The functional state of the photosynthetic apparatus of flowering homoiochlorophyllous desiccation tolerant plant Haberlea rhodopensis during dehydration and subsequent rehydration was investigated in order to characterize some of the mechanisms by which resurrection plants survive drought stress. The changes in the CO2 assimilation rate, chlorophyll fluorescence parameters, thermoluminescence, fluorescence imaging and electrophoretic characteristics of the chloroplast proteins were measured in control, moderately dehydrated (50% water content), desiccated (5% water content) and rehydrated plants. During the first phase of desiccation the net CO2 assimilation decline was influenced by stomatal closure. Further lowering of net CO2 assimilation was caused by both the decrease in stomatal conductance and in the photochemical activity of photosystem II. Severe dehydration caused inhibition of quantum yield of PSII electron transport, disappearance of thermoluminescence B band and mainly charge recombination related to S2QA- takes place. The blue and green fluorescence emission in desiccated leaves strongly increased. It could be suggested that unchanged chlorophyll content and amounts of chlorophyll-proteins, reversible modifications in PSII electron transport and enhanced probability for non-radiative energy dissipation as well as increased polyphenolic synthesis during desiccation of Haberlea contribute to drought resistance and fast recovery after rehydration.

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We provide the directed counterpart of a slight extension of Katoh and Tanigawa's result [9] on rooted-tree decompositions with matroid constraints. Our result characterises digraphs having a packing of arborescences with matroid constraints. It is a proper extension of Edmonds' result [1] on packing of spanning arborescences and implies -using a general orientation result of Frank [4] -the above result of Katoh and Tanigawa.We also give a complete description of the convex hull of the incidence vectors of the basic packings of arborescences and prove that the mimimum cost version of the problem can be solved in polynomial time.

Iron deficiency is a key factor in Cd-induced inhibition of photosynthesis.