358
R.W. Pearcy and W.A. Plitsch
reproduction is possible, the 20 to 30% reduction in assimilation because of
the induction requirement is probably very significant to the ecology of this
species. Thus, minimization of induction could be advantageous. This
appears to have occurred in Adenocaulon through minimization of stomatal
limitations that allows for a relatively rapid induction response (Pfitsch
and Pearcy 1989b). However, the biochemical limitations are still present
and under some circumstances may be even greater in Adenocaulon than
observed in other species.
Both the daily and seasonal estimates of the contribution of sunflecks
show the extreme heterogeniety in this resource in the understory. While a
good picture of the effects of the temporal heterogeniety of sun flecks on
photosynthesis has been developed, much less is known about the spatial
heterogeniety and its role in the ecology of these plants. In particular,
there needs to be more work on the constraints on sunfleck utilization and
also on the interactions between diffuse and direct light in terms of resource
allocation.
Acknowledgments. This research was supported by NSF Grants BSR 86-00065 and BSR
88-17820
References
Bjorkman 0, Ludlow M (1972) Characterization of the light climate of a Queensland
rainforest. Carnegies Inst Wash Yearb 71: 85-94
Bjorkman 0, Ludlow M, Morrow P (1972) Photosynthetic performance of two rainforest
species in their native habitat and analysis of their gas exchange. Carnegie Inst Wash
Yearb 71: 94-102
Chazdon RL (1988) Sunflecks and their importance to forest understory plants. Adv Ecol
Res 18: 1-63
Chazdon RL, Fetcher N (1984) Photosynthetic light environments in a lowland tropical
forest in Costa Rica. J Ecol 72: 553-564
Chazdon RL, Pearcy RW (1986a) Photosynthetic responses to light variation in rain forest
species. I. Induction under constant and fluctuating light conditions. Oecologia 69:
517-523
Chazdon RL, Pearcy RW (1986b) Photosynthetic responses to light variation in rain
forest species. II. Carbon gain and light utilization during lightflecks. Oecologia 69:
524-531
Farquhar GD, Richards RA (1984) Isotopic composition of plant carbon correlates with
water use efficiency of wheat genotypes. Aust J Plant Physioll1: 539-552
Farquhar GD, O'Leary MH, Berry JA (1982) On the relationship between carbon isotope
discrimination and intercellular carbon dioxide concentration in leaves. Aust J Plant
Physiol 9: 121-137
Kirschbaum MUF, Pearcy RW (1988) Gas exchange analysis of the relative importance of
stomatal and biochemical factors in photosynthetic induction in Alocasia macrorrhiza.
Plant Physiol 86: 782- 785
Miller E, Norman JM (1971) A sunfleck theory for plant canopies. II. Penumbra effect:
intensity distributions along sunfleck segments. Agron J 63: 739-748
R.W. Pearcy and W.A. Plitsch
reproduction is possible, the 20 to 30% reduction in assimilation because of
the induction requirement is probably very significant to the ecology of this
species. Thus, minimization of induction could be advantageous. This
appears to have occurred in Adenocaulon through minimization of stomatal
limitations that allows for a relatively rapid induction response (Pfitsch
and Pearcy 1989b). However, the biochemical limitations are still present
and under some circumstances may be even greater in Adenocaulon than
observed in other species.
Both the daily and seasonal estimates of the contribution of sunflecks
show the extreme heterogeniety in this resource in the understory. While a
good picture of the effects of the temporal heterogeniety of sun flecks on
photosynthesis has been developed, much less is known about the spatial
heterogeniety and its role in the ecology of these plants. In particular,
there needs to be more work on the constraints on sunfleck utilization and
also on the interactions between diffuse and direct light in terms of resource
allocation.
Acknowledgments. This research was supported by NSF Grants BSR 86-00065 and BSR
88-17820
References
Bjorkman 0, Ludlow M (1972) Characterization of the light climate of a Queensland
rainforest. Carnegies Inst Wash Yearb 71: 85-94
Bjorkman 0, Ludlow M, Morrow P (1972) Photosynthetic performance of two rainforest
species in their native habitat and analysis of their gas exchange. Carnegie Inst Wash
Yearb 71: 94-102
Chazdon RL (1988) Sunflecks and their importance to forest understory plants. Adv Ecol
Res 18: 1-63
Chazdon RL, Fetcher N (1984) Photosynthetic light environments in a lowland tropical
forest in Costa Rica. J Ecol 72: 553-564
Chazdon RL, Pearcy RW (1986a) Photosynthetic responses to light variation in rain forest
species. I. Induction under constant and fluctuating light conditions. Oecologia 69:
517-523
Chazdon RL, Pearcy RW (1986b) Photosynthetic responses to light variation in rain
forest species. II. Carbon gain and light utilization during lightflecks. Oecologia 69:
524-531
Farquhar GD, Richards RA (1984) Isotopic composition of plant carbon correlates with
water use efficiency of wheat genotypes. Aust J Plant Physioll1: 539-552
Farquhar GD, O'Leary MH, Berry JA (1982) On the relationship between carbon isotope
discrimination and intercellular carbon dioxide concentration in leaves. Aust J Plant
Physiol 9: 121-137
Kirschbaum MUF, Pearcy RW (1988) Gas exchange analysis of the relative importance of
stomatal and biochemical factors in photosynthetic induction in Alocasia macrorrhiza.
Plant Physiol 86: 782- 785
Miller E, Norman JM (1971) A sunfleck theory for plant canopies. II. Penumbra effect:
intensity distributions along sunfleck segments. Agron J 63: 739-748