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In this work we present evidence that the drought stress syndrome in the flag leaves and ears of wheat plants, provoked by the production of ethylene (shortening the grain filling period and lowering the grain weight) is reversed by the application of a free radical scavenger, sodium benzoate or the ethylene synthesis inhibitor, aminoethoxyvinylglycine. Rehydration by watering also attenuated the detrimental effect of the water deficit. Consequently, the grain filling period was longer, the grain weight increased, and the total protein content was higher than that in plants watered regularly.

This work was aimed at testing the involvement of ethylene in the maturation of grain and senescence of the foliar structures of the wheat inflorescence . Whole wheat ears emitted ethylene to the atmosphere . From pre-anthesis, ethylene emission progressively increased from 0.76 nl g -1 FW h -1 to a peak 1 .53 nl g -1 FW h -1 at the hard dough stage of the grains, to fall to a minimum of 0 .10 nl g -1 FW h -1 at the dormant seed stage . Ethephon increased the ethylene release, hastened the process of grain maturation and senescence of the ears . Aminoethoxyvinylglycine and silver thiosulfate produced the opposite effects . It is concluded that ethylene plays a role in grain maturation and in the senescence of the green bracts of the inflorescence .Abbreviations : Ag+ = silver ion ; AVG = aminoethoxyvinylglycine ; SAM = S-adenosylmethionine ; STS = silver thiosulfate ; TGW = thousand grain weight 107

The main objective of the present work was to examine the effects of the red:far‐red ratio (R:FR) prevailing during leaf development on the photosynthetic capacity of mature leaves. Plants of Phaseolus vulgaris L. cv. Balin de Albenga were grown from time of emergence in a controlled environment room, 25 ± 3°C, 12‐h photoperiod, with different light treatments:a) high photosynthetic photon flux density (PPFD) = 800 μmol m−1 s−1+ high R:FR= 1.3;b) low PPFD= 300 μmol m−2 s−1+ high R:FR= 1.3; c) high PPFD=800 μmol m−2 s−1+ low R:FR= 0.7; d) low PPFD= 300 μmol m−2s−1+ low R:FR=0.7. With an R:FR ratio of 1.3, a decrease in irradiance during leaf growth reduced photosynthesis when measured at moderate to high PPFD; but when measured at low PPFD, leaves expanded under low irradiance actually had photosynthesis rates higher than those of leaves grown in high irradiance. A low R:FR ratio during development reduced the photosynthetic capacity of the leaves. In leaves expanded under R:FR = 0.7 and high irradiance photosynthesis was reduced by 42 to 89%, depending on the PPFD at which measurements were made, whereas for leaves developed at R:FR = 0.7 and low irradiance photosynthesis decreased by 21 to 24%, compared to leaves under R:FR = 1.3 and similar irradiance. The reduced photosynthetic capacity under R:FR = 0.7 and high irradiance. In natural environments, leaves may experience low R:FR conditions temporarily during their development, and this may affect their future photosynthetic capacity in full sunlight.

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Treatment of flag leaves and ears of wheat plants with MJ (jasmonic acid methylester) (10 −5 and 10 −4 M) did not increase ethylene production, but it did accelerate senescence as indicated by the loss of chlorophyll. MJ also caused the closure of stomata, and consequently the rates of transpiration and photosynthesis decreased. Early maturity shortened the grain filling period, so the thousand grain weight was lower. Although ethylene elicited the same physiologic effects, the syndrome of senescence by MJ is independent of the former. We conclude that senescence and death in wheat are far from being elucidated; however, MJ and ethylene seem to participate in the phenomenon.

1992. Regulation of the photosynthetic capacity of primary bean leaves by the red:far-red ratio and photosynthetic photon flux density of incident light. -Physioi. Plant. 85: 97-101,The main objective of the present work was to examine the effects of the red:far-red ratio (R:FR) prevailing during leaf development on the photosynthetic capacity of mature leaves. Plants of Phaseotus vulgaris L. cv. Balin de Albenga were grown from time of emergence in a controlled environment room, 25 ± 3*C, 12-h photoperiod, with different light treatments: a) high photosynthetic photon flux density (PPFD) = 800nmolm-^s-' + high R:FR = 1.3; b) low PPFD = 300 [lmol m^^ s"^ + high R:FR = 1.3; c) high PPFD = 800 fimol m"^ s~' -t-low R:FR = 0,7; d) low PPFD = 300 |xmol m"-s ' + low R:FR = 0.7. With an R:FR ratio of 1.3, a decrease in irradiance during leaf growth reduced photosynthesis when measured at moderate to high PPFD; but when measured at low PPFD, leaves expanded under low irradiance actually had photosynthesis rates higher than those of leaves grown in high irradiance, A low R::FR ratio during development reduced the photosynthetic capacity of the leaves, ln leaves expanded under R:FR = 0,7 and high irradiance photosynthesis was reduced by 42 to 89%, depending on the PPFD at which measurements were made, whereas for leaves developed at R:FR = 0.7 and low irradiance photosynthesis decreased by 21 to 24%, compared to leaves under R:FR = 1.3 and similar irradiance. The reduced photosynthetie capacity under R:FR = 0.7 correlated with lower chlorophyll content on an area basis. As with photosynthesis, the decrease in chlorophyll was more pronounced in leaves under R:FR = 0.7 and high irradiance. In natural environments, leaves may experience low R:FR conditions temporarily during their development, and this may affect their future photosynthetic capacity in full sunlight.