To achieve this objective were have conducted two experiments in which the first was observed antimicrobial activity in vitro and essential oil yield of yarrow grown with nitrogen levels (0, 75 and 150 kg urea ha-1) and subjected different levels of shading 0% (full light) and 70% (70% shading). The second experiment were observed growth characteristics, production photosynthetic pigments, antioxidant enzymes activity, concentrations hydrogen peroxide, malondialdehyde, ascorbate and deidroascorbato, antioxidant activity by method DPPH and secondary metabolites synthesis in yarrow cultivated under light conditions (full light and blue, red and black shade net) and subjected different collection periods (eight weeks shading, two and four weeks after shading). The results show that oil yield extracted from flowers was stimulated by medium nitrogen level and full light increased the oil yield extracted from leaves. The highest essential oil yield was observed in reproductive structures. Antimicrobial activity of oil was confirmed against microorganisms species. Yeast strains were inhibited by the lowest concentration. The dry mass of leaves and flowers was favored in plants grown under full light. The content of chlorophyll a and b were higher in plants cultivated under blue net, total chlorophyll content was lower in plants under full light and plants two weeks after shading was increase of chlorophyll a, b and total, equivalent did not shaded plants. Catalase activity increased plants acclimated to high light intensity and low light did not stimulate ascorbate peroxidase, but increased superoxide dismutase and content of hydrogen peroxide. Lipid peroxidation was reduced presence of the spectrum blue and red light and low light intensity generated by nets black and blue, reduced accumulation of ascorbate. Content of deidroascorbato increased acclimation process to sunlight and antioxidant activity was more pronounced extracts of flowers. Levels total phenols and flavonoids were stimulated by full light. Oil yield extracted from flowers was higher than leaves. Major metabolite oil extracted from leaves was farnesol and flowers were farnesol and chamazulene. Results for medicinal species A. millefolium L. indicated that light intensity, light quality, collection periods and nitrogen fertilization influence growth, photosynthetic pigments production, secondary metabolites and antioxidant response. / Diversos fatores abióticos podem coordenar ou alterar os processos metabólicos de crescimento e desenvolvimento em plantas como a luz, temperatura, disponibilidade hídrica, clima, nutrição do solo e compostos inorgânicos. O objetivo deste estudo foi avaliar o comportamento de A. millefolium L. (mil-folhas) frente aos fatores abióticos. Para atingir este objetivo foram realizados dois experimentos, na qual no primeiro foi verificada a atividade antimicrobiana in vitro e rendimento do óleo essencial de mil-folhas cultivada com concentrações de nitrogênio (0, 75 e 150 Kg ureia ha-1) e submetida a diferentes níveis de sombreamento 0% (luz plena) e 70% (sombreamento 70%). No segundo experimento foram avaliadas características de crescimento, produção de pigmentos fotossintéticos, atividade de enzimas antioxidantes, teores de peróxido de hidrogênio, malondialdeído, ascorbato e deidroascorbato, atividade antioxidante pelo método DPPH e síntese de metabólitos secundários em mil-folhas cultivada sob condições de luminosidade (luz plena e sombreamento com malha azul, vermelha e preta) e submetida a diferentes períodos de coleta (oito semanas de sombreamento, duas e quatro semanas após o sombreamento). Os principais resultados mostram que o rendimento do óleo extraído de flores foi estimulado pela concentração nitrogenada intermediária e o extraído de folhas foi favorecido pela luz plena, sendo maior nas estruturas reprodutivas. A atividade antimicrobiana do óleo foi confirmada frente aos microrganismos, sendo as cepas fúngicas inibidas pela menor concentração. A massa seca das folhas e flores foi favorecida nas plantas cultivadas com luz plena. Os teores de clorofila a e b foram maiores nas plantas cultivadas com a malha azul, o conteúdo de clorofila total foi menor nas plantas sob luz plena e em plantas com duas semanas após o sombreamento ocorreu um incremento de clorofila a, b e total, equivalendo-se às plantas não sombreadas. A atividade da catalase aumentou em plantas aclimatadas em alta intensidade de luz e a baixa luminosidade não estimulou a ascorbato peroxidase, mas incrementou a superóxido dismutase e o teor de peróxido de hidrogênio. A peroxidação lipídica foi reduzida na presença dos espectros de luz azul e vermelha e a baixa intensidade de luz, gerada pelas malhas preta e azul, reduziu o acúmulo de ascorbato. O conteúdo de deidroascorbato aumentou em processo de aclimatação à luz solar e a atividade antioxidante foi mais acentuada em extratos de flores. Os teores de fenois e flavonoides totais foram estimulados pela luz plena. O rendimento do óleo extraído de flores foi maior em relação ao de folhas. O metabólito majoritário do óleo extraído de folhas foi o farnesol e os extraídos de flores foram o farnesol e camazuleno. Os resultados encontrados para a espécie medicinal A. millefolium L. indicaram que a intensidade luminosa, qualidade de luz, períodos de coleta e fertilização nitrogenada influenciam no crescimento, produção de pigmentos fotossintéticos, de metabólitos secundários e resposta antioxidante.

Η διακυμαινόμενη ασυμμετρία των φύλλων, δηλαδή η τυχαία απόκλιση από τη συμμετρία, θεωρείται ένα μέτρο της καταπόνησης που υπέστησαν κατά την ανάπτυξή τους. Η ασυμμετρία υποδηλώνει αναπτυξιακή αστάθεια και έχει προταθεί ότι συσχετίζεται αρνητικά με την αρμοστικότητα (fitness). Εάν η φωτοσύνθεση αποτελεί έναν έμμεσο δείκτη της αρμοστικότητας, αναμένεται, ένα φύλλο με μειωμένη αρμοστικότητα να είναι και φωτοσυνθετικά υποδεέστερο. Προς επιβεβαίωση αυτού, στην παρούσα διατριβή εξετάστηκαν εκατοντάδες άθικτα φύλλα σε συνολικά 7 διαφορετικά είδη ως προς τη διακυμαινόμενη ασυμμετρία, καθώς και ως προς τη φωτοσυνθετική τους απόδοση (δείκτες PItotal & Fv/Fm). Ο δείκτης PItotal υπολογίζεται με βάση την κινητική ανάλυση των in vivo μεταβολών του φθορισμού της χλωροφύλλης και λαμβάνεται εύκολα και γρήγορα (εντός δευτερολέπτων). Ο δείκτης αυτός θεωρείται ανάλογος της φωτοσυνθετικής αφομοίωσης του CO2 και περιγράφει την απόδοση τόσο του φωτοσυστήματος Ι (PSI) όσο και του φωτοσυστήματος ΙΙ (PSII). Ο παραδοσιακός δείκτης Fv/Fm προκύπτει άμεσα από τις in vivo μετρήσεις φθορισμού της χλωροφύλλης και υποδεικνύει τη μέγιστη φωτοχημική ικανότητα του PSII. Δύο φυτικά είδη (Pistacia lentiscus, Olea europea) επέδειξαν θετική συσχέτιση μεταξύ διακυμαινόμενης ασυμμετρίας και φωτοσυνθετικής ικανότητας, αποτελέσμα αντίθετο από τις αρχικές προβλέψεις. Το μόνο φυτικό είδος που επιβεβαίωσε την αρχική υπόθεση ήταν το Ceratonia siliqua. Στα υπόλοιπα είδη (Arbutus unedo, Cercis siliquastrum, Platanus orientalis, Populus alba) δεν υπήρξε συσχέτιση μεταξύ των δύο παραμέτρων. Τα φυτικά είδη που εμφάνισαν μεγάλες τιμές διακυμαινόμενης ασυμμετρίας ήταν και αυτά στα οποία η ασυμμετρία συχετίστηκε θετικά με τη φωτοσύνθεση. Συμπεραίνεται, εμμέσως ότι η ισχυρή ένταση της καταπόνησης κατά τα πρώιμα στάδια της ανάπτυξης των φύλλων σε μερικά φυτά ενδεχομένως να οδηγεί σε πιο σφριγηλή φωτοσύνθεση κατά την ωριμότητά τους ή σε μεγαλύτερη ικανότητα αντοχής στην καταπόνηση. Αν το συμπέρασμα είναι αληθές, τότε μπορεί μεν η συμμετρία να είναι ομορφότερη, δεν είναι όμως και αποδοτικότερη. Σε γενικές γραμμές, και με βάση τη βιβλιογραφία, ο δείκτης διακυμαινόμενης ασυμμετρίας των φύλλων δεν φαίνεται από μόνος του να επιτυγχάνει αξιόπιστη εκτίμηση της αρμοστικότητας. Για αυτό τον λόγο η χρησιμοποίησή του πρέπει να γίνεται με ιδιαίτερη προσοχή και συνάμα θα πρέπει να συνδυάζεται με σειρά άλλων δεδομένων-δεικτών. Ένας ακόμη δείκτης περιβαλλοντικής καταπόνησης μπορεί να είναι η εποχική συσσώρευση ερυθρών χρωστικών (ανθοκυανινών) που παρατηρείται στα ώριμα φύλλα ορισμένων φυτικών ειδών. Έχει προταθεί ότι οι ανθοκυανίνες των φύλλων λειτουργούν ως «ομπρέλα» προστασίας για τη φωτοσυνθετική συσκευή ενάντια στη φωτοαναστολή. Ως προς την εξέταση αυτής της υπόθεσης, η παρούσα διατριβή χρησιμοποίησε δύο πειραματόφυτα που εμφανίζουν εποχική ερυθρότητα στα φύλλα ορισμένων ατόμων τους. Αυτά είναι το Pistacia lentiscus και το Cistus creticus. Αρχικά όσον αφορά το P. lentiscus, εξετάστηκε η συσχέτιση του βαθμού φωτοπροστασίας με τις πραγματικές συγκεντρώσεις ανθοκυανινών σε φύλλα ατόμων που φύονται σε συνθήκες πεδίου. Το συγκεκριμένο εγχείρημα αποτελεί καινοτομία, αφού μέχρι σήμερα δεν έχει μελετηθεί η φωτοπροστασία σε σχέση με τη διαβάθμιση της ερυθρότητας των φύλλων. Προς αυτή τη κατεύθυνση χρησιμοποιήθηκαν μη επεμβατικές οπτικές μέθοδοι (φάσματα ανακλαστικότητας και φθορισμός χλωροφύλλης) για να αποτιμήσουν τα επίπεδα ανθοκυανινών και χλωροφυλλών καθώς και τη φωτοχημική απόδοση του PS II, σε εκατοντάδες ώριμα φύλλα του φυτικού είδους P. lentiscus (σχίνος). Ο σχίνος κατά τη χειμερινή περίοδο εμφανίζει κόκκινους (όλων των διαβαθμίσεων ερυθρού χρώματος) και πράσινους φαινότυπους. Αντίθετα με την υπόθεση που υποστηρίζει το φωτοπροστατευτικό ρόλο των ανθοκυανινών, η ένταση της ερυθρότητας συσχετίστηκε θετικά με τη φωτοαναστολή και αρνητικά με τα επίπεδα των εμπεριεχόμενων χλωροφυλλών στα φύλλα. Έτσι, ο πιθανός φωτοπροστατευτικός ρόλος των ανθοκυανινών δεν επιβεβαιώθηκε. Ωστόσο, η χειμερινή ερυθρότητα των φύλλων στο σχίνο μπορεί να χρησιμοποιηθεί ως ένας ρεαλιστικός, γρήγορος και μη επεμβατικός τρόπος εντοπισμού ατόμων «ευάλωτων» στη χειμερινή καταπόνηση. Σε μετέπειτα στάδιο στο ίδιο φυτικό είδος, εξετάστηκε in situ η σχέση της χειμερινής ερυθρότητας των φύλλων με σειρά άλλων φωτοσυνθετικών παραμέτρων. Συγκρινόμενοι με τους πράσινους φαινότυπους κατά τη διάρκεια του χειμώνα, οι ερυθροί (ανθοκυανικοί) φαινότυποι παρουσίασαν χαμηλότερες ταχύτητες αφομοίωσης CO2. Βρέθηκε ότι αυτό οφείλεται στη χαμηλή περιεκτικότητα ή/και ενεργότητα του ενζύμου καρβοξυλάση/οξυγονάση της διφωσφορικής ριβουλόζης (Rubisco) των ερυθρών φύλλων, ενώ ταυτόχρονα η στοματική αγωγιμότητα δεν φάνηκε να είναι περιοριστική για τη φωτοσύνθεση. Συγχρόνως, οι ερυθροί φαινότυποι βρέθηκε ότι περιέχουν λιγότερο άζωτο σε σχέση με τους πράσινους. Το εύρημα αυτό πιθανώς συνδέεται με την παρατηρούμενη χαμηλή περιεκτικότητα του ενζύμου Rubisco και τον μειωμένο φωτοσυνθετικό ρυθμό των ερυθρών φύλλων. Η περιορισμένη ικανότητα των αντιδράσεων καρβοξυλίωσης να χρησιμοποιήσουν αναγωγική δύναμη και ηλεκτρόνια, ενδεχομένως εξηγεί και τη μειωμένη απόδοση παγίδευσης φωτονίων του PSII που σημειώνεται στους ερυθρούς φαινοτύπους. Σε οποιαδήποτε περίπτωση, η ανάπτυξη της ανθοκυανικής «ομπρέλας» δεν φαίνεται να αποσοβεί το κίνδυνο φωτοαναστολής της φωτοσύνθεσης στον ερυθρό φαινότυπο του σχίνου. Ως παραπροϊόν της εργασίας με το P. lentiscus, εξετάστηκε η πιθανή επίδραση των φυσικών διακυμάνσεων του αζώτου των φύλλων του στις φωτεινές αντιδράσεις της φωτοσύνθεσης. Συγκεκριμένα, εξετάστηκαν οι φυσιολογικές διακυμάνσεις του αζώτου ώριμων φύλλων σε συνδυασμό με την ανάλυση των αντίστοιχων καμπυλών ταχείας ανόδου του φθορισμού της χλωροφύλλης. Η μαθηματική ανάλυση των καμπυλών έγινε σύμφωνα με το λεγόμενο «JIP-test», γεγονός που επέτρεψε την εκτίμηση της εν δυνάμει δραστηριότητας των δύο φωτοσυστημάτων. Τα αποτελέσματα υπέδειξαν εξάρτηση από την εποχή, επιτρέποντας την εξαγωγή του συμπεράσματος ότι η έλλειψη αζώτου επηρεάζει επιλεκτικά και αρνητικά το PSI, ενώ η αρνητική επίδραση στο PSII περιορίζεται μόνο κατά τη δυσμενή-χειμερινή περίοδο του έτους. Ένας δεύτερος Μεσογειακός θάμνος που εξετάστηκε ήταν το είδος Cistus creticus. Όπως και ο σχίνος, το είδος αυτό επιδεικνύει χαρακτηριστική ενδοειδική ποικιλομορφία στην έκφραση του ανθοκυανικού χαρακτήρα στα φύλλα του. Συγκεκριμένα, μερικά άτομα κοκκινίζουν το χειμώνα, ενώ γειτονικά τους κάτω από τις ίδιες περιβαλλοντικές συνθήκες παραμένουν πράσινα. Η ερυθρότητα των φύλλων διατηρείται μέχρι τα μέσα της άνοιξης. Αυτό το σύστημα απεδείχθη κατάλληλο, όχι μόνο για τη μελέτη του φυσιολογικού ρόλου των ανθοκυανινών αλλά και για τη προσέγγιση οικολογικών ερωτημάτων που σχετίζονται με την αρμοστικότητα (fitness) των δύο φαινότυπων. Επίσης, απεδείχθη πως η φυλλική ερυθρότητα μπορεί να χρησιμοποιηθεί ως ένας οπτικός δείκτης καταπόνησης. Ως τελικές παράμετροι αρμοστικότητας χρησιμοποιήθηκαν, η αναπαραγωγική προσπάθεια ως ο αριθμός ανθέων ανά άτομο, η αναπαραγωγική επιτυχία ως ο αριθμός σπερμάτων ανά άτομο καθώς και η επικονιστική επιτυχία ως ο αριθμός καρπών ανά αριθμό ανθέων και ως ο αριθμός σπερμάτων ανά καρπό. Η μελέτη αυτή, συνδιαζόμενη με σειρά φυσιολογικών δεικτών που εξέτασαν άλλα μέλη της ερευνητικής ομάδας του εργαστηρίου μας έδειξαν ότι, παρόλο που οι φυσιολογικοί δείκτες εμφανίζουν τον ερυθρό φαινότυπο υποδεέστερο, αντίθετα οι αναπαραγωγικοί δείκτες (αποτελέσματα παρούσας διατριβής) δεν παρουσίασαν διαφορές. Εν τέλει, μπορεί ίσως να λεχθεί πως η παρουσία της ερυθρότητας υποδεικνύει μεν «ασθενέστερα» άτομα (που με τη βοήθεια των ανθοκυανινών ίσως επιτυγχάνουν κάποια αντιστάθμιση αυτών των ενδογενών φυσιολογικών και γενετικών αδυναμιών τους), όχι όμως τόσο ασθενικά ώστε να επηρεάζεται αρνητικά η αναπαραγωγική τους επιτυχία και αρμοστικότητα. / Fluctuating asymmetry, small nondirectional deviations from perfect symmetry, has been proposed as a useful indicator of environmental stress. The developmental instability of an organism may induce asymmetric characters. Hence, a high degree of developmental instability, morphologically manifested as fluctuating asymmetry, may indicate less fitness. According to that, less fit individuals are expected to have asymmetric leaves and this may have a negative impact in their photosynthetic yield. In this investigation, fluctuating asymmetry and two photosynthetic indices (PItotal, Fv/Fm) has been measured in a great number of leaves in 7 plant species. PItotal, is an index which expresses the relative photosynthetic performance. It is calculated from the kinetics of fast chlorophyll a fluorescence rise curves according to the so-called «JIP-test». It is considered to be positively correlated to CO2 assimilation rates, hence to productivity based on photosynthesis. Fv/Fm, is a second photosynthetic index which indicates the maximum photosystem II (PSII) photochemical efficiency. Fluctuating asymmetry was positively correlated to both photosynthetic indices in two plant species (Pistacia lentiscus, Olea europea). These results do not support the initial hypothesis of this investigation. Contrary, the species Ceratonia siliqua shows a negative correlation between fluctuating asymmetry and the two photosynthetic indices. Furthermore, in four plant species (Arbutus unedo, Cercis siliquastrum, Platanus orientalis, Populus alba), fluctuating asymmetry and photosynthetic performance were not correlated. It happened that the two species deviating from the initial hypothesis (P. lentiscus and O. europea) display the maximum mean fluctuating asymmetry values among all species included in this investigation. In conclusion, it seems that in some plants whose leaves have experienced high stress as young are more photosynthetically potent as mature. Moreover, these results suggest that the relation between fluctuating asymmetry and photosynthesis is species-specific. Finally, the results show that fluctuating asymmetry may not be a reliable index of developmental instability and stress exposure in plants. Leaf anthocyanins are believed to afford protection against photoinhibition, yet the dependence of protection on actual anthocyanin concentrations has not been investigated. To that aim, non-invasive optical methods (spectral reflectance and chlorophyll fluorescence) were used to assess levels of anthocyanins and chlorophylls as well as photosystem II (PSII) photochemical efficiency in hundreds of leaves from the mastic tree (Pistacia lentiscus). This species displays a continuum of leaf tints during winter from fully green to fully red under field conditions. Contrary to expectations based on the photoprotective hypothesis, the strength of leaf redness was positively correlated to the extent of mid-winter chronic photoinhibition and negatively correlated to leaf chlorophyll contents. Hence, a photoprotective role for anthocyanins is not substantiated. Instead, we argue that winter leaf redness may be used reliably, quickly and non-invasively to locate vulnerable individuals in the field. Given that winter-red leaf phenotypes in the mastic tree are more vulnerable to chronic photoinhibition during the cold season, we asked whether corresponding limitations in leaf gas exchange and carboxylation reactions could also be manifested. During the cold («red») season, net CO2 assimilation rates (A) and stomatal conductances (gs) in the red phenotype were considerably lower than the green phenotype, while leaf internal CO2 concentration (Ci) was higher. The differences were abolished in the «green» period of the year, the dry summer included. Analysis of A versus Ci curves indicated that CO2 assimilation during winter in the red phenotype was limited by Rubisco content and/or activity rather than stomatal conductance. Concomitant to that, leaf nitrogen levels in the red phenotype were considerably lower during the red-leaf period. Hence, we suggest that the inherently low leaf nitrogen levels are linked to the low net photosynthetic rates of the red plants through a decrease in Rubisco content. Accordingly, the reduced capacity of the carboxylation reactions to act as photosynthetic electron sinks may explain the corresponding loss of PSII photon trapping efficiency, which cannot be fully alleviated by the screening effect of the accumulated anthocyanins. In a next step we examined whether leaf nitrogen level affects photosynthetic light reactions. Although it is amply documented that CO2 assimilation rates are positively correlated to leaf nitrogen, corresponding studies on a link between this nutrient and photosynthetic light reactions are scarce, especially under natural field conditions. In this final investigation with mastic tree, we exploited natural variation in nitrogen content of mature leaves of P. lentiscus in conjunction with fast chlorophyll a fluorescence rise (the OJIP curves) analysed according to the so-called «JIP-test», as this was recently modified to allow also for the assessment of events in or around photosystem I (PSI). The results depended on the sampling season, with low nitrogen leaves displaying lower efficiencies for electron flow from intermediate carriers to final PSI acceptors and lower relative pool sizes of these acceptors, both during the autumn and winter. However, parameters related to the PSII activity (i.e. quantum yields for photon trapping and electron flow along PSII, efficiency of a trapped exciton to move an electron from QA- to intermediate carriers) were limited by low nitrogen only during the winter period. As a result, parameters like the quantum yield of total electron flow along both photosystems as well as the total photosynthetic performance index (PItotal) were positively correlated to leaf nitrogen independently of season. We conclude that nitrogen deficiency under field conditions preferentially affects PSI activity while the effects on PSII are evident only during the stressful period of the year. In the last part of this dissertation we asked whether the leaf anthocyanic trait confers long term benefits to the plant and to that aim parameters directly related to fitness, i.e. reproductive effort and success as well as seed germinability were registered in winter-red and green phenotypes of Cistus creticus growing in the field under apparently similar conditions. The results indicated that both phenotypes displayed similar flower numbers, pollination success and seed yield, mass and germinability. As judged by the similar final reproductive output, vulnerability to the winter stress does not render the red phenotype less fit, nor anthocyanin accumulation render it more fit. Although an apparent compensating function for anthocyanins may be inferred, it can not be linked to a protection against photoinhibition of photosynthesis. Moreover, the photosynthetic inferiority of the red phenotype although linked to slightly reduced leaf number, (results from other members of our laboratory) it was not limiting for reproductive effort and success. Regardless of function, winter leaf redness may indicate photosynthetically weak, yet not necessarily less fit individuals in C. creticus.