Factors Associated with the Synthesis of Chlorophyll in the Dark in Seedlings of Pinus jeffreyi

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Abstract
Chlorophyll formation in the dark and certain relationships between the megagametophyte and sporophyte were studied in germinating seeds and excised seedlings of P. jeffreyi. Embryos excised from ungerminated seeds did not form chlorophyll when grown in darkness on certain extracts of megagametophytic tissues or synthetic media, but did form chlorophyll on these substrates in light. Sporophytes in intact seeds form chlorophyll in darkness and seedlings excised during the first few days after germination continue to form chlorophyll in darkness for a limited time. The total amt. of chlorophyll formed by excised seedlings after separation is a function of the preceding duration of contact between seed components during germination. The rate of chlorophyll synthesis in darkness after separation is also affected by the above as well as by temp. The temp. coeff. in the interval 11[degree]-23.5[degree]C is estimated to be 1.69. The availability of sucrose, Fe, and Mg did not affect synthesis of chlorophyll by excised seedlings. Excised seedlings exposed to 60 f.c. light during the 2 days following separation synthesized chlorophyll about 4 times more rapidly than similar seedlings kept in the dark, but at about the same rate as those remaining in contact with the megagametophyte. Ether-soluble Mg content was followed in another expt. Four days after germination 2.5% of total ether-soluble Mg of the sporophyte was attributable to that in chlorophyll; 6 days later this value was 35.2%. In separated seedlings continued in the dark on a nutrient medium the max. value attained was 22%.