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The characteristic traits of maize (Zea mays L.) leaves affect light interception and photosynthesis. Measurement or estimation of individual leaf area has been described using discontinuous equations or bell-shaped functions. However, new maize hybrids show different canopy architecture, such as leaf angle in modern maize which is more upright and ear leaf and adjacent leaves which are longer than older hybrids. The original equations and their parameters, which have been used for older maize hybrids and grown at low plant densities, will not accurately represent modern hybrids. Therefore, the aim of this paper was to develop a new empirical equation that captures vertical leaf distribution. To characterize the vertical leaf profile, we conducted a field experiment in Jilin province, Northeast China from 2015 to 2018. Our new equation for the vertical distribution of leaf profile describes leaf length, width or leaf area as a function of leaf rank, using parameters for the maximum value for leaf length, width or area, the leaf rank at which the maximum value is obtained, and the width of the curve. It thus involves one parameter less than the previously used equations. By analysing the characteristics of this new equation, we identified four key leaf ranks (4, 8, 14 and 20) for which leaf parameter values need to be quantified in order to have a good estimation of leaf length, width and area. Together, the method of leaf area estimation proposed here adds versatility for use in modern maize hybrids and simplifies the field measurements by using the four key leaf ranks to estimate vertical leaf distribution in maize canopy instead of all leaf ranks.

Цель статьи – исследование особенностей морфометрических параметров и зольности листовой пластинки наиболее распространенных представителей древесных растений и зольности травянистых растений, произрастающих на территориях Гомельского региона с различным уровнем техногенного влияния, для выявления адаптационной стратегии растений в условиях техногенного воздействия. = The research purpose is the study of leaf plate morphometric parameters and ash-content features of the most widespread representatives of woody plants and grassy plants ash-content growing in Gomel Region territories with technogenic influence of various levels for plants adaptation strategy identification in the technogenic impact conditions.

The effect leaf .......morph.og....e.....................nesis and structure o..n....... .....leaf ..b......lades ...q.....ualit..y...w....as e..v.............aluated in su..mm.............er and autu..m.... nre.. growths of Festuca arundinacea Schreb. The experiment was conducted in 250 pots arranged in a completely randomised design (n=3) under natural climate conditions, without limitation of water, N and P. In each season swards were sampled 3 times (~300 tillers/replicate) to obtain leaves in 3 ontogenics stages of similar age (just expanded, adult and pre-senescence) corresponding to the 3 first sequentially appearing leaf generations. The leaf elongation rate (LER), leaf app earance interval (LAI), leaf life span (LLS), numb er of living leaves (NLL) and length of the leaf blade and sheath were measured in 5 marked tillers/replicate. In leaf blades, the NDF and the in vitro digestibility (NDFD and DMD) were determined (incubation at 24 h DaisyII digestor). The mo rphog enic variables were evaluated using repeated measures data analysis. Quality traits were analyzed by lineal function with age and leaf length. Comp arisons were made by dummy variable regressions and ANOVA (Tukey). The mean daily temp erature was low er in autumn than in summ er (13±4 vs. 21±3ºC). LER, LLS and LAI were low er (p<0.001) in autumn than in summ er but NLL was similar (p>0.23) in bo th season. Leaf length did not vary during autumn regrow th, but it was shorter than summ er (106±9 vs 239±98 mm ). Leaf blade length increased during summ er amo ng successive leaves of regrow th (~110 mm /generation) in relation (R²=93%) to the prog ressive in.. crease of the sheath tube length. Autumn leaf blades show ed low er NDF (39,8±0,8 vs 55,3±0,6%), higher NDFD (52,7±1,6 vs 46,8±1,1%) and DMD (69,3±0,9 vs 58,7±0,6%%) than that of summ er regrow th. It is concluded that summ er and autumn regrow ths differ in mo rphog enic, structure and quality variables, and that differences in DM digestibili, Se evaluó el efecto de la morfogénesis y estructura foliar en la calidad de las láminas de rebrotes de verano y otoño de Festuca arundinacea Schreb. Se utilizó un diseño completamente aleatorizado (n=3) en 250 macetas al aire libre sin limitantes hídricas de N y P. En los rebrotes de cada estación se realizaron tres cosechas de 300 macollos/repetición para obtener láminas en tres estados de desarrollo (recientemente expandida, adulta y pre-senescencia), correspondientes a tres generaciones consecutivas de hojas. En cinco macollos marcados por repetición se midió: la tasa de elongación foliar (TEF), el intervalo de aparición de hoja (IAH), la vida media foliar (VMF), el número de hojas vivas (NHV) y el largo de lámina y vaina. En las láminas se determinó el contenido de fibra detergente neutro (FDN), la digestibilidad de la FDN (DFDN) y la digestibilidad in vitro aparente de la materia seca (DAMS) (24 h de incubación, digestor DaisyII, ANKOM). Las variables de morfogénesis se evaluaron como medidas repetidas en el tiempo, y las de calidad ajustando funciones lineales con la edad y largo foliar. Las comparaciones se realizaron mediante análisis de variables Dummy y ANVA (Tukey). La temperatura media diaria del rebrote de otoño fue menor que en verano (13±4 vs. 21±3ºC). Los parámetros de morfogénesis TEF, VMF, IAH fueron menores (p<0,001) en otoño que en verano, pero el NHV no fue afectado (p>0,23). La longitud foliar en otoño no varió durante el rebrote y fue menor que en verano (106±10 vs 239±100 mm); que aumentó entre generaciones sucesivas (~110 mm/generación) en estrecha asociación (R²=93%) con el aumento progresivo de la longitud de vaina. Las láminas de otoño presentaron menor contenido de FDN (39,8±0,8 vs. 55,3±0,6%), mayor DFDN (52,7±1,6 vs. 46,8±1,1%) y DAMS (69,3±0,9 vs. 58,7±0,6%%) que las de verano. Se concluye que los rebrotes de verano y otoño difirieron en variables de morfogénesis, estructura y calidad. Asimismo, las diferencias en digestibilidad de la

The effect leaf .......morph.og....e.....................nesis and structure o..n....... .....leaf ..b......lades ...q.....ualit..y...w....as e..v.............aluated in su..mm.............er and autu..m.... nre.. growths of Festuca arundinacea Schreb. The experiment was conducted in 250 pots arranged in a completely randomised design (n=3) under natural climate conditions, without limitation of water, N and P. In each season swards were sampled 3 times (~300 tillers/replicate) to obtain leaves in 3 ontogenics stages of similar age (just expanded, adult and pre-senescence) corresponding to the 3 first sequentially appearing leaf generations. The leaf elongation rate (LER), leaf app earance interval (LAI), leaf life span (LLS), numb er of living leaves (NLL) and length of the leaf blade and sheath were measured in 5 marked tillers/replicate. In leaf blades, the NDF and the in vitro digestibility (NDFD and DMD) were determined (incubation at 24 h DaisyII digestor). The mo rphog enic variables were evaluated using repeated measures data analysis. Quality traits were analyzed by lineal function with age and leaf length. Comp arisons were made by dummy variable regressions and ANOVA (Tukey). The mean daily temp erature was low er in autumn than in summ er (13±4 vs. 21±3ºC). LER, LLS and LAI were low er (p<0.001) in autumn than in summ er but NLL was similar (p>0.23) in bo th season. Leaf length did not vary during autumn regrow th, but it was shorter than summ er (106±9 vs 239±98 mm ). Leaf blade length increased during summ er amo ng successive leaves of regrow th (~110 mm /generation) in relation (R²=93%) to the prog ressive in.. crease of the sheath tube length. Autumn leaf blades show ed low er NDF (39,8±0,8 vs 55,3±0,6%), higher NDFD (52,7±1,6 vs 46,8±1,1%) and DMD (69,3±0,9 vs 58,7±0,6%%) than that of summ er regrow th. It is concluded that summ er and autumn regrow ths differ in mo rphog enic, structure and quality variables, and that differences in DM digestibili, Se evaluó el efecto de la morfogénesis y estructura foliar en la calidad de las láminas de rebrotes de verano y otoño de Festuca arundinacea Schreb. Se utilizó un diseño completamente aleatorizado (n=3) en 250 macetas al aire libre sin limitantes hídricas de N y P. En los rebrotes de cada estación se realizaron tres cosechas de 300 macollos/repetición para obtener láminas en tres estados de desarrollo (recientemente expandida, adulta y pre-senescencia), correspondientes a tres generaciones consecutivas de hojas. En cinco macollos marcados por repetición se midió: la tasa de elongación foliar (TEF), el intervalo de aparición de hoja (IAH), la vida media foliar (VMF), el número de hojas vivas (NHV) y el largo de lámina y vaina. En las láminas se determinó el contenido de fibra detergente neutro (FDN), la digestibilidad de la FDN (DFDN) y la digestibilidad in vitro aparente de la materia seca (DAMS) (24 h de incubación, digestor DaisyII, ANKOM). Las variables de morfogénesis se evaluaron como medidas repetidas en el tiempo, y las de calidad ajustando funciones lineales con la edad y largo foliar. Las comparaciones se realizaron mediante análisis de variables Dummy y ANVA (Tukey). La temperatura media diaria del rebrote de otoño fue menor que en verano (13±4 vs. 21±3ºC). Los parámetros de morfogénesis TEF, VMF, IAH fueron menores (p<0,001) en otoño que en verano, pero el NHV no fue afectado (p>0,23). La longitud foliar en otoño no varió durante el rebrote y fue menor que en verano (106±10 vs 239±100 mm); que aumentó entre generaciones sucesivas (~110 mm/generación) en estrecha asociación (R²=93%) con el aumento progresivo de la longitud de vaina. Las láminas de otoño presentaron menor contenido de FDN (39,8±0,8 vs. 55,3±0,6%), mayor DFDN (52,7±1,6 vs. 46,8±1,1%) y DAMS (69,3±0,9 vs. 58,7±0,6%%) que las de verano. Se concluye que los rebrotes de verano y otoño difirieron en variables de morfogénesis, estructura y calidad. Asimismo, las diferencias en digestibilidad de la

Aimed to evaluate the morphogenetic and structural characteristics of the pasture of Brachiaria decumbens, subjected to several intensities and frequencies of cutting and nitrogen fertilization. Experimental design was randomized blocks in split plots, whit a 2 x 2 factorial arrangement relating to combinations of two cutting heights (40 and 50 cm) and two heights of residue (15 and 25 cm) at the plots and nitrogen fertilization (with or without nitrogen) in sub-plots, with four replications. Mophogenetic variables evaluated were: leaf elongation rate (LER), stem elongation rate (SER), leaf appearance rate (LAR), leaf senescence rate (LSR) and phyllochron; and structural features were: number of basal tillers (NBT), total number of leaves (TNL), number of leaves appeared (NLAp), number of dead leaves (NDL), number of alive leaves (NAL) and final leaf length (FLL). 100 kg N/ha allowed increase (p<0.10) on LER of 31.58% and 126.32% respectively for residues 15 and 25 cm. The NBT compared to cutting heights (40 to 50 cm) were affected (p<0.10) only with the use of nitrogen fertilizer, with average of 145.62 tillers/m 2 in 50 cm cut height. Residue height of 25 cm combined with cut height 40 cm increase leaf elongation rate and number of basal tillers, reducing expansion time, without changing other structural characteristics of the pasture., Objetivou-se avaliar as características morfogênicas e estruturais do pasto de Brachiaria decumbens, submetido a intensidades, fre- quências de corte e adubação nitrogenada. O delineamento experimental foi em blocos casualizados em esquema de parcelas subdividi- das, tendo na parcela o arranjo fatorial 2 x 2 referente a combinações entre duas alturas de corte (40 e 50 cm) e duas alturas de resíduo (15 e 25 cm) e nas sub-parcelas a adubação nitrogenada (com ou sem nitrogênio), com quatro repetições. As variáveis analisadas para as ca- racterísticas morfogênicas foram: taxa de alongamento foliar (TAlF); taxa de alongamento de colmo (TAlC); taxa de aparecimento foliar (TApF); taxa de senescência foliar (TSF) e filocrono; e para as características estruturais foram: número de perfilhos basais (NPB); número de folhas totais (NFT); número de folhas aparecidas (NFAp); nú- mero de folhas mortas (NFM); número de folhas vivas (NFV) e comprimento final da folha (CFF). A utilização de 100 kg/ha de N permitiu aumento (p<0,10) na TAlF de 31,58% e 126,32%, respec- tivamente para os resíduos de 15 e 25 cm. O NPB em comparação às alturas de corte (40 e 50 cm) foi afetado (p<0,10) apenas com a utilização da adubação nitrogenada, observando-se média de 145,62 perfilhos/m 2 para a altura de corte 50 cm. A altura de resíduo 25 cm combinada com a altura de corte 40 cm, junto à aplicação de 100 kg/ha de N, promovem maior produção de matéria seca total em menor espaço de tempo (28 dias), permitindo maiores taxas de lotação e facilitando o manejo no sistema de lotação rotacionada.

Aimed to evaluate the morphogenetic and structural characteristics of the pasture of Brachiaria decumbens, subjected to several intensities and frequencies of cutting and nitrogen fertilization. Experimental design was randomized blocks in split plots, whit a 2 x 2 factorial arrangement relating to combinations of two cutting heights (40 and 50 cm) and two heights of residue (15 and 25 cm) at the plots and nitrogen fertilization (with or without nitrogen) in sub-plots, with four replications. Mophogenetic variables evaluated were: leaf elongation rate (LER), stem elongation rate (SER), leaf appearance rate (LAR), leaf senescence rate (LSR) and phyllochron; and structural features were: number of basal tillers (NBT), total number of leaves (TNL), number of leaves appeared (NLAp), number of dead leaves (NDL), number of alive leaves (NAL) and final leaf length (FLL). 100 kg N/ha allowed increase (p<0.10) on LER of 31.58% and 126.32% respectively for residues 15 and 25 cm. The NBT compared to cutting heights (40 to 50 cm) were affected (p<0.10) only with the use of nitrogen fertilizer, with average of 145.62 tillers/m 2 in 50 cm cut height. Residue height of 25 cm combined with cut height 40 cm increase leaf elongation rate and number of basal tillers, reducing expansion time, without changing other structural characteristics of the pasture., Objetivou-se avaliar as características morfogênicas e estruturais do pasto de Brachiaria decumbens, submetido a intensidades, fre- quências de corte e adubação nitrogenada. O delineamento experimental foi em blocos casualizados em esquema de parcelas subdividi- das, tendo na parcela o arranjo fatorial 2 x 2 referente a combinações entre duas alturas de corte (40 e 50 cm) e duas alturas de resíduo (15 e 25 cm) e nas sub-parcelas a adubação nitrogenada (com ou sem nitrogênio), com quatro repetições. As variáveis analisadas para as ca- racterísticas morfogênicas foram: taxa de alongamento foliar (TAlF); taxa de alongamento de colmo (TAlC); taxa de aparecimento foliar (TApF); taxa de senescência foliar (TSF) e filocrono; e para as características estruturais foram: número de perfilhos basais (NPB); número de folhas totais (NFT); número de folhas aparecidas (NFAp); nú- mero de folhas mortas (NFM); número de folhas vivas (NFV) e comprimento final da folha (CFF). A utilização de 100 kg/ha de N permitiu aumento (p<0,10) na TAlF de 31,58% e 126,32%, respec- tivamente para os resíduos de 15 e 25 cm. O NPB em comparação às alturas de corte (40 e 50 cm) foi afetado (p<0,10) apenas com a utilização da adubação nitrogenada, observando-se média de 145,62 perfilhos/m 2 para a altura de corte 50 cm. A altura de resíduo 25 cm combinada com a altura de corte 40 cm, junto à aplicação de 100 kg/ha de N, promovem maior produção de matéria seca total em menor espaço de tempo (28 dias), permitindo maiores taxas de lotação e facilitando o manejo no sistema de lotação rotacionada.

S.L Torri , C. Descalzi, and E. Frusso. 2009. Estimation of leaf area in pecan cultivars (Carya illinoinensis). Cien. Inv. Agr. 36(1): 53-58. Nondestructive and mathematical approaches of modeling can be very convenient and useful for plant growth estimation. The objective of this research was to develop a simple, accurate and nondestructive predictive model for leaf area (LA) estimation in different pecan cultivars (Carya illinoinensis) commonly found in Argentina. Linear and exponential regression equations were fitted and evaluated for pecan cultivars 'Desirable', 'Harry Super', 'Kernodle', 'Mahan', 'Mahan-Stuart', 'Shoshoni', 'Stuart' and 'Success' (grafted on seedling pecan rootstocks, 24 years old, planted at 15 x 15 m) using length (L) and width (W) alternatively or both L and W in a stepwise analysis as non-forced independent variables. Stepwise regression analysis using L and W variables for each cultivar fitted the data better than L or W alone. A general equation for all cultivars showed high accuracy (R² = 0.93, p<0.0001). However, for certain cultivars, the general equation provided lower precision than the model for each cultivar. Therefore, we conclude that LA can be estimated through the general or individual model for each cultivar., El conocimiento del area foliar (AF) es esencial para evaluar el crecimiento vegetal y estimar el potencial productivo de los cultivos. El objetivo de este trabajo fue desarrollar un modelo predictivo simple, preciso, no destructivo y rápido, para estimar el AF de distintos cultivares de pecan (Carya illinoinensis) en plena producción en Argentina basado en el largo (L) y ancho (A) de los folíolos. Se estudiaron ocho cultivares 'Desirable' 'Harry Super', 'Kernodle', 'Mahan', 'Mahan-Stuart' 'Shoshoni', 'Stuart' y 'Success', injertados sobre un patrón franco de pecan, de 24 años de edad, plantados a 15 x 15 m. Se obtuvo una significativa correlación entre el L o A y el AF de los folíolos. Las mejores correlaciones para cada cultivar se obtuvieron a partir de un análisis discriminante, considerando como variables independientes no forzadas el L y A de cada foliólo. Se propone una ecuación general para el cálculo del AF de todos los cultivares. Sin embargo, para ciertos cultivares la ecuación general permitió un menor ajuste que la presentada para el respectivo cultivar. Se concluye que, según la precisión deseada, puede adoptarse la ecuación general para todos los cultivares o la ecuación particular para cada cultivar.

S.L Torri , C. Descalzi, and E. Frusso. 2009. Estimation of leaf area in pecan cultivars (Carya illinoinensis). Cien. Inv. Agr. 36(1): 53-58. Nondestructive and mathematical approaches of modeling can be very convenient and useful for plant growth estimation. The objective of this research was to develop a simple, accurate and nondestructive predictive model for leaf area (LA) estimation in different pecan cultivars (Carya illinoinensis) commonly found in Argentina. Linear and exponential regression equations were fitted and evaluated for pecan cultivars 'Desirable', 'Harry Super', 'Kernodle', 'Mahan', 'Mahan-Stuart', 'Shoshoni', 'Stuart' and 'Success' (grafted on seedling pecan rootstocks, 24 years old, planted at 15 x 15 m) using length (L) and width (W) alternatively or both L and W in a stepwise analysis as non-forced independent variables. Stepwise regression analysis using L and W variables for each cultivar fitted the data better than L or W alone. A general equation for all cultivars showed high accuracy (R² = 0.93, p<0.0001). However, for certain cultivars, the general equation provided lower precision than the model for each cultivar. Therefore, we conclude that LA can be estimated through the general or individual model for each cultivar., El conocimiento del area foliar (AF) es esencial para evaluar el crecimiento vegetal y estimar el potencial productivo de los cultivos. El objetivo de este trabajo fue desarrollar un modelo predictivo simple, preciso, no destructivo y rápido, para estimar el AF de distintos cultivares de pecan (Carya illinoinensis) en plena producción en Argentina basado en el largo (L) y ancho (A) de los folíolos. Se estudiaron ocho cultivares 'Desirable' 'Harry Super', 'Kernodle', 'Mahan', 'Mahan-Stuart' 'Shoshoni', 'Stuart' y 'Success', injertados sobre un patrón franco de pecan, de 24 años de edad, plantados a 15 x 15 m. Se obtuvo una significativa correlación entre el L o A y el AF de los folíolos. Las mejores correlaciones para cada cultivar se obtuvieron a partir de un análisis discriminante, considerando como variables independientes no forzadas el L y A de cada foliólo. Se propone una ecuación general para el cálculo del AF de todos los cultivares. Sin embargo, para ciertos cultivares la ecuación general permitió un menor ajuste que la presentada para el respectivo cultivar. Se concluye que, según la precisión deseada, puede adoptarse la ecuación general para todos los cultivares o la ecuación particular para cada cultivar.

English: Notwithstanding the emphasis of research on the intensification of sole-crop systems, the practice of inter-cropping remains widespread. Evidence is accumulating that indicates that under many situations it may represent a more efficient use of natural resources. Much of the basic information on the response of leaf growth to a single environmental factor was obtained during the 1960s when controlled environment facilities became available, yet it proved difficult to extrapolate results obtained in a controlled environment to the field situation. From this background emerged the notion that temperature constitutes one of the main environmental factors influencing leaf growth at the field level for both monocotyledonous and dicotyledonous crops. Sole- and inter-crop maize (Zea mays L.) and dry beans (Phaseolus vulgaris L.) were grown in order to examine the mechanisms by which temperature influences leaf growth during the early growth stage using of three consecutive planting dates in summer. For daily measurements of leaf growth 15 individual plant samples were measured from each replicated plot. Temperature variations were observed during the three planting dates, namely in November, January and March, from the automatic weather station at the experimental site. Generally the temperature increased gradually from the first planting in November until late January during the second planting and thereafter decreased from the beginning of February to reach the lowest temperature in May. Due to the difference in temperature at the consecutive planting dates the seedling emergence in the third planting showed took longer. From daily leaf length measurements of sole and inter-crop maize the leaf length proved to be almost linear with time (days after planting). During the first planting, the leaf growth was more rapid and the largest leaf size was recorded. In the case of the third planting it took a longer time to reach the same length due to low temperatures, wh, Afrikaans: Ongeag die klem wat navorsing op die verskerping van enkelbou-stelsels plaas, bly die beoefening van interbou-stelsels baie algemeen. Toenemende getuienis dui daarop dat dit sigself in vele toepasslnqs tot 'n doeltreffender benutting van natuurlike hulpbronne mag leen. Baie van die basiese inligting oor die reaksie van blaargroei op 'n enkele omgewingsfaktor is gedurende die 1960's ingewin toe beheerde omgewingsgeriewe beskikbaar geword het: tog het dit moelik geblyk te wees om uitslae wat in 'n beheerde omgewing verkry is, tot die veldsituasie uit te brei. Vanuit hierdie agtergrond het die denke ontstaan dat temperatuur een van die hoof omgewingsfaktore is wat blaargroei in die veld, beide op monocotyledoneuse en dicotyledoneuse gewasse, beinvloed. Enkel- en tussenverboude mielies (Zea mays L.) sowel as bone (Phaseolus vulgris L.) is gekweek met die doelom die meganismes waardeur temperatuur blaargroei beinvloed te ondersoek tydens hul vroeë groeistadium gedurende drie opeenvolgende planttye in die somer. Vyftien individuel plante is daagliks op drie ewebeeldige persele vir blaargroei gemeet. Temperatuurwisselings is tydens die drie plantdatums deur die nabygeleë outomatiese weerstasie aangeteken en wel in November, Januarie en Maart. Oor die algemeen het die temperatuur geleidelik toegeneem vanaf die eerste planting in November tot laat Januarie van die tweede planting en daarna gedaal van die begin van Februarie tot sy laagste vlak in Mei. Vanweë die temperatuurverskille vir die opeenvolgende plantdatums het die saadopkoms oor die derde planting langer gevat. Daaglikse bepalings van blaarlengte van enkel- en tussenverboude mielies het feitlik 'n reglynige verband met tyd (dae na planting) getoon. Gedurende die eerste planting was die blaargroei vinnig en is die grootste blaargrootte aangeteken. In die geval van die derde planting het bereiking van dieselfde grootte langer geneem weens lae temperature, terwyl hittespanning in die tweede planting stadige, Government of Eritrea

English: In South Africa nearly 47062 ha of wheat has been damaged by frost over the last ten years. This led to an average loss of income close to R 6.7 million annually. The objective of this study was to screen South African wheat cultivars for tolerance to freezing, to study the genetic variability for tolerance to freezing and to study the use of HMW-proteins to screen for tolerance to freezing. An artificial freezing test was used to screen 24 South African wheat cultivars for tolerance to freezing. Tolerance to freezing was obtained by calculating the percentage survival, root length and leaf length at -6 and -12°C. Norstar displayed superior tolerance to freezing at -6 and -12°C. Norstar, Scheepers 69, Belinda, Kavkaz, Molen, Carolus, Jager and PAN 3232 exhibited a high level of tolerance to freezing. The leaves of Caledon, PAN 3232, SST 966, SST 936, Norstar, Tugela DN and PAN 3235 showed a high level of tolerance to freezing. The roots of Kavkaz, Norstar, PAN 3235, Belinda, Jager, Carolus, PAN 3232, Betta and Molen exhibited a high level of tolerance to freezing. A full 6X6 diallel cross was used to determine the genetic variability, combining ability and inheritance of tolerance to freezing. Norstar, Tugela DN, PAN 3349, Karee, SST 66 and Snack were used as parents. Griffing's Model1, Method 1 was used for the analysis. Significant differences in tolerance to freezing were displayed by the F1- hybrids. Crosses such as SnacklNorstar, PAN 3349/Snack and Snack/fugela DN had a low level of tolerance to freezing. Karee/Norstar, SST 66/PAN 3349, Karee/PAN 3349 and SST 66/Norstar were nearly as freezing tolerant as Norstar. The lack of significant differences in the freezing tolerance between reciprocal crosses indicated that freezing tolerance was not affected by cytoplasmic effects. Norstar and Karee had the highest general combining ability. The high GCA:SCA ratio for percentage survival at -12°C and percentage reduction in survival, confirmed the additive ge, Afrikaans: In Suid Afrika is daar oor die laaste tien jaar sowat 47062 ha koring beskadig deur koue, wat gelei het tot enjaarlikse verlies aan inkomste van sowat R6.7 miljoen. Die doel van hierdie studie was om die vriestoleransie van Suid Afrikaanse koringcultivars te toets, om die genetiese variasie ten opsigte van vriestoleransie te bestudeer en om hoë molekulêre gewig proteïne (HMG-proteïne) te gebruik as aanduiding van vriestoleransie. en Kunsmatige vriestoets is gebruik om die vriestoleransie van 24 Suid Afrikaanse koringcultivars te toets. Die vriestoleransie is bepaal deur die persentasie oorlewing, blaarlengtes en wortellengtes by -6 en -12°C. Norstar het die hoogste vlak van vriestoleransie by -6 en -12°C gehad. Scheepers 69, Belinda, Kavkaz, Molen, Carolus, Jager en PAN 3232 het ook hoë vlakke van vriestoleransie getoon. Die blare van Caledon, PAN 3232, SST 966, SST 936, Norstar, Tugela DN en PAN 3235 het die hoogste vlakke van vriestoleransie getoon. Die wortels van Kavkaz, Norstar, PAN 3235, Belinda, Jager, Carolus, PAN 3232, Betta en Molen het die hoogste vlakke van vriestoleransie getoon. In 6X6 dialeel is gebruik on die genetiese variasie, kombineervermoë en oorerflikheid van vriestoleransie te bepaal. Norstar, Tugela DN, PAN 3349, Karee, SST 66 en Snack is gebruik as kruisingsouers. Betekenisvolle verskille is gevind tussen die F1-basters vir oorlewing, blaarlengte en wortellengte. SnacklNorstar, PAN 3349/Snack en Snack/Tugela DN het In lae vlak van vriestoleransie getoon. Karee/Norstar, SST 66/PAN 3349, Karee/PAN 3349 en SST 66/Norstar was amper net so vriestolerant soos Norstar. Geen betekenisvolle verskille tussen kruisings en hulle resiproke is waargeneem nie, dit bevestig dat daar geen sitoplasmiese invloede betrokke was by vriestoleransie nie. Norstar en Karee het die beste algemene kombineervermoë gehad. Die hoë verhouding van algemene kombineervermoë tot spesifieke kombineervermoë bevestig die additiewe geen aksie van vriestoleransie. Die ho, PANNAR Board of Directors

Marine ecosystems are under increasing human pressure and therefore in need of effective management. Marine protected areas (MPAs) can reduce the effects of local disturbances on habitat-forming benthic organisms like corals and seagrasses and are well-known to affect species composition. However, we know considerably less about their effects on organisms’ traits (physiological, morphological, and/or behavioural characteristics), which in turn dictate how organisms respond to stressors and influence ecosystem processes and services. We conducted a field survey along the Kenyan coast to assess the effects of MPAs on species and trait composition of seagrass assemblages; an important group of habitat-forming plants in shallow coastal areas that form the basis for multiple ecosystem services. We measured five morphological traits (shoot density, leaf length and width, number of leaves per shoot, and above:below-ground biomass ratio) on multispecies seagrass assemblages within government MPAs, community MPAs, and fished areas in three habitat zones (shallow, mid-lagoon and, reef). Using causal modelling (path analysis) of multivariate data, we found that MPAs influence seagrass species composition and, indirectly, trait composition in mid-lagoon areas. Meanwhile, there were no MPA effects in the shallow intertidal (potentially because of impacts from MPA-related tourism), and weak effects in the reef zone, presumably due to competition from corals. Finally, most of the MPA effects on overall seagrass trait composition were explained by species turnover, rather than phenotypic plasticity. In conclusion, MPAs appear to be an effective conservation tool for seagrass assemblages by reducing local disturbances and favouring seagrass species with certain traits, primarily in mid-lagoon areas. However, the lack of MPA effect in intertidal areas highlights the need for management approaches that regulate human impacts across the whole tropical coastal zone.